Digest Published

September 2004

ii

Considerable effort has been taken to ensure the accuracy andreliability of the information contained in this publication. However,neither Sabita nor any of its members can accept any responsibilitywhatever for any loss, damage or injury resulting from the use orimplementation of this information.

The views and opinions expressed in this publication are those of the authors, and do not necessarily reflect the views of Sabita or any ofits members.

Vision

Mission

iii

Sabita’s plans and actions are consistent with good corporatecitizenship to underpin its dealings with government, and toassist its members.

Sabita will:

• advance best practice in southern Africa with due regard to worker health and safety, as well as the conservation ofthe environment;

• provide education and training schemes to develop skillsand competencies that are sustainable and aligned tonational goals and frameworks; and

• engage government to promote the social and economicvalue of road provision and efficient delivery by state roadorganisations.

Contents

Preface . . . . . . . . . . . . . . . . . . . . . . . . . 8

Sabita looks back on 25 years of progress and achievement . . . . . . 13Asphalt Academy: an effective education and training armLR Sampson . . . . . . . . . . . . . . . . . . . . . . 21Sharp upswing in SAT activities in all regionsJ Onraët . . . . . . . . . . . . . . . . . . . . . . . . 26

Introduction: CAPSA’04 gives new direction:. . . . . . . . . . 30

Human and economic resource development

Building capacity by mentoring mathematics and science teachersE Horak et al . . . . . . . . . . . . . . . . . . . . . . 39Sustainable provision of low-volume sealed roadsMI Pinard et al . . . . . . . . . . . . . . . . . . . . . 42The state of tertiary education in pavement engineering in South AfricaLR Sampson et al . . . . . . . . . . . . . . . . . . . . 48Infrastructure financing and provisionS Muradzikwa . . . . . . . . . . . . . . . . . . . . . . 53

Safe and Efficient Delivery

Monitoring bitumen quality from refinery to pavementSJ Emery et al . . . . . . . . . . . . . . . . . . . . . . 61Experiences with half-warm foamed bitumentreatment process in The NetherlandsJLM Voskuilen et al . . . . . . . . . . . . . . . . . . . . 64Whole of life costing – incorporating ownership issues and design riskRM Vos et al . . . . . . . . . . . . . . . . . . . . . . 69Bitumen occupational health – update on recent activitiesT Riley . . . . . . . . . . . . . . . . . . . . . . . . . 75European experiences with performance guarantee and/or product guarantee systemsM Démarre . . . . . . . . . . . . . . . . . . . . . . 78Clustering infrastructure development projects for optimal opportunity valueS Muradzikwa et al . . . . . . . . . . . . . . . . . . . . 82Bituminous based precoating fluid for surface dressingK Louw . . . . . . . . . . . . . . . . . . . . . . . . 84Overcoming compaction difficulties of crushed stone base materialby the addition of a very low percentage of bitumen emulsionAO Bergh et al . . . . . . . . . . . . . . . . . . . . . . 86

v

Labour-based bitumen roads as cost-effective alternatives toconventional gravel wearing coursesP Paige-Green et al . . . . . . . . . . . . . . . . . . . . 88Risk-managed design standards for upgrading of basic access gravel streetsE Horak et al . . . . . . . . . . . . . . . . . . . . . . 91

Design of Structures and Materials

A re-evaluation of some aspects of the mechanistic-empirical design approachFJ Jooste . . . . . . . . . . . . . . . . . . . . . . . 103Performance based road surfacing seal evaluation: empirical testingTI Milne et al. . . . . . . . . . . . . . . . . . . . . . 110Bitumen foaming - an innovative technique used on a large scale for pavement rehabilitation in AfricaC Overby et al . . . . . . . . . . . . . . . . . . . . . 115Determination of stress- dependent material properties with the FWD for use in the structural analysis of pavementsSJ Bredenhann et al . . . . . . . . . . . . . . . . . . . 118The effect of axle load spectra and tyre inflation pressures on standard pavement design methodsBS Morton et al . . . . . . . . . . . . . . . . . . . . . 121Effect of asphalt mixture compaction on aggregate orientation, segregation and mechanical performanceAE Hunter et al . . . . . . . . . . . . . . . . . . . . . 125A LTPP exercise on a foamed bitumen treated base on R504 in KwaZulu-NatalD Collings et al . . . . . . . . . . . . . . . . . . . . . 128Tyre-pavement interface contact stresses on flexible pavements — quo vadis?M de Beer et al . . . . . . . . . . . . . . . . . . . . . 132Concepts used for development of bitumen specificationsMFC van de Ven et al. . . . . . . . . . . . . . . . . . . 134Advanced testing for cold recycling treatment selection on N7 near Cape TownKJ Jenkins et al . . . . . . . . . . . . . . . . . . . . . 141Aggregate strength for bituminous surfacings for low volume roads: a heavy vehicle simulator experienceP Paige-Green . . . . . . . . . . . . . . . . . . . . . 144Mechanistic-empirical structural design models for foamed bitumen and bitumen treated materialsF Long et al . . . . . . . . . . . . . . . . . . . . . . 147Rehabilitation of runway at Johannesburg International Airport: selection of asphalt mixes using MMLS3 testingP Molenaar et al . . . . . . . . . . . . . . . . . . . . 151Correlations between different ITS and UCS test protocols for foamed bitumen treated materialsM Houston et al . . . . . . . . . . . . . . . . . . . . . 155

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A self-regulation initiative to address the heavy vehicle overloading problem in South AfricaPA Nordengen et al . . . . . . . . . . . . . . . . . . . 159

Member contributions

Specialised ultra-thin asphalt friction courses for southern AfricaFJ Pretorius et al . . . . . . . . . . . . . . . . . . . . 167Pre-fabricated road patches for routine and emergency road maintenanceM Church . . . . . . . . . . . . . . . . . . . . . . . 171The use of bituminous slurry for shoulder protectionTR Distin . . . . . . . . . . . . . . . . . . . . . . . 174New generation modified binder used in KwaZulu-NatalTR Distin . . . . . . . . . . . . . . . . . . . . . . . 180Colas on the road for 75 years ... and still countingTR Distin . . . . . . . . . . . . . . . . . . . . . . . 184The seal that has stood the test of timeTR Distin . . . . . . . . . . . . . . . . . . . . . . . 187

Author Index . . . . . . . . . . . . . . . . . . . . . . 190

Sabita/Asphalt Academy Manuals . . . . . . . . . . . . . . . 192

Sabita Video Series . . . . . . . . . . . . . . . . . . . . 193

vii

Preface

Published annually by Sabita for the past five years, the Digest is anongoing overview of technological advance, system changes, and overall progress in Sabita’s drive to develop and upgrade standards of practicein southern Africa’s bituminous products industry. CAPSA, over theyears, has been a valuable partner in this process, and in fact theformation of Sabita was announced at CAPSA’79.

Since CAPSA’04 at Sun City coincides with Sabita’s 25 th anniversary, wethought it appropriate to feature in this publication papers accepted forthe conference — papers which, in our opinion, are noteworthy inoffering direction to the industry. As in the past, members’ contributions have also been invited, and these are included.

We gratefully acknowledge the valuable contribution of Professor KimJenkins of the SANRAL Chair at the University of Stellenbosch. Aschairman of the CAPSA’04 technical committee, he was able and mostwilling to give his guidance and assistance in the editing process.

Due to space constraints, only a certain number of selected CAPSA’04papers could be accommodated in this publication, and readers areurged to consult the conference agenda for acomprehensive list of valuable material presented.

ix

Piet MyburghExecutive Director

Sabita

Engen Ad

xi

The Southern AfricanBitumen Association(Sabita) celebrates its

25th anniversary in 2004 froma position of unprecedentedstrength, respect andinfluence.

The organisation’s achievementssince its launch at CAPSA’79 inDurban are the result of aconscious commitment to ongoinganalysis, adaptability, and theactive participation of itsmembers in formulatingand pursuing theassociation’s strategicobjectives.

Sabita has achieved itspositive status in theblacktop roads industry —both locally andinternationally — throughvigilant perception of thevolatile socio-economiclandscape of southern Africa ingeneral, and of the region’sbituminous products industry inparticular. Central to the processof satisfying these needs has been the organisation’s willingness tobe flexible, to form partnershipsand alliances with road industrystakeholders, and to align itselfwith the key objectives ofgovernment policy makers.

In establishing the SouthernAfrican Bitumen and TarAssociation (Sabita) in 1979, theblacktop roads industry sought tocreate a proactive mechanismwhich would build a framework ofopportunity for the structured andunified development of thebitumen market. Closely linked tothis was the objective of unitingSabita members in their commongoals, and of promoting efficiency, profitability and best practice.

AREST

In its early years Sabita’sprimary focus was ontechnology developmentto broaden the marketbase for its members, and to render their productsand services cost-effective and competitive. Much of this effort waschannelled through the

Sabita-sponsored AsphaltResearch Strategy Task Force(AREST), established in 1987.

While these objectives wereappropriate to the needs of Sabitamembers, and to the market,during the years 1979-1987,Sabita’s strategic goals have beenradically adapted to perceivedneeds since then, underlining the

13

Sabita looks back on25 years of progressand achievement

Founding ChairmanPeter Faure

1979-1982 and1985-1987

association’s flexibilityin the face of rapidlychanging social andeconomic conditions.

Strategic objectivesidentified by Sabita’sCouncil at that timeenvisaged that Sabitawould:

• Be an “ongoingCAPSA to bridge the gap between thefive-yearlyconferences byproviding forums fordiscussion onmatters relevant tothe blacktopindustry;

• Represent theindustry oncommittees thatguide the design and construction ofroads;

• Access overseasexpertise andexperience byforging links withinternational sisterorganisations; and

• Represent theinterests of itsmembers in thepublic media.

These goals wereregarded as “ambitious but attainable”.

Sabita’s activities were funded exclusively bymember subscriptionsuntil 1987. In that year the association took aquantum leap forward

when the oil companies committed themselves to funding research, achair of learning (StellenboschUniversity) and other activitiesdesigned to entrench globalstandards in South Africa’sblacktop roads industry.

This needs-driven research, asidentified by AREST, led to theformalisation of generictechnologies such as LAMBS,GEMS, and ETB, and thedissemination of this knowledge in published technical manuals.

Economic guidelines promotingefficient delivery, such as Manual7: SURF+ Economic warrants forsurfacing roads, were alsodeveloped and published.

This manual is currently beingupdated to align its recommen-dations with current economicimperatives.

In all, Sabita has published 23technical manuals, three trainingguides and 21 supportiveaudio-visual aids, and thesepublications have becomeentrenched in university andtechnikon curricula.

CAPSA Secretariat

As part of its service to theindustry, Sabita undertook tomanage the CAPSA secretariat in1980, and performed this functionbetween then and CAPSA’99 atVictoria Falls, Zimbabwe. 1989 also saw the appointment of aTechnical Manager (later Technical Director) to oversee the directionand development of relevanttechnologies, publications,

14

Wally BabbChairman

1988-1992and

HonoraryLife

Member

Dave Orton Chairman1993-1997

andHonorary

LifeMember

DaanStiglinghChairman

1998-2003and

HonoraryLife

Member

PhilipHechter

Chairman2004 -

educational material, seminarsand workshops, the founding ofthe Society for Asphalt Technology (SAT) under the auspices ofSabita, and ongoing researchprojects.

Although technology developmentremained a major focus for thenext several years, attentionincreasingly shifted towards socialdevelopment issues, includinghuman capital development toensure an informed industrystaffed by informed practitioners.

Asphalt Academy

This new focus led to the evolution of the Asphalt Academy (AsAc), aSabita-CSIR Transportek jointventure under CEO Les Sampson.Launched in 2001, AsAc wastasked with delivering well-trained and educated practitioners to theasphalt and bituminous productssector in southern Africa. Inaddition to developing andpresenting a comprehensive range of training courses, workshops and seminars, AsAc has developedlearnerships in line with therequirements of the SkillsDevelopment Act, convened andmanaged research programmes on modified binders and foamedbitumen treated materials, andpublished technical guidelines.

Despite its relatively short periodof existence, AsAc is currentlyrecognised as the premier centreof learning for the blacktop sectorin southern Africa, and isdeveloping strategies to extend its influence into the Southern African Development Community (SADC).

The reformulation ofthe BituminousMaterials LiaisonCommittee (BMLC) in1990 into a moreinteractive forum,co-sponsored by Sabita and the CSIRTransportek, created afertile environment forthe evolution ofrelevant strategicdirections for theblacktop industry, andensured lively debateand knowledge sharingamongst the industry’sleading practitioners.

The BMLC later evolvedinto the RoadPavements Forum (RPF) with expandedsponsorship, whichincluded representatives of the cement andconcrete sector, and the quarrying andaggregate supplyindustry.

In 1993 Sabitainstituted the SabitaChair in AsphaltPavement Engineeringat StellenboschUniversity, whichestablished thenecessary contact toensure that civilengineering courses attertiary institutionsgave appropriateemphasis to flexiblepavement engineering,and to promotepostgraduate studies in

15

RonnyRenshaw

1989Excellence

Award

SteveEmery1991

ExcellenceAward

EmileHorak1992

ExcellenceAward

Chris Rust1992

ResearchAward

Etienne deVilliers1993

ExcellenceAward

flexible pavement engineering.

Integrated activities

During the late 1980s and early1990s it also became apparentthat if Sabita were to functioneffectively on behalf of itsmembers, and at the same timeexert meaningful influence on thedevelopment of both the regionaleconomy and the blacktopindustry, it would need tointegrate its objectives with thoseof the broader economy.

This perception was underlinedwhen new directions, identified byRE-AREST in 1991, gave rise to aproject entitled Social Develop-ment Issues affecting Roads andRoad Transportation. This newfocus on the value of roads in thedevelopment and upliftment ofSouth Africa’s underdeveloped

areas increasingly influencedSabita’s strategic decision making.Challenge analysis in the early1990s made it clear that, in theface of a rapidly changing politicalclimate as South Africa movedtowards a functional democracy,Sabita would achieve greatervalue for it’s members by fostering an environment of constructiveengagement with government and roads authorities. The discovery,by a Sabita funded study, that 220 000 km of roads servingtownships and remote rural areaswere not on the state’s inventory,refocused the state in their questfor proper asset management.

One initiative driven by the needfor more efficient delivery was theSabita-sponsored Roads DevelopPeople programme [laterre-named the CouncillorEmpowerment Programme (CEP)],

16

0%

20%

40%

60%

80%

100%

1988 1989 1990 1991 1992 1993 1994 1995 19961997 1998 1999 2000 2001 2002

Relative allocation

Government Contact

Education and Training

Technology Development

Sabita’s evolving strategic focus is illustrated in the changing patternof resource allocation shown above

instituted in 1997. More than 1 200 local government councillors attended interactive workshops on the assessment of roadconstruction and maintenanceneeds in their constituencies, andon budgeting, fund allocationprocesses and other managementskills. This highly successfulempowerment programme wassupported by the SA Departmentof Transport and the United States Federal Highway Administration.

A natural evolution of thisprogramme was the formation ofSabita’s Urban Renewal andRural Development (URRUD)focal point. This group, led byvice-chairman Daniel Mashatolaand representative of the broadbituminous products industry, hasreviewed and updated the RoadsDevelop People programme in2004 to align it with structuralchanges within the various localand provincial governmentsectors.

Central to the revised programmewill be workshops focussing on the socio-economic benefits ofadequate roads, road engineeringprocesses and terminology, theimportance of asset management,employment opportunities in roadconstruction and maintenance,rational decision making, andbusiness and implementationplanning.

In a significant shift in strategicdirection in 1996, Sabita droppedthe word “Tar” from its name andbecame the Southern AfricanBitumen Association (Sabita), with the primary objective of promoting excellence in the use of

bituminous products.Closely linked to thisshift was a broadenedstrategic frameworkembracing not only core technologydevelopment, but alsomarket development,national norms andstandards through thenational Task Force onSpecifications forBituminous Products,and a re-alignment withconcerns for workersafety health, andenvironmentalconservation.

The focus on HSE issues gathered momentumover the next six years,culminating in thelaunch of Sabita’sCentre for Health and Safety and Environ-mental Conservation(COSHEC) focus groupin 2003. COSHEC hasundertaken to developguidelines aimed atprotecting workerhealth and safety, andto develop policies(based on globalconventional wisdom)to protect the environ-ment. Focus areasinclude:

• Delisting by theDepartment ofWater Affairs andForestry (DWAF) of bitumen as ahazardous waste;

• Safe workingpractices;

17

ChrisPotgieter

1995Excellence

Award

John Gregg 1994

ExcellenceAward

BenoitVerhaeghe

1995Research

Award

Martin vande Ven1997

ExcellenceAward

BasieNothnagel

1996Excellence

Award

• Bitumen safetytraining;

• Handling ofbituminous products in transport andstorage;

• Alternativetechnology to coaltar products.

It is anticipated thatCOSHEC will becomethe instrument through which the bituminousproducts industry willact proactively in aself-regulatory mannerto ensure that policiesadopted andimplemented areup-to-date, relevantand representative ofglobal best practice.

National awareness

However, while Sabitacontinues to drivetechnology, education,safety and marketdevelopment initiatives, its most importantoverall objectiveremains to inculcate anational awareness of the cruciallink between adequate roads andsocio-economic development.

The association’s Public PolicyAwareness Campaign , whichhighlighted relevant issues inprint, radio and television media,achieved a major breakthrough in2000 with the publication of aSabita-funded academic report onthe funding of infrastructure in the public sector.

Drawn up by a team headed byProfessor Don Ross of theUniversity of Cape Town, theso-called Ross Report — The

18

Growth in Sabita membership

Sabita Membership

0

10

20

30

40

50

60

TrevorDistin1998

ExcellenceAward

DennisRossmann

2001Excellence

Award

ElzbietaSadzik2002

ExcellenceAward

LesSampson

2003Excellence

Award

under-provision and under-capitalisation of roadmaintenance, rehabilitation andupgrading in South Africa —underlined the potential capitalappreciation accruing to off-roadassets through infrastructuredevelopment.

The converse — loss of benefit tooff-road assets when roadinfrastructure is inadequate — was given equal emphasis.

The report also challenged theappropriateness of conventionalcost benefit analysis (CBA) inprioritising infrastructure needs ina country with such wealthdisparities as South Africa.

Ongoing projects

The publication of the Ross Report led to significant meetingsbetween representatives of thebituminous products sector, theMinister of Transport and theParliamentary Portfolio Committee on Transport. It also resulted in acooperative venture by the SouthAfrican National Roads Agency(SANRA) and Sabita to set upprojects for the development of an Opportunity Value Assessmentmechanism suitable for use inSouth Africa.

Opportunity Value Assessment(OVA) measures the costs savedon maintaining a primarynon-roads asset by investing ingood roads, and the contribution

to the value of theprimary asset as aresult of its beingserviced by goodroads. These projectsare ongoing.

The Ross Report hascontributed to muchmore positivecooperation betweenSabita and both thepublic and theauthorities, whorecognised that Sabitamembers were abovesimple self-interest,and were committed to finding viable solutions to the socialdevelopment problems

inherited by thecurrent regime.

A graphic indicator ofSabita’s prominentstature and influencein post millenniumSouth Africa is itsmembership, which isstronger and morebroadly-based than atany time in the association’s25-year history. This membershipgrowth was fostered by thedecision in 1996 to include theconsulting engineering sector inthe association’s membership, buta powerful influence attractingnew members has been therecognition within the broad roadsindustry, and in the bituminousproducts sector in particular, that

19

Sabita’s membership is now stronger and more broadly-basedthan at any time in the association’s 25-year history

Max Pike Honorary

LifeMember

GarthGreen

HonoraryLife

Member

BobKingdonHonorary

LifeMember

it is within Sabita’s power to make very positive impacts on thedevelopment of the industry, andthereby to promote the interestsof Sabita members and of theireconomic region. Sabita’s 25-year

track record, often in the face ofsevere restraints and difficulties, is a vivid confirmation of theassociation’s success andachievement in fostering a robustand innovative industry.

20

W ith tenindustry-definedcourses developed by

the end of 2002, AsAc’sprimary focus in 2003 shiftedto the transfer of knowledgethrough course presentationusing CETA-accreditedpresenters whenever possible.

The schedule of courses developed and presented by Tjeka (see Table 1) related to specific unitstandards. A decision was taken at the start of the year to run all the

courses outlined on the schedulein order to evaluate the need forthe various courses, and theresponse of the market based onthe increased importance beingplaced on courses forming part ofunit standards/qualifications.

A total of 48 courses has beenscheduled for presentationnationwide in 2003/04. In addition to these, a very successfulthree-day advanced bitumencourse was also organised inassociation with the SANRAL Chair

21

Asphalt Academy: an effectiveeducation and trainingarm

LR Sampson Asphalt Academy

Asphalt Academy courses available for presentation in 2003/2004

Course Presenter

Introduction to bitumen L Sampson

Application of seals Tjeka/J Beukes

Application of hot-mix asphalt Tjeka/J WiseManufacture of hot-mix asphalt Tjeka/G Miller

Pavement repair and maintenance (LIC) Tjeka/Industry providers

Bituminous surfacings (including LIC) Tjeka/Industry providers

Design of surfacing seals/modified binders G van Zyl/L SampsonDesign of hot-mix asphalt B Verhaeghe

Asphalt testers’ course — Modules A, B, C Pretoria TechnikonCape TechnikonDurban Institute of Technology

Bituminous Materials on Site (BMOS) Pretoria TechnikonPeninsula Technikon

Advanced bitumen course H Bahia, University of Stellenbosch

Compaction of HMA (SARF module) J WiseTable 1: AsAc courses available for presentation in 2003/2004

in Pavement Engineering at theUniversity of Stellenbosch,featuring international guestlecturers from the universities ofWisconsin (Hussain Bahia) andDelft (Professor Martin van deVen).

A new strategy, based on thesuccesses of 2003/04, will bepursued in 2004/05. This willinvolve the formation of strategicalliances and partnerships withother industry groupings and client bodies to further streamline andimprove the efficient delivery ofcourses in the future.

Block course

AsAc’s role in supporting tertiaryinstitutions in 2003/04 took theform of a comprehensive survey of curricula, courses and resourcesrelevant to the road industry. Theresults of the survey will bepresented in a joint paper with the SANRAL Chair at CAPSA‘04.

However, based on the findings ofthe survey, one of the majorinitiatives for 2004/05 will be thedevelopment of a block course inflexible pavement engineeringtargeted at newly qualified civilengineers and technicians entering the roads industry. Some of thesurvey findings included:

• A major problem lies withinterpretation ofunder-graduate andpost-graduate courses atTechnikons compared withthe Universities, and a clearer definition will need to bedeveloped;

• The number ofundergraduates exposed topavement engineeringappears to have increasedsince 1999 (average increase 8%/year to 2002). However,it is of concern that onlybetween 15 and 20% of postgraduate civil engineeringstudents are specialising inpavement engineering;

• The number of lecturers atpost-graduate levelspecialising in pavementengineering is a concern;

• Pavement engineering is notspecifically offered at B Techlevel at Technikons. Theindustry should consideractively promoting pavementengineering as a B Techcourse or AsAc shoulddevelop a block course tointroduce newly qualified civil engineers, technicians andtechnologists to flexiblepavement engineering;

• Equipment available forspecialised research attertiary institutions isconsidered to be ad hoc andgenerally limited. This is seen as an added problem inattracting students tospecialise in pavementengineering.

Major gaps

A survey of industry trainingneeds, carried out during2003/04, identified two majorgaps in the current portfolio ofcourses. These were on bitumenstabilisation (either using emulsion or foam) and a specialist courserelated to health, safety and

22

environmental issues applicable to the bituminous products sector. Itis anticipated that for the next two years, most of the feedback in this area will be presented in ad hocworkshops and seminars tofeedback the latest best-practiceguidelines as they are developedand published. A course onbitumen stabilisation could bedeveloped for subsequent yearsonce the latest technologies areaccepted and refined in practice.

A proposal to develop a course fortrainers was also received. This isconsidered to be priority area andwill need further attention in2004/05.

Guidelines

AsAc has also managed work onthree new best-practice guidelinedocuments throughout the year.These are related to emulsion-treated materials, thin asphaltsurfacings, and a practical guide to hot-mix asphalt design. Theseguidelines are likely to bepublished as part of AsAc’s TGseries during 2004/05, and will befed back to industry throughregional workshops and seminars.

For the coming year AsAc plans toensure that courses and curriculaoffered at institutions of learningare consistent and relevant toindustry needs through:

• Regular assessment of course curricula;

• Providing relevant knowledge transfer to lecturers, trainersand learners.

In collaboration with tertiaryinstitutions, AsAc will also ensurethat advanced courses andpost-graduate studies are properly scheduled, coordinated andaligned with relevant legislationand quality standards.

Teaching will take the form of:

• Seminars and workshops todisseminate best practice;

• Publication and distribution of manuals and technicalguidelines;

• Management andmaintenance of appropriateinformation systems;

• Support for and participationin CAPSA and RPF activities;

• Support of Sabita and CSIRTransportek courses andinitiatives within South Africaand into SADC countries

Other areas identified for AsAcaction in 2004-05 include:

• Development of a FlexiblePavement Engineering blockcourse for presentation atTechnikons. The initialdevelopment will be inassociation with Vaal Triangle Technikon;

• Optimisation and rational-isation of the courseschedule;

• Development of a qualitymanagement system for the

23

The development of a course for trainers is considered to be anAsAc priority area

24

ongoing evaluation ofcourses;

• Development of a strategicalliance with KwaZulu-NatalDoT for better marketing and promotion of courses in thatprovince;

• Development of strategicalliances with institutions oflearning/training providersoffering learnerships relevant to the roads and bituminousproducts industry;

• Targeting of specific clientauthorities to identify specific course and programmes fortheir areas. The Free State,Limpopo, Mpumalanga andthe Eastern Cape areidentified as target areas forthe next financial year;

• Development of a strategicalliance with SAT to bettermarket ad hoc seminars andworkshops for ongoingpractitioner development;

• Development of a strategicalliance with SARF;

• Further develop an allianceand operationalunderstanding with T-squared centres as appropriate;

• Obtain CETA recognition/registration for AsAc coursematerial relevant to specificunit standards;

• Develop and incorporate aHSE course into the AsAcportfolio in line with Sabitarequirements;

• Present seminars/workshopsof the latest technicalguidelines related to: • Ultra Thin Asphalt;• EBTM guidelines;• SA HMA practical

guidelines;• Binder distributors;

• Develop a proposal forpresentation of courses inNamibia for submission to the Namibia Road Authority;

Course 2001/2002 2002/2003 2003/2004

No. of courses

Atten-dees

No. of courses

Atten-dees

No. of courses

Atten-dees

Introduction tobitumen

11 204 4 49

Application ofsurface seals

2 43 4 50

Asphalt Testers’ Course (ATC)

7 72 7 63 8 76

Bituminousmaterials onsite

1 8 1 5

Application ofHMA

4 54

Design of HMA 3 49

Design ofsurface seals

2 37

Advancedbitumen course

1 38

TOTALS 7 72 21 318 27 358

Table 2: AsAc courses and attendances

• Develop strategic alliances toopen up other SADCmarkets;

The role and profile of AsAc is now well established and growing inSouth Africa, and attendance atAsAc courses has shownconsistent growth over the pastthree years (see Tables 2 and 3). Strategically, it is now an idealtime to gather new ideas forsubsequent years to ensure thatAsAc maintains and improves itsservices to the industry. With thisin mind, attendance atinternational conferences such asthe Eurobitume/EurasphaltCongress in Vienna in May 2004,

and CAPSA’04 At Sun City, is seen as important. Gatheringinformation on new internationalactivities and innovations,especially related to education and training and ongoing practitionerdevelopment that could beintroduced into South Africa, is avital element in AsAc’s ongoingability to satisfy industry needs.Particular attention in the shortterm will be given to thedevelopment of a course based on Health and Safety issues, basedon the new Sabita Manual 8:Guidelines for the safe andresponsible handling of bituminous products.

25

Publications andWorkshops

Date of Workshop Attendees Publication sales

TG1: ModifiedBinders Guideline

October 2001 249 889

TG2: FoamedBitumen

September 2002 256 970

TRH3 HMA design June 2001 319

TRH3/HMAdesign/Modifiedbinders

March 2002 51

Ultra-thin layerasphalt

May 2002 75

TOTALS 950 1859

Table 3: AsAc publications and feedback workshops

Only one change tookplace in the nationalcouncil during the past

year, and that was theresignation of BenoitVerhaeghe as HonoraryTreasurer. This post is nowheld by Elzbieta Sadzik, whocontinues to exert firm controlover the finances of theSociety.

The four regional chairpersons —Gary Swart (East), Renaldo Lorio(South), Basil Jonsson (Central)and Duncan Smith (North) — aswell as our Honorary Secretary(Duncan Mason) and two ex-officio members (Piet Myburgh and LesSampson), remain unchanged and make up the balance of theCouncil.

Renaldo Loriohas relocated toPort Elizabeth,and Julian Wisehas temporarilytaken respon-sibility for theSouthern Region until the nextlocal AGM. My

sincere thanks go to Renaldo forhis valued contributions to theSouthern Region. The good news

is that, withRenaldo now inthe EasternCape, he hasindicated that he is in a positionto set up a newregion, aterritorial gapwhich has longbeen recognised by council. The day to day administration ofthe Society continues to bemanaged extremely ably by PatLoots. How she does it is nothingshort of miraculous, as she alsoworks for the Asphalt Academy,and in addition, is the Secretaryfor the CAPSA’04 conference inSeptember 2004. Nevertheless,she has done amazingly well andmy personal thanks go to her forall her hard work in keeping it alltogether.

Strategic issues

Council has thus been able todevote its attention to suchstrategic issues as:

• encouraging regionalactivities;

• propagating the image of SAT (eg the website);

• membership growth;

26

Sharp upswing in SAT activitiesin all regions

J Onraët President

Society for Asphalt Technology

• marketing the aims andobjectives of SAT;

• ensuring the correct balancein the relationship withAsphalt Academy;

• financial transparency andstability;

• promotion of SAT insub-regions.

Finance

SAT is a completely self-sustaining organisation, and relies exclusively on the prompt payment ofsubscriptions, as well as incomereceived from activities of theregions.

The cost of annual subscriptionshas only been marginallyincreased since the inauguration of the Society, the principle beingto attract membership from alllevels of the asphalt industry, andto make membership affordable to all.

Regrettably, there are still anumber of delinquent memberswho have just not paid timeously,

— and some who are evenseriously in arrears. Elzbieta willbe resolving this issue (hopefullyamicably) in the coming months.

The income from subscriptionsalone is insufficient to cover therunning costs of the Society, andCouncil therefore proposes toincrease subscriptions by 12%from January 2005. The financialviability of the organisation will,

however, still rely on regionalactivities.Regional Activities

Over the past eighteen monthsone of the fundamental challenges facing SAT has been that ofdelivery to its members, and I amvery pleased to report that allregions have made significantprogress towards this goal — dueentirely to the energy inputs of the regional committees.

Central Region:The CentralRegionCommittee, under the leadership ofBasil Jonsson, ismade up of ahealthy crosssection of industry sectors:

• Basil Jonsson, bitumensupplier;

• Joe Grobler, consultingengineer;

• Rob Brown, consultingengineer;

• Tom van Rijckevorsel, hotmix asphalt supplier;

• Morris de Beer, researcher;• Hennie Kotze, client body; • Emile Horak, educational

institution;• Enrico Fletcher, client body;• Chris de Jager, educational

institution;• Piet Fourie, materials

laboratory manager.

27

The fundamental challenges facing SAT has been to ensuredelivery to its members

This committee has been busyover the past twelve months or soorganising the following:

• Asphalt EnhancementTechniques at the Edge of the Performance Envelope —Discrete Elements (workshop);

• Quality Control of FoamedBitumen-treated Materials (workshop);

• Site visit to national refineries (Natref);

• Factors InfluencingPremature Ageing inBitumen: The USA Experience (technology exchangesession);

• Current challenges in theasphalt industry: Crackingand Rutting of SA Roads(workshop). This successfulworkshop is scheduled to berepeated in all other regions.

An average of 120 peopleattended the various functions,and the refinery visit was totallyoversubscribed.

This region, being closest to theCAPSA’04 conference venue, hastaken responsibility for arrangingthe SAT Golf Day at Sun Cityduring the conference.

Eastern Region: The EasternRegion, under the able

chairmanship ofGary Swart, isalso made up of a good blend ofpractitionersrepresenting awide spectrum ofindustry sectors:

• Gary Swart, consultingengineer;

• Daryl Jorgensen, hot mixasphalt producer;

• Craig Bradley, consultingengineer;

• Stuart Anderson, consultingengineer;

• Bob Hornsey, bitumensupplier;

• Barry Nothard consultingengineer;

• Keith Paul, educationalinstitution;

• Krishna Naidoo, municipalengineer;

• Veejay Ori, consultingengineer;

• Mark Evans, materialslaboratory manager;

• Barry Blunt, bindersproducer.

Gary Swart reports that a numberof seminars and workshops wereheld in this region, withattendance averaging 55 peopleper session.

Notable events were:

• Rehabilitation of 19 km of N2Illovo Road — Mlaas Canalusing Novachip (case study);

• Use of Salvicium in therehabilitation of UmgeniRoad/Argle Road intersection(case study);

• Recycling of Recycled Asphalt Pavement (RAP) material toform a paver laid base in theMobile KMA 200 (reportback);

• Safe Handling of BituminousProducts workshop;

• Paving Fabrics and Grids inAsphalt Overlays workshop;

28

• Ultra-thin surfacing on N1(case study);

• Blacktop roads for developing communities usingappropriate technology;

• Reseal of N2/27 & 28 usingSE-2 binder New Guelderland to Munzini Contract (reportback);

• Ultra-thin friction course onN7 (case study)

Some activities planned for thenear future are:

• Proposed revisions to TRH3;• Use of manually operated

chip spreader for labourbased construction of asurface seal;

• Constructability of asphaltsurfacing.

Southern Region: Julian Wise,who asmentioned, isacting regionalchair, reportsthat...

“... thededicatedSouthern Region Committee,together with

our highly supportive presenters,members and visitors, once againproduced a very active,stimulating and successful year.

The main emphasis was to provide events that were relevant to ourindustry in the region, and thatwould stimulate debate, under-standing and be a learningexperience. In addition, the socialinteraction and networking wasregarded as equally important.

Highlights of the year startingfrom April 2003 were:

• Five half day workshops inour highly successful“Understanding” series;

• Hot-mix asphalt — casestudies of specific problemprojects;

• Seal work — raw materials;• Seal work — overall design

considerations;• Seal work — specific design

of different seals;• Seal work — construction.

Attendances at these workshopsaveraged 120 people, and theexcellent presenters came from all over the country. We were alsovery grateful to have generoussponsors from the industry for therefreshments, thus allowingattendance fees to be verymodest.

Two more workshops on cold insitu recycling are arranged forAugust and October (steering wellclear of CAPSA’04).

Two “Cocktail Hour” presentationswere held. These very enjoyable,shorter, more informalget-togethers attract an averageof 30 to 40 people. Discussionsincluded:

• A simple tool for estimatingthe compaction window timefor HMA;

• The asphalt anomalies ofsome older Cape roads.

An interesting half-day site visitwas arranged to the N7 reha-bilitation project where the specific focus was on the bitumen rubber

29

asphalt overlay and ultra-thinfriction courses.Financially, the Southern Regionremained well in the black. Sowith this in mind, we decided toproduce a booklet as a useful toolfor the members. “A TroubleShooting Guide for HMA Paving”will shortly be published anddistributed under the SAT banner,although potential sponsors arestill being sought. Many thanks toall those who contributed to andreviewed the booklet.

A feather in the cap of theSouthern Region was that, of theten SAT Fellows that werenominated this year, six werefrom this region. Congratulationsto you all.

Our extremely committed and

hard working Chairman, RenaldoLorio, took up a new position inPort Elizabeth a couple of monthsago. His dedication and capacityfor work has been an example tous all. We sincerely thank him and wish him well in his new post.

Lastly, many thanks to all thecommittee members for theteamwork and great spirit. Yourefforts have been well recognised.

Northern Region: Under-standably, and for obviousreasons, the Northern Region(with its base in Harare) has notbeen as active as Duncan Smithwould have liked. Let’s hope thatthis region can restart activities in

the not-too-distant future when amore temperate industry climateprevails.

Membership

SAT membership currently standsat 495, of which there 18 arecurrently fellows. Nominationshave been received and approvedfor the appointment of 12 newfellows. These appointments willbe announced at CAPSA’04.(Remember it was at CAPSA’94that SAT was officiallyinaugurated, so SAT and CAPSAare inextricably linked).

Official membership cards arecurrently being produced by Patand will be sent to members as an accompaniment to the receipt ofsubscription payments.

There is a list of “untraceable”members, and we are planning toput their names on the website inan attempt to find them.

The future

It is my fervent hope that thenewly elected regional committees and Council for 2005 will maintaincontinuity in the activities anddeliverables to members. Inparticular, I would like to see theofficial formation of an EasternCape Region, and I am assured ofmuch support in this ambitionfrom Renaldo Lorio and otherindustry individuals in that area. It is envisioned that this could be the proto-type for other new regions.

30

We are assured of support from Renaldo Lorio and others in theformation of an Eastern Cape Region of SAT

The financial situation of theSociety remains a concern, andwill be a primary focus for thenear future — bearing in mind that the society is registered as aSection 21 company, operating ona non-profit basis.

I am also concerned that notenough use is being made of theSAT website. This is an extremelypowerful tool and affords members an opportunity to post news andopinions. A very positive opinionon our site was submitted by KimNeaylon, an engineer with theSouth Australian Government, and I encourage all members to do the same.

SAT has made its mark at theCAPSA’04 conference, byarranging the SAT Golf Day. I amconfident that we will have acomplete sell-out and that theevent will be remembered formany years to come.

“Finally, my sincere thanks — tomy Council, all of whom havegiven me their utmost loyalty andsupport during my two yeartenure as President of the Society. I know that together we have laidthe groundwork for a stable future for our organisation and to all theloyal members of SAT — pleasecontinue to support this worth-while learned society.”

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Tosas ad

33

35

Introduction:

CAPSA’04 gives new direction:

In this section we present extracts of selected papers which we believewould be of particular interest to readers. These extracts have beengrouped into categories that do not necessarily coincide with theconference session titles. Rather they are grouped in terms of themesthat reflect, in our view, key focus areas pertinent to the future direction of the roads industry.

We hasten to add that this section is not intended as an expedientmeans of coming to terms with the conference proceedings. Of necessity many papers of significant value have not been included in this section,and we should also stress that what appears here are selected sectionsand diagrams or tables that illustrate the main thrusts only. Readerswith an interest in the subject matter are therefore strongly encouragedto read the entire paper.

Readers should also note that tables and diagramsin this publication are not numbered sequentially.To avoid confusion, note that tables and diagramsare numbered as in the original papers.

Professor Kim Jenkins,Chairman, CAPSA’04Technical Committee

and co-editor.

’

37

Human

and economic

resource

development

’

39

The number of students incivil engineering hasdeclined steadily in South

Africa for the past decade. Atsenior schools Grade 12 figures have not only declined steadilyin over the past 5 to 8 years(550 000 in 1998 to 450 000 in 2002), but the proportion oflearners with mathematics and science at the higher grade has remained at very low levels.

This paper reports on investiga-tions into these problems, whichcan be broadly grouped into issues linked to language of tuition,learner specific socio-economicalsituations and also to issues

influenced by the attitude, level ofqualification and competence ofteachers. Recent outreachactivities have confirmed that themost cost-effective way in makingan impact on this problem seemsto be by concentrating on theteachers. One recent initiative inthis direction is the TeachersMentorship Programme (TMP),which was developed by theUniversity of Pretoria, using senior

mentor teachers to giveassistance to these teachers intheir school during school time.

While indicators such as thelanguage of tuition and thesocio-economic situations oflearners are important andwarrant an in-depth discussion,the most valuable observationsare those regarding the influenceof mathematics and scienceteachers on the performance oflearners. These teacher relatedobservations are:

• Approximately one in fourmathematics teachers werenot formally qualified to

teach mathematics;• South African teachers spent

excessive time re-teachingtopics that should have beencovered at lower levels;

• The more time that teachersspent preparing lessons after school, the better the learners scored inmathematics;

• Teachers’ pedagogical beliefs about mathematics were a

Building capacity by mentoringmathematics and scienceteachers

E Horak I FrickeUniversity of Pretoria University of Pretoria

The most valuable observations are those relating to theinfluence of teachers on the performance of the learners

Extract from CAPSA‘04 paper:

highly significant predictor ofachievement;

• The time spent by teachers in total at school was highlysignificant in predictinglearners’ achievement;

• The poor performance bySouth African learners maybe influenced by the lowexpectations of teachers.

Even though national governmentand various forums of role-players are addressing this issue ofscience and mathematics teaching at schools, the extent of theproblem requires all stakeholdersto contribute. The engineeringprofession clearly has too much at stake for it to reason that it is aproblem that needs to be sortedout by the minister of educationand departments of education.

Mentoring

Increasing awareness that greatereffectiveness and efficiency inpromoting mathematics and

science can be achieved byconcentrating on support for theteachers led to the development of the Teachers MentorshipProgramme (TMP). The TMPinvolves mentoring ofmathematics and science teachers at disadvantaged schools, inschool time, by experiencedmentor teachers. Short coursesand workshops away from theirown work have limited lastingeffect, often ignoring the reality of the teachers’ working conditions

and problems. Such intervention is designed to take place once aweek for at least a three-yearperiod to ensure sustainability.

The TMP concept was conceivedlate in 2002, and external fundingfrom corporate sponsors wassought from early 2003. Theintention from the start was tofirst run a pilot project in at leastfour disadvantaged schools in theGreater Pretoria (Tshwane) area,and the basic TMP concept wasimplemented at the BokgoniTechnical Secondary School inAtteridgeville in Tshwane in thesecond half of 2003.

Recommendations

The objectives of capacity building were defined as follows:

• Change educators’ mindset:assist them to seemathematics and science asnot difficult, just different;

• Help educators to understand

and apply the techniques ofteaching and learning;

• Assist each educator todevelop a portfolio ofevidence of professionalism;

• Motivate educators andrestore their confidence andself-esteem as a result ofbeing better informed;

• Restore educators’ belief inteaching and learning.

Although there has been no formal impact assessment to measure

40

The engineering profession has too much at stake to reason thatthis problem should be sorted out by the authorities

changes in teacher attitudes orabilities for this pre-pilot, there isanecdotal evidence to confirm that the four month TMP at Bokgonihas gone some way to achievingthe objectives as stated above.

The Bokgoni experience helped toidentify areas that neededattention to make the pilot project a success. The approach described and the lessons learnt clearly givean indication of activities andsteps needed to take make TMP asuccess. The TMP was envisagedas a franchise concept wherebylessons learnt could be packaged

like a recipe to be implemented atother schools with a high degreeof certainty that it will have apositive effect on learnermathematics and scienceeducation.

With research still ongoing, it isencourageing to note after onebridge building exercise, at leastfive black Grade 11 and 12 girlsindicated their enthusiasm tostudy civil engineering. Suchnumbers against the backgroundof the demographics of students in engineering is highly significant.

41

Good engineering practice, flexibility in approachand attention to various

sustainability factors arefundamental to thedevelopment of appropriateand economic designs forlow-volume sealed roads(LVR).

Much of road infrastructureinvestment is currently inrelatively low-volume secondaryand feeder roads as well as inproviding primary access. Thesetypes of roads typically comprisemore than 75% of the totalhighway system in most SADCcountries and impact on morethan 75% of the population thatlive in rural areas and depend onreliable access for theirlivelihoods.

Financial/economic issues

• Gravel is a sacrificial,“wasting” layer that is beingrapidly depleted;

• The cost of periodicregravelling and routinemaintenance of gravel roadscan be very high;

• Unpaved roads generate acontinuous cycle ofdeterioration, which requires

substantial amounts ofreplacement gravel;

• A continuous cycle of gravelroad deterioration resulting in loss of asset value and thecreation of an increasingbacklog;

Technology issues

• Imported motorised gradersare the traditional equipmentfor grading and gravelling orregravelling operations. Thisnot only requiresconsiderable financialinvestment in a high-costfinance environment but alsoraises very serious problemsof ownership and operation of relatively sophisticatedequipment. The net result isoften operational, supportand technical problems, aswell as a local financingburden;

• Very often, spot improvement gravelling may be theoptimum solution forunpaved road maintenance.However, because selectivegravelling in practice isdifficult to achieve, thisresults in wastage of finiteresources;

42

Sustainable provision oflow-volume sealed roads

MI Pinard PAK GreeningInfraAfrica Consultants TRL Ltd

Extract from CAPSA‘04 paper:

• The technology of usinggraders for regravellingpurposes is not sustainable in a number of countries whereit would be preferable toemploy alternative methodsof maintaining unpaved roads involving local communitiesto a greater extent andutilising using local resourcesand management moreextensively.

Social/environmental issues

• There is a continuousdemand for the use of anon-renewable, naturalresource, which is beingseriously depleted in manycountries. As a result, hauldistances and costs arecontinually increasing whileland take is continuing at analarming rate. Moreover,borrow-pit rehabilitation can

be a costly exercise that isoften neglected;

• Dust generation in dryweather causes adverseimpacts in terms of being ahealth hazard forcommunities living adjacentto the road as well as causing pedestrian, animal andvehicle safety problemsrelated to visibility andovertaking movements. Inaddition, dust emissionscause damage to crops andnatural habitats;

• Gravel roads are oftenslippery and dangerous in

wet weather, especially insteep terrain, causing accessproblems for communities.They are also susceptible toerosion causing silting ofdrains and watercourses.

New approaches

Examples of appropriate planningtechniques include the IntegratedRural Accessibility Planningdeveloped by the InternationalLabour Organisation (ILO, 1997),which integrates the mobilityneeds of rural households, thesiting of essential social andeconomic services and theprovision of appropriate transportinfrastructure. In addition, theSustainable Rural Livelihoodsapproach is useful in identifyingthe ways in which any particularinvestment intervention willimpact, benefit or disbenefit thelocal community.

Most of the older models used inthe road appraisal process rely onbenefits arising from reducedmotorised road user costs.

However, many of the benefitsarising from the provision of LVRsare of a social rather thaneconomic nature and thebeneficiaries also includenon-motorised traffic andpedestrians — factors that aretypically not captured inconventional cost-benefit analyses models.

43

In some circumstances bitumen sealing of gravel roads isjustified at traffic levels below 100 vehicles per day.

This makes traditional methods ofeconomic appraisal generallyinappropriate for the appraisal ofLVRs. However, developments intechnology, research andknowledge have created a newplatform for a more rational andup-to-date approach to theeconomics of rural road provision.Improved appraisal methods areincreasingly able to capture thesocial benefits or disbenefitsarising from the provision orabsence of adequate roadinfrastructure which should beincluded in any economicevaluation of rural road projects.

One of the most important outputs of research of the last few years is that in some circumstancesbitumen sealing of gravel roads iseconomically justified at trafficlevels below 100 vehicles per day.

Design: Environmental effectstend to determine theperformance of LVRs. Such effects are quite complex and almost nopavement design methods inregular use cater adequately forthis. From recent research workcarried out in the southern Africaregion the following issues werefound to be the most important for the design of LVRs:

• Selection criteria for roadbase materials;

• Sub-grade strength or design class;

• Crown height above drainlevel;

• Sealed surface design,including the sealing of roadshoulders;

• Geo-climatic zone; • Traffic .

Materials: Materials make up70% of the cost of a typical ruralroad. However, until relativelyrecently many of the designcriteria have reflected specifi-cations which often preclude theuse of many local materialsbecause such materials do notmeet these standards. However,research work carried out in thesouthern African region has shown that many natural gravels haveperformed well as pavementmaterials and considerable usecan therefore be made of themonce appropriate specificationshave been developed fromsuitable research studies.

Surfacing: The challenge is to fitthe materials available to anappropriate seal type rather thanvice versa in the most cost-effective and sustainable manner.For example, where traditionalquality, single sized aggregatewith a relatively high crushing isnot available for use in a ChipSeal, relatively low strength,graded aggregate can besuccessfully used in an Otta Seal.

Geometric Design: Moreappropriate standards are required that are more flexible andresponsive to local conditions. This includes, for example, using a‘design by eye’ approach where no formal alignment calculations aremade and where engineeringjudgment and simple surveys canbe used to define the alignmentand identify where spotimprovements are necessary. Inthis way maximum use can bemade of the existing formationthereby reducing the amount ofadditional earthworks.

44

Road Safety: Traffic surveys,which form the basis of highwayimprovement schemes, rarelyinclude counts of slow-movingtraffic or pedestrians, leading tolarge numbers of accidents,typically 30 to 50 times higher per capita than in developedcountries.

Construction

Compaction: In many designmanuals, the levels of compactionor density to be achieved duringconstruction are defined as aproportion of the maximum drydensity that can be obtained in astandard laboratory test. However, with many road-building materialsand the use of modern plant,higher densities can be achievedwith relatively little additionalcompaction effort. Thus,‘compaction to refusal’ with the

heaviest plant available will oftenprovide a substantial benefit interms of increased pavementstiffness and potentially longerpavement life.

In many circumstancesconsiderable long-term benefitscan be achieved using thesemethods for a relatively smalladditional cost duringconstruction.

Labour-based methods: Inmany countries in the region there is a trend to devolve theresponsibility for rural roads todistrict councils. As a result, many

types of council are nowresponsible for relatively smallnetworks containing few surfacedroads. In these circumstances, the maintenance of these roads (andthe construction of relatively short sections of new road) can becarried out more cost effectivelyusing labour-based methods andappropriate types of plant andequipment that are suited tosmall-scale contractors (Sabita,1995).

Unfortunately, a negativeperception still persists in somecountries that labour-basedmethods are slow, costly andsub-standard. This is not the case; labour-based technology is astructured method of providing ormaintaining infrastructure to aspecified standard whilstoptimising the use of labour under fair working conditions. The use of

labour is supplemented withappropriate equipment wherenecessary for reasons of quality or cost.

Overload control: Traditional,government-driven, approaches to overload control have generallybeen ineffective and suffer from anumber of short-comings.

New, radically different andpromising approaches areemerging in a number of countries which are worthy of consideration(SATCC, 1999). They include:operation which places the onuson overload control on transport

45

Savings of $1.8-billion can be achieved in low volume roadconstruction in the SADC region over 6the next 20 years

operators and freight forwarders;decriminalisation of offences foroverloading by imposing aneconomically-based overloadingfee, and outsourcing ofweighbridge operations to theprivate sector.

Sustainability

It has now become increasinglyapparent in most developingcountries that sustainability mustbecome the basis of a moredemanding policy for the provision of LVRs. Some of the newparadigms include:

Approach: New, approaches must be pursued which satisfy theseven key dimensions, namely -political, social, institutional,technical, economic, financial andenvironmental.

Funding

Alternative financing mechanisms,such as the establishment ofdedicated road funds, coupled with institutional reforms designed tobring private sector skills into theroad sector, have been underwayin many countries during the pastfew years and considerableprogress is being made. Withinthis changing environment it isapparent that the perceived risk of

adopting more innovativesolutions in the provision oflow-volume roads is considerablyless and the climate is morefavourable for greater

implementation; it is for thesereasons that the production of theguideline at this time is opportune.

Environmental sustainability:The environment has often beenregarded as the price to be paidfor development. This has oftenresulted in solutions that areenvironmentally unsustainable. Inmany countries, it is nowabundantly clear that the time has come to provide more sustainablesolutions to LVRs by sealing them, where viable, at an affordablecost. This will require a morecreative approach than hitherto inthe use of local materials.

Research findings

The benefits of successful research can be very large indeed. Suchresearch has shown, for example,

that a revised approach toeconomic appraisal, moreappropriate geometric andpavement design standards, better use of locally available materialsfor the road pavement layers andsurfacing, innovative constructionmethods and greater local andprivate sector participation inmaintenance are just some of theareas where large savings in costs and increases in efficiency can bemade.

Technology transfer

The “local” content in both theconsulting and contractingcomponent of road projects

46

The environment has often been regarded as the price to be paidfor development

(especially sealed roads) in someSADC countries is often very small or at such a level that there arevirtually no opportunities for localpractitioners to influence eitherthe design or the constructionmethodology. In thesecircumstances, technology transfer in either direction is stifled and the long-term goal of sustainabilitythrough technology transfer, about which so much is spoken, isunlikely to be achieved. It is conservatively estimated thatsavings of between US$1 - 1.8billion (authors’ estimate) can beachieved in low-volume road

construction in the SADC regionover the next 20 years by theimplementation of existingknowledge.

Summary

The message is for the engineer to be more flexible in his approach to low-volume roads and to moveaway from the rigidity of designmanuals. It can now be shown tobe justifiable to provide a sealed(or bituminous surfaced) roadrather than a gravel road at traffic levels that are very much lowerthan hitherto thought.

47

This paper is a continuation of previous research intothe state of tertiary

education in pavementengineering in South Africa,with an extension to includenot only asphalt technologybut pavement education.

The authors stress that it isimperative that a finger remainson the pulse of pavementengineering education in SouthAfrica, so that the quality andsupply of engineers, technologistsand technicians can be reconciledwith the needs of industry.

A survey undertaken in 2001 and2002 included a review of thefollowing:

• Matriculation intake;• Students specialising in

pavement engineering;• Lecturer-student contact;• Time spent in laboratories;• Lecturer qualifications;• Physical resources;• Current trends.

Matriculation intake:

The percentage of matriculantswith a C Symbol or higher (aminimum requirement foruniversity entrants) was 22% forscience and 29% for mathematicsin 2000 (of the 4% of learnerswho registered for these subjects), a percentage value that hasremained constant for at least 4years. It is apparent that the trend means that the feeder-group forscience and technology isshrinking in South Africa.

The overall decline takes placeeven before the competition foreligible learners into CivilEngineering begins. Thiscompetition takes the form of

attractive “high tech” streamssuch as Information Technologyand “high prospect streams” suchas Business and ActuarialSciences, as well as fellowengineering disciplines.

Contrary to the gloomy forecastsof the potential feeder-group into

48

The state of tertiary educationin pavement engineering insouth africa

LR Sampson KJ JenkinsAsphalt Academy University of Stellenbosch

It is imperative that the quality and supply of technicians,engineers and technologists be reconciled with the needs ofindustry

Extract from CAPSA‘04 paper:

civil engineering, however, theactual student records ofundergraduate pavementengineering reflect a stable intake. Although not part of the 2002study, the most recent figuresactually obtained show that the2004 intake into pavementengineering in South Africaexperienced an upsurge after apoor 2003 intake.

Minimal variation

The percentage of civil engineering students specialising in pavementengineering at post-graduate level is between 15 and 20%, showingthat the actual variation inpostgraduate student numbers isminimal. And the fact remains that if all of the under-graduate (UG)and post-graduate (PG) studentswere to remain in South Africa and practise engineering, the studentnumbers would probably beadequate. However, the HSRCemigration survey (Horak, 2002)shows that an alarming figure ofsome 24% of civil engineers planto move abroad. Naturally, thethroughputs of universities andtechnikons cannot keep pace withsuch demands.

Lecturer-student contact

The amount of time available totechnikon lecturers to acquaintthemselves with the latestdevelopments in the field or toparticipate in research, issignificantly lower than foruniversity lecturers. This is due tothe relatively higher studentnumbers at the technikons. Theuniversity responsibilities, bycontrast, have more of a focus on

lecturer research and publication,and supervision of studentresearch.

Over ten years, one trend thatappears to be emerging is thespread of student-lecturer contacthours at different institutions,which has gone from consistent tobecoming more erratic. This would apply to both undergraduate andpostgraduate levels.

The laboratory hours continue todominate at the technikons, which is consistent with the philosophyof application of technology taught at these institutions. The use oflecture notes and referencematerial as a PG teaching medium is 40% higher at universities thantechnikons, according to the 2002survey. At the same time, thenumber of contact hours forpostgraduate classes in pavementengineering has increasedsomewhat at universities over thepast 10 years, particularly thosewith specialist staff who promotethis specialisation.

Lecturer qualifications

The numbers of suitably qualifiedlecturing and laboratory staff wasfound to be adequate. The totallecturing contingent in pavementengineering in South Africa hasdecreased by one in theuniversities and one at thetechnikons, in total. There has not been any dramatic change in thedistribution of the lecturers.

In addition to the numbers oflecturing staff, the qualifications of the lecturers has remainedacceptable according to the

49

survey. University staff inpavement engineering generallyhave post-degree qualifications,while technikon staff have firstdegree or post-diplomaqualifications, and in some casespost-degree qualifications. (seeFigure 15).

Physical resources

Libraries: There are two issuesthat raise concerns. Firstly, theresources in the libraries oftechnikons are hopelesslyinadequate, with more than half of the technikons having access toless than 25 volumes on pavement engineering in their libraries. Thesecond issue is probably of greater concern, and that is thedecreasing availability ofliterature. The number of volumeshas definitely declined in the pastten years. It is unclear whetherthis is a result of inaccuratereporting, poorer librarymanagement or loss of resources,

but it occurs contrary to anexpansion of the extent of thesubject resources i.e. from asphalt technology volumes to pavementengineering volumes.

Laboratories: The laboratoryfacilities that are available to

pavement engineering educationhave not changed much in thepast decade. Of the institutionsproviding pavement engineeringeducation, 86% have facilities forgranular, bitumen, asphalt andconcrete testing. However, 36% of the institutions do not have access to non-standard testing facilitiesfor research testing. For thisreason, some 85% of theinstitutions indicated that theywould like to expand their testingcapacity, including tests such asfatigue testing, bitumen rheologyand asphalt testing. There is alsoan interest in bolstering laboratory personnel to carry out the testing.

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Higher Diploma

BTech or MTechBEng or BScEng

Post-degree

Institution

0

1

22.5

3.53

4.54

Figure 15: Lecturer numbers and qualifications for under-graduate pavement engineering

Critical trends

The results of the survey indicatethat during the past ten years,tertiary education in pavementengineering in South Africa hascontinued to maintain a steadyoutput of engineers andtechnicians, with sufficientlecturing staff to provide theeducation. However, certaincritical trends have been noted inthe 2002 survey that requirespecial attention, namely:

• The number of tertiaryinstitutions offering ageneralised background topavement engineering atundergraduate level has been rationalised;

• There has been a slightoverall decline in the numberof specialist pavementengineering staff at tertiaryinstitutions. Within theindustry there is a perception of migration of somepavement specialists fromacademia to positions withinindustry for financial andwork-environment reasons;

• Reduction in library resources in pavement engineering that are available to students;

• Poor quality of specialistlaboratory equipment ishindering research initiativesand the attraction of goodpost-graduate students intopavement engineering.

The “Professor workshops” wereimplemented by the Sabita Chairat the University of Stellenbosch in 1998 to create an efficientknowledge transfer environmentwith updates in “state of the art”

pavement technology, withoutlecturers having to attend manyinternational conferences. Thisenabled the latest technology tobe processed into an educationalcontext and integrated into course material. It is now a specificstrategic objective of the AsphaltAcademy to develop andreconvene a course or workshopof this nature.

Conclusions

The survey conducted in 2002 has highlighted some importantdevelopments in pavementengineering in South Africa overthe past decade. When juxtaposed against the state of the industryten years prior, certainconclusions may be drawn:

• Where the success ofoverseas universities centredaround at least 60 final yearstudents with an equivalentacademic staff of at least 25,the South African scenario isgenerally considerably less.Most universities andtechnikons have between 30and 50 students in final yearundergraduate classes;

• Despite the intake ofundergraduate civilengineering students in South Africa being satisfactory, thefact that pavementengineering is not offered atB.Tech level at technikons,but is included in urbanengineering andtransportation engineeringqualifications, militatesagainst the road sectorattracting newly qualifiedgraduates and in particular

51

top quality students. TheAsphalt Academy is currentlyinvestigating thedevelopment of a blockcourse in flexible pavementengineering for presentationto newly qualified civilengineers and techniciansentering the roads industry to address this issue for thosewishing to specialise inpavement engineering;

• Specialised laboratoryequipment for pavementengineering researchpurposes is limited to a fewinstitutions. In general, theequipment for specialisedresearch at tertiaryinstitutions is seen as poorand is also perceived as an

added problem in attractingstudents to specialise inpavement engineering;

• Certain recommendationsemanating from the 1992survey were addressed in the following decade. Inparticular, the establishmentof the Asphalt Academy andthe SANRAL Chair atStellenbosch University, have amongst others, assisted inachieving these goals.Several issues remainunaddressed, however, suchas scholarships, resources(laboratory and libraryfacilities) and lecturing staff.

These still require attention.

52

A guiding principle in theprovision of roads should be that the engineering

standard of the road bedetermined by the type andvolume of traffic that isexpected to use that road.

Infrastructure that is “over-designed” is not only moreexpensive than necessary to build, but is also more costly tomaintain. Engineers, many ofwhom have very little experiencewith or confidence in the design of low-trafficked infrastructure, havea tendency to promote standardsthat are too high for low volumetransport infrastructure, and arereluctant to depart from the norms set for higher level roads.

Infrastructure planning is alsoproblematic in rural areas,particularly in the evaluation ofbenefits — which in rural areastend to be social rather thaneconomic. A primary problem is inthe estimation of traffic volumes,which in the initial stages may bevery low. Secondly, because of the high occurrence of non-motorisedtransport (carts, donkeys,pedestrians etc), there areproblems with the evaluation ofbenefits. Thirdly, the

infra-marginal nature of theimpact on basic access to someactivities — for example themarketing of agricultural produceor crafts becomes possible, orattendance at a school or clinicbecomes possible, because of theproject, and would be impossiblewithout the project — means thatthese impacts appear lessconvincing than the changesstimulated by improvements toexisting networks. And finally, thecosts of detailed economicappraisal of individual smallprojects tend to make less sensethan for undertakings in which the project appraisal costs are asmaller proportion of the totalproject costs.

The whole principle of Opportunity Value Assessment (OVA) is basedon the concept that roads are only really valuable to the extent thatthey add value to other activitieslinked to roads. It thus followsthat road (or transport policy)should be part of a holisticdevelopment strategy thatdetermines the priorities for roadinvestment, in the context ofeconomic and social objectivesand environmental, funding andinstitutional constraints.

53

Infrastructure financingand provisionS Muradzikwa University of Cape Town

Roads are only really valuable to the extent that they add valueto other activities linked to roads

Extract from CAPSA‘04 paper:

Inter-departmental integrateddevelopment planning (of whichroads are just one ‘cross-cutting’component) need to maximise the economies to be gained fromharnessing the linkages of variousroads, plus other projects, intoholistic development programmes.In a nutshell, road investment willonly be effective if carried out inthe context of an acceptabledevelopment strategy.

Research Agenda

The results of studies carried outon rural road infrastructure in theIngwavuma district ofKwaZulu-Natal underlines thevalue of appraisal of programmesrather than projects, and forconcentrating on costeffectiveness of specificinterventions.

The motivation for developing aprioritisation tool, and animproved process for translatingpriorities into coherent networksof linked plans, is to introducesome form of rational decision-making into a local planningprocess, and to relate this toprinciples of economic analysisand the desire for social/humandevelopment.

Research has shown that animportant component of thisplanning process is the involve-ment of communities in projectprioritisation, which numerouscase studies have shown togenerate some form of “owner-

ship” as key to successful ruralinfrastructure (including roads)interventions.

Challenge

The real challenge lies in how tosystematically model therelationship between ruralinfrastructure and the variousdependent variables, such thatthe model is a fairly accuratepredictor of capital-deepening andthe wider socio-economic benefitsof rural infrastructure provision.Such a prioritisation tool wouldtypically be a locally adapted(calibrated) version of multi-criteria analysis.

Roads derive much of their valuefrom their contributions to thevalues of other assets, such asschools, hospitals and business

concentrations that they makepossible, and then these assets inturn feed wealth-creatingproductivity. It must be noted that it is far easier to build such assetsefficiently from already-existingbases than it is from conditions ofacute capital deprivation. To putthis into perspective, consider thefollowing example:

Take the case of a provincial roadagency debating whether to build/upgrade a road that services asmall concentration of touristfacilities, or one that will enablerural farmers to drive, instead ofwalk their farm produce to a mainhighway.

54

Rural areas, home to more than 50% of the population, accountfor just less than 12% of all road infrastructure

The short term capital-assetpotential of the farmers is so small on the margin that astandard cost benefit analysis(CBA) instrument will neverindicate in favour of their roadsunless your plug-on model isspecifically designed to swamp the efficiencies the general model issupposed to measure. However,this implies that your ad hocplug-on is doing all the work, andyour model isn’t doing any!

By no means is it being suggestedthat one should take it for granted that rural farmers have thepriority call on infrastructurefunding just because they arepoorer. Rather, what is beingsuggested is that the relativelyhigh inequality in South Africa(measured by comparison of GINIcoefficients across a basket ofcountries) significantly undermines attempts to make infrastructure

prioritisation systematic andreliable.

With this in mind it is perhapsunderstandable that ruralsettlement areas, home to morethan 50% of the South Africanpopulation, account for just lessthan 12% of all roadinfrastructure. It also highlightsthe fact that the importance of the road network in deliveringnational, social and economicobjectives is rarely matched bythe performance of government in providing infrastructure of theappropriate quality and quantity.

A vital guiding principle ofinfrastructure improvements isthat they should be sustainable,and any chosen project shouldonly be carried out up to the limitof what can be maintained in thefuture.

55

Colas 1 ad here

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57

59

Safe and

efficient

delivery

’

This paper reports on thechange in the propertiesof bitumen change during

bulk storage, transport, andstorage on site. Using datafrom two South African andAustralian laboratory studiesinto ageing of bitumen, a lackof correlation between bulksample ageing and smallsample ageing is found. It isfound that changes inproperties from refinery topavement also come frommicro-contamination fromnormal work practices.

A South African study intobitumen ageing and the

in-tankage changes in the qualityof bulk bitumen was done in 2002(Coe, 2003). Four samples ofabout four litres each of SouthAfrican 80/100 bitumen weredrawn from large bulk storage atCalref refinery and distributed toparticipating laboratories. Theywere instructed to store thesamples in their ovens at atemperature of 1600C or as closeto this temperature as possible.On a weekly basis, a sample wasdrawn from the four-litre tin andtested for penetration andsoftening point. Testing wascontinued until sample depletion,which took approximately sixweeks.

61

Monitoring bitumen qualityfrom refinery to pavement

SJ Emery J O’Connell L WhiteKubu (Pty) Ltd Sasol Fuels Research Liquid Laboratories

Table 1 Ageing of 80/100 small samples at 1600C (penetration @ 250C, 0.1mm)

Days ageing Laboratoryrefinery

Laboratory S Laboratory M Laboratory C

1 82 80 79 67

3 81 84 74 65

5 75 85 70 60

8 76 83 65 57

10 80 59 51

12 53 54

15 78 46 48 41

17 77 45 45 40

19 73 45 41 39

22 76 39 36

24 73 36 34

26 69 32 31

Extract from CAPSA‘04 paper:

The results for penetration areshown in Table 1, and showsignificant variations with time asexpected, but also quite avariation between laboratories.While all showed a trend todecreasing penetration uponageing, the extent varied. The paper reports that the changein viscosity when ageing in bulkstorage was found to be

considerably different from that ofsmall samples, even if properlysealed and the same bitumensource. Figure 2 shows the change in viscosity of bulk storage (meanof the three tanks in Table 3) andsmall samples (sealed tins of Table 2). It shows how any study on

bitumen ageing can beconfounded by the ageing effect of small samples, as previouslysuspected. It also indicates thatthe safe storage period forbitumen at elevated temperaturesis longer than that codified.However periodic retesting ofbitumen stored at elevatedtemperatures is warranted in viewof the changes in bitumen

properties over time.(Refer Table 9.)

The authors conclude that:

• Change in viscosity whenageing in bulk storage wasfound to occur, but to be

62

Figure 2: Bitumen ageing in hot storage (small tins 1630C, bulk 120-1650C)

Tank Size Maximum storage period betweenbitumen re-testing

Greater than 250 tonnes 45 days100 tonnes 30 days

25 tonnes 15 days

Table 9: Proposed bitumen re-testing requirements for bitumen stored at120-1650C

Small sealed sample

Bulk storage

TIME (days

0

0

5 10 15 20 25

250

500

750

1000

1250

1500

different from that found inageing small samples in thelaboratory;

• The ageing index (ratio of“viscosity aged” to “viscosityunaged”) of bitumen storedat elevated temperatures was found to increase by 0.0034per day in bulk storage,0.0098 per day for bulk seatransport, 0.0137 per day for

road transport, and 0.0168per day in site storage;

• Micro-contamination occursas a result of normalpractices at the loading pointof the refinery or bulkstorage, but downstream ofthe loading arm. It occurs inthe road vehicle due tocurrent design and operatingpractices.

63

Time Control sample Sealed tins

Visc60 Visc135 Pen25 Visc60 Visc135 Pen25

0 167 0.510 72 167 0.510 726 hours 176 0.370 62 182 0.560 57

24 hours 189 0.510 55 172 0.410 48

3 days 226 0.410 49 189 0.448 45

8 days 343 0.500 23 279 0.442 28

15 days 762 0.633 12 453 0.558 17

19 days 958 0.883 9 563 0.660 13

26 days 1302 1.250 8 1260 0.920 9

Table 2: Ageing of Class 170 small samples at 1630C

Property Time in storage (days)

0 1 4 26 39 59 Tank 1: 2650 tonne capacity, 120

0C

Viscosity @ 600C Pa.s 150 149 150 168 171 173

Viscosity @ 1350C Pa.s 0.36 0.45

Penetration @ 250C,

0.1mm73 66 62 64 54 52

Tank 2: 1 400 tonne capacity, 1650CViscosity @ 600C Pa.s 141 156 170 170 175

Viscosity @ 1350C Pa.s 0.34 0.36

Penetration @ 250C,0.1mm

75 71 57 54 52

Tank 3: 1 650 tonne capacity, 1400C

Viscosity @ 600C Pa.s 145 153 170 175

Viscosity @ 1350C Pa.s 0.35 0.39

Penetration @ 250C,0.1mm

75 68 60 54

Table 3: Change in a Class 170 bitumen properties in bulk storage

The policy in The Nether-lands is to lay porousasphalt (PA) 0/16 as a

surface wearing course onmotorways especially becauseof the good noise reductionproperties.

At this moment 65% of the motor- way wearing courses consist of PAand the goal is to approach 100%in 2010. The mean service life ofPA is 12 years on the right laneand 16 years on the fast lane[Verra, 2003]. The end of servicelife of PA is mainly caused by anexcessive loss of stones from thesurface called ravelling.

For environmental reasons the policy is that all asphalt must be reused atthe end of service life. Until nowmilled PA is reused in asphalt mixeslike base course layers and denseasphalt concrete. It is notallowed to use RAP in PA, becausePA is a critical mix.

Another policy in The Netherlandsis to try to reduce the energyconsumption as much as possible.

This applies also for the asphaltproduction. The same counts forthe decrease of emissions duringmanufacturing and laying. Allthese goals could be possiblyreached using the half-warmfoamed bitumen treatmentprocess.

Therefore this project tried tocombine these three policy goals:reuse PA RAP in new PA (noisereduction) with lower energy. To investigate if this is possible, alaboratory project was carried outto determine if PA RAP could bereused in PA with the half-warm process. Of course the durability

and performance of half-warmfoam (HWF) PA mixes must beclose or equal to hot PA.

Results of experiments

Ageing of foamed bitumen:

Tables are provided from which itcan be seen that foamed bitumenrecovered from HWF PA specimens has a lower penetration (12*10 -1

64

Experiences with half-warmfoamed bitumen treatmentprocess in The NetherlandsJLM Voskuilen S Mangnus MFC van de VenMinistry of Transport Ingenieursbureau Van Kleef Delft UniversityNetherlands Netherlands Netherlands

JBM van Wieringen JNA BolkMinistry of Transport Heijmans InfrastructureNetherlands Netherlands

For environmental reasons the policy is that all asphalt must bereused at the end of service life

Extract from CAPSA‘04 paper:

mm) and a higher softening pointring and ball (2.4°C) thanrecovered bitumen from hot PA, so despite the lower mixingtemperature of 95°C the foamprocess has a higher impact onthe bitumen ageing in comparisonwith the hot process.

Possible causes are the exposureof a larger bitumen surface tooxygen, due to the thin layerthickness of the bitumen bubbles. Table 7 may indicate that the long

circulation time of 2 hours of thebitumen in the foam bitumenapparatus can also make acontribution to extra bitumenageing. From Table 7 it can alsobe concluded that the additive acts like a rejuvenator.

From these limited experiences the ageing process during half- warmspecimen preparation is notdirectly clear, so it is recommen-ded that more detailed attention be paid to the background of ageingduring the half-warm process. GelPermeation Chromatography (GPC) is a useful tool for this purpose.

Composition of mixes

Generally the scatter in mixcomposition was much more thanexpected, despite the 10 kgbatches that were made toprepare specimens.

The scatter in grading of phase 2a1

mixes is greater than the phase 2b2

mixes. The bitumen content of theHWF mixes of phase 2b wasconsistently too high. Obviously it is very difficult to prepare HWF PA

specimens with a low scatter ingrading and close to the desired(foam) bitumen content. Therecould be several reasons for this:

• the PA RAP does not have the assumed homogeneity;

• during the mixing process alot of coarse material iscrushed;

• the dosage of foam bitumenin the Wirtgen apparatusWLB10 is possibly notaccurate enough;

• in the batch mixer alwayssome mortar remains, whichmaybe differs from time totime;

65

Properties (after 2 hours at 1700C) Penetration(10-1mm)

Tr&b (0C)

Eshafoam 100, not foamed, no additive 65 48.6

Eshafoam 100, foamed, no additive 65 48.6

Eshafoam 100, not foamed, with additive 80 45.8

Eshafoam 100, foamed, with additive 80 46

Eshafoam 100, original 81 45.8

Table 7: Properties of foamed and not foamed bitumen with and without additive

1: Initial research on mechanical properties2. Advanced research on durability

• the optimal paddleadjustment changes in time,because the mixer paddleswear.

It is possible the mixer used is not suitable for the production of PAmixes with a sufficient accuracy inmix composition. Sand skeletonmixes like the base coarse layerStone Asphalt Concrete (StAC) are less sensitive for this inaccuracy in comparison with PA. This wasshown by Jenkins, (2000).

Differences between lab andfield

Is water needed?

Because the relation between themechanical properties and theresistance to ravelling is unknown, it is only possible to compare themechanical results with the results of hot PA, hoping that thesemechanical properties have a good relation with the ravellingbehaviour in practice. It is clearthat most results of HWF PA mixes are worse in comparison with hotPA. Maybe the presence of waterin HWF PA mixes is one of thecauses of the disappointingresults.

In the laboratory it is not possibleto prepare HWF PA specimenswithout water, because water isneeded to coat the aggregate andthe PA RAP totally with foamedbitumen (Workshop Schuim-bitumen, 2003).

It is remarkable that in anotherproject it was determined that forthe production of HWF PAcontaining new materials no water

was needed in the asphalt mixplant. Visual inspection revealedthat all aggregates were totallycoated with foamed bitumen.Obviously there is a greatdifference between laboratorymixing and plant mixing, but there must nevertheless be a way toprepare HWF PA specimen in thelaboratory without using water. To investigate if HWF PA mixes are as durable as hot PA it is recommen-ded that the investigation beginwith mechanical properties ofplant-mixed HWF PA mixeswithout water. If this is confirmedone can try to simulate thisprocess in the laboratory.

Black rock principle?

Does the PA RAP with highly agedbitumen act like rock or does theaged bitumen in the PA RAP mixup with freshly added bitumen? Because PA is gap graded (gapbetween 2 an 6 mm), it is a stoneskeleton mix. This stone skeletonis fixed with a binder, in this casethe mortar (mix of sand, filler andbitumen). To determine if themortar of PA RAP has some binder properties, we attempted todetermine the softening point Tr&bof the recovered mortar. It wasamazing that at temperaturesbelow 150°C it was not possible to prepare specimens for thesoftening point Tr&b test (nobonding) and the mortar colourwas not black! At 160°C themortar turns black and at 170°Csome bonding effect was noticed.So the bitumen in the PA RAP wasaged in such a way that no flexible mortar could be created at thesetemperatures. Mixing betweennew and aged bitumen would,

66

especially at 95°C, be very small.Some migration could be possiblein time.

In Phase 1, HWF PA mixes withfoamed bitumen content between2.5 and 4.0% were tested in theITT. Mixes with 3.5% foambitumen gave the best results. Hot PA mixes normally contains 4.5%bitumen, so this is an indicationthat maybe some of the agedbitumen of PA RAP is mixed withthe foamed bitumen.

On the other hand: in a CROWproject Re-use of Asphalt (CROWPublication 179, 2002) it wasdetermined that mixes with anincreasing RAP content have abetter resistance to permanentdeformation than mixes containing only new materials. A possibleexplanation is that mixes with RAP need less bitumen, because nolight bitumen fractions areabsorbed by RAP because RAP isalready “pre-coated” withbitumen.

So the conclusion about PA RAP isthat it neither acts as a black rocknor as a particle coated with

bitumen because there is no totalmixing between aged bitumen and new foamed bitumen. The feelingat the moment is that it approach- es closer to the black rockprinciple. This is illustrated inFigure 4.

In The Netherlands it is commonto re-use up to 50% RAP in basecourse asphalt mixes. To obtainthe required penetration of themix of aged bitumen from the RAP and the added fresh bitumen, theso-called log pen rule is used.With the data of the penetration of aged bitumen from RAP and freshbitumen, and the mass ratio ofaged bitumen from RAP and freshbitumen, the penetration of thebitumen in the mix with RAP maybe calculated as follows:

a log (pen1) + b log(pen2) =(a+b) log pen mix

Where:

a and b are expressed in mass ratio of theaged bitumen of RAP and the freshbitumen respectively (a+b=1)Pen1 = penetration of aged bitumen fromRAPPen2 = penetration of fresh bitumenPen mix = calculated penetration of thebitumen of the mix with RAP

67

100%

0%

Black rock Cold Half Warm Hot

100%

0%

No MuchDegree of interaction

Log pen rule

Figure 4: Interaction between RAP bitumen and fresh bitumen

The log pen rule only applies tohot mixes, assuming that the aged bitumen and fresh bitumenbecome a one-phase system. IfRAP is reused cold, one has tomake do with the black rockprinciple. There will be no mixingof the aged and fresh bitumen atall, which will result in a two-phase system

Conclusions

For lab mixing with the usedlaboratory mixer it is necessary toadd water to coat the aggregatewith foamed bitumen. Becausewater addition is not needed in the

asphalt plant, this means thatthere is a difference between laband field production.Overall the test results show thatthe half warm foam process couldbe an alternative in the nearfuture for hot mixes, but toconfirm this and because of thevarying test results more research work is needed.

Because of some disappointingresults of the functional anddurability tests, no HWF PA mixcould be recommended to apply in a test site under traffic at thismoment.

68

In this paper the impact ofrisk on whole-of-lifecosting is addressed

through a design levelprocedure proposed to assistin maximising the reliability ofthe final selection. It is theissue of risk that provides arevised view, and proceduresare proposed for comparison of alternatives.

The revised whole-of-life costingmethodology presented includesan overview of the issues relatingto comparison of alternatives

covering ownership and fundingissues, as well as a methodologyfor carrying out comparisons. Theprovision of a risk managementprocedure enables specific risksand their consequences to beidentified and quantified. Thisimproves the reliability of theselected alternative. The conceptspresented in this paper can beused by practitioners to provideassistance in comparingalternative pavement designs with the incorporation of ownershipissues.

One of the difficulties in usingcurrent whole-of-life analysisprocedures is that there isfrequently little consideration oflikely construction specifications,construction delivery mechanismsand skill levels or likelymaintenance regimes, all of whichhave a significant influence onpavement performance. Foreffective analysis both thedesigner and the constructor needto be involved, and through theapplication of risk assessmentprocedures, to arrive at a closerconsideration of these issues.

In addition, the risks associatedwith each whole-of-life pavementscenario need careful considera-tion. Risks can be allowed for bythe application of a “designreliability factor”, which is amultiplier for the calculated design traffic. Due to a lack of validationof the performance of existingpavements against design, thisbroad based approach hasattempted to take into account anumber of threats leading to poorperformance such as:

69

Whole of life costing –incorporating ownership issuesand design riskRM Vos GP YoudaleAAPA Consulting Engineer

Improved cooperation on key issues is vital to the achievementof optimum, long-term pavement performance

Extract from CAPSA‘04 paper:

• Uncertainty in estimatingdesign traffic loading;

• Variations in in-situ materials properties as constructed and over the life of the pavement;

• Variations in pavement layerthicknesses;

• Accuracy of the designmethod for various pavement types.

A more rational assessment ofrisk, project reliability and thelikely whole-of-life cost estimationcan be made where these

uncertainties are quantifiable and,to a certain extent, controllable for a particular project. The method-ology proposed is illustrated inFigure 2.

The paper deals with all thesephases and subsets in some detail. In Phase 4 Cost Comparisons itstates that once the present worth of cost (PWOC) of each riskscenario of a pavement designalternative has been determined,these are combined to get a

70

Figure 1: Typical interaction between design, construction and maintenance

Owner

Construction

Maintenance

Design

Owner

Construction

Design

Maintenance

Æ

PWOCA=

[P1 x PWOCA1]+[P2xPWOCA2]+[P3xPWOCA3]+[P4xPWOCA4]+[P neutral x PWOCAneutral]

Where

PWOCAi = Present Worth of Cost for pavement design alternative A with risk profile I

Pi = Probability of risk scenario IPWOCA = The weighted Present Worth of Cost for that pavement

alternative.

71

Utilise a suitable selection and designguide for flexible pavements (National guideline or specification)

Chance that the pavement will outlast the design traffic

For example:

• Under-estimation of designtraffic;

• Non-achievement of materialsdesign parameters;

• Under-thickness of pavementlayers;

• Etc....

• Qualitative risk assessment todetermine likelihood andconsequences;

• Mitigate risks where practical;• Quantify consequences of

uncontrolled risk using suitabledesign analysis procedure;

• Quantify likelihood ofuncontrolled risk.

Whole-of-life cost analysis usingPWOC on a weighted probability basis over a common analysis period.

Apply sensitivity analysis onwhole-of-life costs using appropriatevariable in PWOC calculation.

Perform value judgement assessment based on identified ownership issuesand rank alternatives.

Phase 1PavementSelection

Phase 2Risk

Assessment

Phase 3Performance

Analysis

Phase 4Cost

Comparisons

Phase 5PavementRanking

Identify suitable candidate pavement types required

Choose level of projectreliability

Analyse likely pavementperformance taking risksinto account

Identify and assess riskassociated with eachcandidate pavement type

Mitigate risks whereverpossible

Compare whole-of-lifecosts and proposesuitable pavements

Undertake valuejudgement of ownershipissues and selectpreferred pavementoption

Figure 2: Methodology for comparison of pavements

weighted PWOC for thatpavement type.

The calculation is detailed below.Alternative pavement PWOCs arethen compared to ascertain thelowest PWOC. The PWOCcomparison of alternatives shouldinclude testing for sensitivityagainst the input parameters as

reflected in the comparison inTable 9 of Full Depth Asphalt andComposite Pavements. (AAPA2003).

These results provide input to adecision model, such as theAssessment Matrix in Table 10

below, which incorporates lessquantifiable operational,environmental and social aspectsof the ownership.

Selection of candidatepavements

Candidate pavement types shouldbe chosen by the designer, and

detailed guidance in this regard isavailable from national pavementdesign guides. The desiredreliability is also chosen by thedesigner, and should be considered on a project by project basis afterconsidering ownership issues assuggested in Table 1.

72

Full Depth Asphalt

Scenario 4% 7% 10% Probability1 $65.82 $69.30 $70.56 0.4

2 $68.13 $71.48 $72.21 0.33 $66.47 $69.73 $70.84 0.2

5 $69.28 $72.57 $73.34 0.1

PWOC $66.99 $70.37 $71.39 FDA

Composite PavementScenario 4% 7% 10% Probability1 $77.68 $80.93 $82.02 0.4

2 $82.90 $84.97 $84.23 0.3

4 $80.14 $82.82 $83.42 0.2

6 $84.36 $86.69 $86.79 0.1

PWOC $80.41 $83.10 $83.44 Composite

Table 9 - Example of PWOC values for Full Depth Asphalt & for CompositePavement

The above table is based on an example with the following design inputs:

Subgrade CBR WMAPT 250C Design life 25 years Traffic growth 4%

73

Probable PWOC for each alternate

Sensitivity analysisvariable1

FDA Composite

DesignIssues

Analysis of alternate through design level riskassessment and inclusionof probability toevaluation of includedscenarios. A suitablevariable is chosen in thePWOC analysis to identify the range of outcomes.

Discount rate 4% $66.99 $80.41

Discount rate 7% $70.37 $83.10

Discount rate 10% $71.39 $83.44

Categories Weighting of project2

ValueJudgement3

Weighted value

FDA Composite FDA Composite

Owner- shipIssues

1. Investment & economic strategy

0.7 1.0 0.9 0.7 0.63

2. Planning and development strategy

0.9 0.8 1.0 0.72 0.9

3. Owner risk profile

1.0 0.7 0.7 0.7 0.7

4. Construction & maintenance

0.8 0.9 0.7 0.72 0.56

5. Political, social &environmental

1.0 0.8 0.9 0.8 0.9

Weighted score for each alternative 3.64 3.69

Overall ranking4

FDA Composite

Based on weighted Value Judgement Assessment of relative valueof Ownership Issues and probable PWOC of Design Issues

1 1

Some of the risks identified, which cannot be reduced at the design phase, can then betargeted for closer attention during construction and ongoing maintenance.

Table 10. Assessment matrix for design and ownership issues(Examples of FDA and Composite pavements)

Notes:

1. Suitable variable chosen to identify the range of PWOC possible from the selected alternatives; 2. Weighting for the project based on a scale of 0 to 1 where 0 is Insignificant to the category and 1 is Extremely Important; 3. Value Judgement of the Alternate to the category or detailed ownership Issue based on a scale of 0 to 1 which reflects the impact of that alternative. 1 would indicate a very positive impact an d a 0 value indicates a very negative impact. Further subdivision of each category is used to highlight divergent issues or those significant to the range of alternatives proposed; 4. Overall ranking of the Alternate should identify if there is only one “best choice” i.e. lowest PWOC and highest Weighted Value. In this case the PWOC of FDA is lower but Composite Weighted Value is marginally higher. Best approach would be to test the PWOC on actual tender values.

CONCLUSION

The authors conclude that theincorporation of a risk assessmentprocedure in designer levelwhole-of-life costing analysisoffers a robust input into theselection of pavementalternatives. It provides theopportunity for designers toidentify, assess, and in some

cases reduce, the site-specificrisks associated with anyparticular job.

Some of the risks identified, which cannot be reduced at the designphase, can then be targeted forcloser attention duringconstruction and ongoingmaintenance.

74

Road Class Suggested project reliability(%)

Freeway 90 - 97.5

Highway: Lane AADT > 2000 87.5 - 97.5

Highway: Lane AADT < 2000 85 - 95

Main Road: Lane AADT > 500 85 - 95

Main Road: Lane AADT < 500 80 - 90

Table 1: Suggested project reliability levels (from ARPG 2001)

Bitumen and coal tar areoften confused. Bitumenis manufactured from

crude oil by distillation undervacuum, whereas coal tar isderived from coal bydestructive distillation at hightemperatures.

Bitumen and coal tar are howeverextremely different, in terms ofphysical characteristics, chemicalcomposition and the nature anddegree of hazard presented tousers. In particular coal tarscontain significantly higher levelsof polycyclic aromatics (PCAs) and many coal tars are considered tobe carcinogenic, whereasbitumens are not.

Increased interest in the potentialof bitumen emissions to affecthealth was primarily driven by thefact that both bitumen and it’semissions at elevatedtemperature, can contain smallamounts of polycyclic aromaticcompounds, some of which arecarcinogenic. Whilst it is believedthat the carcinogenic risk fromexposure is extremely low, thereremains some uncertainty. Further health studies are underway toresolve remaining issues andimproved working practicesadopted to reduce the potential for

exposure during work with hotbitumen.

Ongoing Health EffectsResearch

1. Toxicological Studies

To evaluate the carcinogenichazard potential of emissions from hot bitumen, the German Bitumen Producers Association (ARBIT) has commissioned a long-terminhalation study in rats. The material being tested is acondensate, collected from theheadspace of a bitumen storagetank, maintained at a temperature of 1750C.

The liquid condensate and thelaboratory-generated atmospherehave been validated againstexposure samples collected fromthe breathing zone of workersduring typical ‘field’ pavingoperations. The composition, andphysico-chemical properties of the condensate/exposure atmosphere, match closely ‘field’ exposuremeasurements.

The study involves the exposure of rats to a laboratory-generatedatmosphere of bitumen aerosoland vapour at levels up to100mg/m 3 (THC). The maximum

75

Bitumen occupational health –update on recent activities

T Riley BP Product Stewardship Group

Extract from CAPSA‘04 paper:

exposure concentration chosen is10 times the current OEL inGermany, and was based on themaximum level likely to betolerated by the rats over a 2-year exposure period. The study isscheduled for completion during2005.

To provide additional informationto assist in evaluating the resultsof the ARBIT commissioned study, Eurobitume is sponsoring a seriesof additional investigations. Thiswork is running in parallel to theARBIT study and is beingundertaken in the samelaboratory. These investigationsare utilising ‘state-of-the-art’scientific techniques, and willprovide vital scientific information

on the mechanisms of anytoxicological response seen in themain study.

2. Human Studies

To address the question whetheroccupational exposure to bitumenis associated with any increasedrisk of developing cancer,Eurobitume, EAPA and CONCAWEasked IARC (the InternationalAgency for Research on Cancer —a division of the World HealthOrganisation) to carry out anepidemiological study of workersin the asphalt industry. Followinga technical feasibility study, IARChas completed a major ‘cohort’mortality study of Europeanasphalt workers. (Boffeta et al2003)

The study investigated the causesof mortality in over 80,000workers and compared theincidence of disease, withparticular emphasis on cancer, in~ 30,000 workers exposed tobitumen emissions relative to both the general population andconstruction industry workers who had not been exposed to bitumenemissions.

The cohort of workers was drawnfrom seven European and onenon-European countries, andexposure assessments weredocumented for bitumen fume,coal tar, Poly AromaticHydrocarbons (PAHs), organicvapour, diesel exhaust, asbestosand silica.

Results showed a not unexpectedclear ‘healthy worker effect’ withthe overall incidence of mortalityfrom all causes being lower thanthe general population. There washowever a slight, but statisticallysignificant, increase in the overallincidence of lung cancer in asphalt workers but the incidence was notconsistent across countries.

The study was unable to drawconclusions however on thepresence or absence of a cause-effect link between the incidenceof lung cancer and exposure toemissions from bitumen. The main reason for this was the lack ofadequate data on worker exposure to other factors that may have contributed to the slightly increased incidence of lung cancer,

76

Any risk to health from exposure to emissions from hotbitumen is extremely small

such as smoking habits andexposure to coal tar. The data doindicate however that any risk tohealth from exposure to emissions from hot bitumen is very small.

In view of the inconclusive resultsfrom the cohort study, IARCrecommended undertaking afurther investigation into thecauses of the slight increase inincidence of lung cancer.

The proposed ‘nested case control’ study will investigate in moredetail each case of lung cancerand endeavour to obtain moredetailed information on potentialoccupational and non-occupational causative factors.

Particular emphasis will be placedon smoking habits and coal tarexposure. This study is to befunded by an industry consortiumand is currently in the finalplanning stage. It is anticipatedthat the study will start during2004.

Conclusion

Bitumen does not present anyhealth or environmental hazardsat ambient temperature andresults of existing studies onbitumen emissions arising fromheating have so far shown that the risk of health effects in exposedworkers is extremely low. Bitumen remains a focus for health effectsresearch however, primarily dueto the presence of very smallamounts of polycyclic aromatichydrocarbons in the product anduncertainty about the associatedhealth risks from exposure toemissions from hot bitumen.

The bitumen industry is workingclosely with regulatory andscientific bodies to resolveremaining questions. Furtherstudies are in progress, employing state of the art techniques, whichshould resolve finally the questionwhether exposure to bitumenemissions presents a cancer risk.In addition to the health effectsresearch discussed, industry hasbeen active in promotingstrategies to reduce workerexposure to emissions from hotbitumen work.

77

This paper analyses theprerequisites associatedwith the adoption of

performance-basedspecifications, the need forcontinuous research andstandardisation, innovationpolicy, adaptation ofprocurement laws and aboveall a new state of mind.

A close cooperation between thepublic and private sectors canboost the innovation process. InFrance, developing and fosteringinnovation in conjunction withcontracting companies has alwaysbeen one of the main-springs ofthe French Road Directorate’s

action. Two systems are described below: the Road InnovationCharter and the TechnicalCertificates.

1. The Road Innovation Charter

The Road Innovation Charter is astructured procedure set up by the Directorate of Roads to encouragethe process of maturing and

disseminating major innovations in the field of road engineering.

Coping with a sharp increase inthe heavy trucks traffic, improving travel in urban areas, providingconditions of safety and comfort to meet user requirement, preserving the living environment of frontageresidents and saving materialsresources are examples of thechallenges that have to be met.

This means prioritising specifictechnical choices, adaptingprojects, discovering and testinginnovations, while also makingcontinual progress in the quality of engineering structures.

The development of a newtechnique requires not only priorstudies and phased site testingbut, above all, a rigorous workand monitoring programme. Thisprocess may prove to be lengthyand costly. The innovation itselfmay entail risks for the Employerof the Contractor. It is thereforeessential to set up a well-structured procedure aimed atachieving maximum efficiency.

78

European experiences withperformance guarantee and/orproduct guarantee systems

M Démarre É le BouteillerColas SA (Pty) Ltd Colas SA (Pty) Ltd

The development of a new technique requires … a rigorous workand monitoring programme

Extract from CAPSA‘04 paper:

The Directorate of Roadsdetermines the themes itconsiders most important for thenational network, on which itrequires an innovation effort to bemade. Any contractor can propose a project for one of these themes.To this end, it draws up a package that describes the project, detailsmethod of use, financial issuesand gives the results of priorstudies and tests, together withthe references.

The Charter comprises fourstages:

• Prospective sample sections:short sections to give an idea of the innovation in concreteterms, as far upstream aspossible;

• Experimental samplesections: sections of limitedlength enabling theinnovation to be validatedafter specific laboratorystudies;

• Technical demonstrationjobsites: sections ofsignificant length enablingthe full-scale innovation andits implementation to betechnically validated, afterfavourable conclusions in thepreceding stages;

• Economic demonstration

jobsites: sections ofsignificant length awardedonce the previous stage hasachieved successful results,after a competition enabling

the innovation to beeconomically validated.

The system has proven itsefficiency: by the end of 2000, 75protocols had been signed sincethe beginning of the process, and175 sites had been constructedand evaluated. Only ten of themfailed.

The system has been extended tothe concessionaire motorwaynetwork. For 2004, the themesthat have been selected are:

• Cleanliness of the tack coats;• Processing specific spots as

far as texture and skidresistance are concerned;

• Recycling drainage asphalt at the end of their service life;

• Warm asphalt mixes formaintenance.

2. The Technical Certificates

Beside the Road InnovationCharter, a system has beenestablished to support thedevelopment andcommercialisation of newproducts. As a matter of fact, thesimplest way to characterise asystem (material, process) is tocompare it to the requirements ofthe standards.

Standards become valid from theday of their issuance. On the other hand, new products or processesdeveloped by contractors (or inpartnership with authorities) afterissuance of these standards may

79

The simplest way to characterise a system is to compare it to the requirements of the standards.

be of high technical interestwithout necessarily complying with the requirements of the officialspecifications or standards.

For these new products andprocesses, the contractor usuallyissues technical leaflets. Such adocument has however acommercial connotation. Jointlywith the contractors, the nationalroad authorities have developed asystem, which is an intermediatebetween a standard and atechnical leaflet. This is theTechnical Certificate “Avistechnique”. This document isissued by a committee appointedby the CFTR ( Comité Français pour les Techniques Routières), madeup of representatives of thenational road authorities andcontractors, selected for theirtechnical knowledge related to the material to be assessed. Thismeans that the composition of the committee depends on thetechnique to be assessed.

This document contains threemain chapters:

• Description of the material by the contractor;

• Main characteristics;• Technical Certificate by the

committee.

This type of document may be ofhigh support for the developmentof innovative techniques withother employers, mainly localgovernments.

To date, more than 100 technicalcertificates have been issued inthe fields of roads and bridgestechniques.

3. Procurement law needs tobe adapted

If new products are to bedeveloped to meetperformance-based specifications,road owners need to be able toexperiment with them. This is only possible if a certain degree offreedom is introduced inprocurement laws for this purpose. In this respect, recent Europeanprocurement directives haveconsiderably harmed thisdevelopment, by preventinggovernment authorities to contract with a sole contractor by mutualagreement, even on a limitedbasis, for such experimentalpurposes.

Another issue that needs to beconfronted is the adaptation of

performance bonds in thosecountries that request them as astandard practice to guarantee the performance of the work (even ifonly few European countries are in that case).

Surety companies are definitelynot used to evaluating the risksassociated with long termcontracts, where, for example,road rehabilitation work isperformed for the first years of the contract and maintenance is

80

Recent European procurement directives have considerablyharmed this development

carried out according toperformance-based specificationsfor the remaining duration of thecontract. Performance bondrequirements need to be adaptedfor this particular type of contractas to the duration of theguarantee and the amount of thisguarantee in the maintenanceperiod. Consultations with thesurety industry might help in thisregard.

Conclusion

The authors conclude thatadvances are expected all over the world, in the near future, in thefield of performance-basedcontracts as a consequence of thedevelopment of innovativetechniques, the willingness of road

authorities to adopt both aproblem-solving and a moreservice-oriented approach to theprocurement of road works.For such contracts to besuccessful, however, it will benecessary to:

• Further invest in researchand standardisation;

• Develop procurementprocedures for experimentaljobsites; and

• Adapt state of minds,procurement procedures andguarantee systems.

Exchange of information and bestpractices in all these fields willtherefore become crucial for allstakeholders.

81

This paper reports onrecent work by the SabitaInfrastructure

Development AssessmentProject (SIDAP) in prioritisinginfrastructure developmentplans in the uMkhanyakudeDistrict in north-easternKwaZulu-Natal.

The primary sources of cashincome for the majority of adultsare the state pensions provided toelderly citizens. These aresupplemented in many cases bysales of handicrafts to smallnumbers of nature tourists whotravel in the areas.

The principal source of food formost people is subsistenceagriculture, which also generatessurpluses for roadside sale.Principal infrastructure assetswithin the area include the JoziniDam and the N2 Highway a couple of fairly well maintained provincialroads, and a large number(perhaps 70,000 km) of access

roads that are often seriouslyneglected or under-maintained.

Also lying within the district arethe Greater St. Lucia WetlandsPark, Umfolozi-Hluhluwe Park, and the Tembe Elephant Park,significant attractions for tourists.At present, lack of road capacity is a principal impediment to hopes of promoting subsistence agricultural activities to larger-scalecommercial status, since thiswould require more products to be transportable cheaply andefficiently enough to becompetitively priced.

The IDP process

uMkhanyakude’s IDPs assubmitted by the national deadline in late 2002 did not prioritiseproject possibilities, or justifythem, or even estimate theircosts. The IDPs are effectively just ‘wish lists’ of possible projects,both large and ambitious.

82

Clustering infrastructuredevelopment projects foroptimal opportunity value Examples from rural KwaZulu-Natal

S Muradzikwa D Ross B Standish P CronjeUniversity of University of Consultant ConsultantCape Town Cape Town Economist

Lack of service infrastructure prevents most residents frombeing able to capitalise on the tourist flow

Extract from CAPSA‘04 paper:

It was in this context that SIDAPmet with district planning officialsin 2002 to discuss ways in whichwe could assist them in designingimproved IDPs. Priorities weredetermined during 2003, andbusiness plans for them werecompleted by February 2004. Thesummary of these is the mainpurpose of the present paper.

The uMkhanyakude IDP states that “the provision of access roads tocommunities, tourism areas,development nodes and otherareas of importance is theprecursor to any activity orprogramme planned for theseareas. Such access provides thekey to unlocking the vast potential that exists within the region.”

Clustering

The principal basis for projectprioritisation as undertaken bySIDAP is achievement of clustering for maximum investmentefficiency. SIDAP developed theproject priorities below by meansof the following reasoning.

• Firstly, they identifiedpotential assets;

• Secondly, we identifiedclusters of new infrastructurethat, if built together, couldallow full exploitation of theassets identified in step one;

• Thirdly, they estimated costs; and

• Fourthly, they estimated theexpected increases in thevalue of each asset thatwould be achieved bymultiplier effects ofinteraction with the otherassets in the cluster.

Conclusion

The authors conclude that as theirlong-term aim is the constructionof an OVA tool it must be precisely the point of the project to developthe OVA tool to decide how money might best be allocated, through a continuous process ofmodel-specification, infrastructureconstruction and recalibration, aproject prioritisation tool suitableto South Africa will be developedas the output of the project. Butfirst they need projects to test;and the ones listed might as wellbe sensible ones.

Ultimately, the OVA product indevelopment will enable thesesurveys to be complemented withrigorous and quantitativeassessment. However, it will bepart of SIDAP’s mandate topromote and seek funds for thesedevelopments now, since theirimplementation and subsequenttesting will be a crucial part of theprocess by which OVA is built tolocal conditions.

83

This paper demonstratesthat despite a small costpremium, environmentally

friendly non-tar basedprecoating materials can besuccessfully used to yield asatisfactory end result.

During the early 1980s, whenbitumen rubber was introduced,followed by increased use ofhot-applied homogenous modifiedbinders in the 1990s, roadengineers realised that theadhesion between the highlyviscous binder and the surfacingstone became a critical parameterto ensure the success of the seals. The presence of dust on the stonealso adversely affected theadhesion. A tar-based precoatingfluid showed the followingbenefits:

• Any residual dust remainingon the aggregate is bound by the precoating fluid, ensuring excellent adhesion of theaggregate to the binder,minimising the risk of looseaggregate that can damagevehicles;

• The surface will have auniform black appearance

and forms a sharp contrastwith road markings, makingnight driving considerablysafer;

• No diluted emulsion coverspray would be required.

The tar-based fluids unfortunatelyhave disadvantages associatedwith its use:

• Irritating to the skin and eyes and in some cases respiratory irritation may occur;

• When surfacing is performedin residential areas,complaints may be receivedfrom the residents due toothe pungent odour;

• Softening of rubber conveyorbelts on chip spreaders andpremature deterioration offront-end loader and rollertyres.

Studies have also shown thatprolonged contact with coal tarpitch can cause a high incidence of skin cancer (Sabita, 1995).Consequently, Colas recognisedthe need for a more user-friendlyprecoating fluid approximately sixyears ago, and after extensivetrials, a bitumen based precoatingfluid was developed. A number of

84

Bituminous based precoatingfluid for surface dressing

K Louw Colas South Africa (Pty) Ltd

The immeasurable benefits to the environment warrant the useof bituminous precoating materials

Extract from CAPSA‘04 paper:

major surfacing projects havebeen successfully completed withthis material.

The product is environmentallyfriendly, non-irritating and after ashort curing period, it iscompletely odourless. Excellentadhesion is obtained with allbituminous binders. Additivesallow the precoating material to be used with wet or damp aggregates and the chemical additives renderit suitable for coating “difficult”aggregates such as quartzites andgranites.

Typical application rates appear inTable 2.

The author concludes that with the worldwide trend afoot to moveaway from tar-based binders, ithas been shown that tar-basedprecoating fluids can besuccessfully replaced with anenvironmentally and user-friendly bituminous product. Despite amarginally higher cost premium,the immeasurable benefits to theenvironment warrant the use ofbituminous precoating materials.

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Nominal stone size (mm) 6.7 9.5 13.2 19.0

Application rate (l/m3) 14 - 18 13 - 17 12 - 16 11 - 15

Table 2: Typical application rates for various stone sizes

This bulletin paper reportson practical experience inovercoming compaction

difficulties of crushed stonebase material by the additionof a very low percentage(0.4%) of bitumen emulsion in the compaction water.

Certain G1 crushed materials aredifficult to compact to the required density, even though theirgradings are correct. In one caseit was found that the fines fraction contained a gritty particle whichprevented the proper densification of the material. This problem wasconfirmed by the compaction ofthe material on Transportek’svibratory compaction table.However, when 0.4% bitumenemulsion was added to thecompaction water, the problemwas overcome in the laboratorycompaction of the sample on the vibratory compaction table.

Armed with this information thenext step was to try the solutionin practice, with stunning results. No slushing of the base wasrequired and after drying backthe unprimed base was trafficked

in the rainy season by asubstantial amount of(emergency) traffic without anysigns of damage.

K-mould

Laboratory tests with the K-mouldon material from another showedthat the 90th percentile E-valueincreased from 435 MPa to 548MPa and the rutting resistance bya phenomenal 500& from 3.8million to 18.3 million 80 kN axleloads to cause a 10 mm rut in acrushed stone layer of 150 mm.The authors claim that the

86

Overcoming compactiondifficulties of crushed stonebase material by the addition ofa very low percentage ofbitumen emulsion

AO Bergh PB Botha CJ Semmelink H BothaCSIR CSIR CSIR CSIRTransportek Transportek Transportek Transportek

Photograph 5: Brushed area aftertrafficking and “rain damage”.

Interlocking still secure.

Extract from CAPSA‘04 paper:

dramatic improvement in thematerial performance is well worth the cost of the emulsion.

The authors conclude that the useof anionic emulsion (60%) as acompaction aid has the followingadvantages:

• The layer can be constructedin a single day;

• The layer requires lessslushing and rolling and much less water;

• Reduces damage to layer iftrafficked;

• Reduces damage to the layerdue to rain and improves thedurability of the base layer inwet conditions;

• The prime coat can bereplaced with a 1 to 6 part

anionic emulsion SS60 towater, applied with a watercart thus saving the costs ofa distributor to do thepriming;

• The emulsion prime coatdries off faster than normalprime would do in a highrainfall area with relative high humidity. This application can be repeated if required quiteeconomically;

• The higher compaction levelsthat can be obtained using acompaction aid will result inincreased densities andextended life of the basewhich is also less influencedby the penetration ofmoisture.

87

South African rural roadsgenerally carry muchmore traffic than the rural

road network in the rest ofsub-Saharan Africa with manygravel roads carrying up to1000 vpd. At the lower end,there is a vast network ofdistrict and community accessroads carrying less than 100vpd, which is largelyunimproved and maintainedonly as bladed tracks.

In addition, there are probablyhundreds of thousands ofkilometres of unimproved villageroads and streets. The potentialfor large-scale application oflabour-based road works istherefore enormous.

In the Limpopo Province it wasrealised early on that finding goodquality wearing course gravel initself constituted a major problemin many areas of the province,thus bringing the costs for a fullyrehabilitated and gravelled 5.5mwide road to about R230 000 insome instances. Aside fromdepleting an increasingly scarceresource, construction andmaintenance of conventionalgravel roads would be very costly.

An assessment of different options for the provision and maintenanceof a good gravel wearing course,in financial and economic terms as well as suitability for labour-basedoperations was carried out. Thisindicated that better use and/orimprovement of in situ material by emulsion or chemical stabilisationin combination with provision ofvarious low cost bituminous sealsresults in lower predicted life-cycle costs than the gravelling option for the roads in question.

20-year analysis period

The various options were analysed in terms of Present Worth of Costs (PWoC) and Net Present Values(NPV). The analyses are presented as both financial costs (i.e. thecost to the road authority) andeconomic costs (the cost to theroad authority and the road user)and shadow costs were used forall input costs. All analyses werecarried out over a 20-year analysis period using a discount rate of 10per cent.

Six basic alternatives wereanalysed:

• TRH 20 - Conventionalregravelling with materials

88

Labour-based bitumen roads ascost-effective alternatives toconventional gravel wearingcourses

P Paige-Green J Hongve L Sampson I CassiemCSIR-Transportek ILO Sampson Consulting CSIR-Transportek

Extract from CAPSA‘04 paper:

complying with the SouthAfrican gravel wearing course material standard;

• Non TRH 20 material withextra maintenance - Thisoption would make use of the local materials, generally with inadequate plasticity. Toavoid corrugation andravelling, additionalmaintenance would benecessary but the overallriding quality would generally be poorer than the otheroptions;

• Chemical/bitumentreatment with a seal -This option assessed thecosts of treating the in situmaterial with either bitumenemulsion or a proprietary soil chemical stabiliser. Includedin this option was that ofimporting local material fromadjacent to the road, wherethe in situ material could notbe suitably treated;

• Sand cushioning - This isan option that makes use of a thin layer of sand to protectthe gravel wearing course

from vehicle wear. It requires good conventional gravelwearing course material andregular low-cost maintenance (sand replacement anddragging), but minimises theloss of the imported gravelwearing course;

• Paved TRH 20 material -The option of paving material imported for a conventionalgravel wearing course wasassessed. This is typically a

poor alternative, as thegravel wearing coursenecessarily requires cohesion and is thus often excessivelywater sensitive to perform asa good base course under abituminous seal;

• Paved local material -Inspection of the localmaterials indicated that many of them would probablyperform successfully as abase course. The options ofsealing them directly as wellas importing local materialsfrom adjacent to the roadwere analysed.

Conclusions

It was clear from the results that:

• In financial terms, only theuse of non-TRH20 materialswith additional maintenanceand the sealing of in situ local materials have direct costadvantages.

• The economic analysesindicate that all optionsexcept the sealing of TRH20

materials and the treatmentand paving of importedmaterials are beneficial.Where the in situ materialsare not suitable for sealingdirectly, the sealing ofimported materials (2kmhaul) without treatment isthe most cost-effectivesolution in all cases;

• The total savings (economic)generally exceed thedifference between

89

The total savings (economic) generally exceed the differencebetween construction costs

construction costs on anysections of the roads: theresults thus indicate that forthe roads analysed, the TRH 20 option is mostly theleast cost-effective.

90

A design procedure wasdeveloped for theupgrading of very low

traffic volume basic accessstreets in urban environments.

Basic access streets carry very low traffic, but are forming the bulk ofthe urban street network. Theyare currently mostly gravel or dirtstreets and form the bulk of thebacklog of street upgrading andconstruction needs in the GreaterJohannesburg urban environment. The Johannesburg Roads Agency(JRA) is responsible for theupgrading of these basic accessstreets to provide access andmobility to the residents living inthese townships in themetropolitan areas of GreaterJohannesburg.

A risk managed design procedureis followed to illustrate how basicor launch risk factors need to beaddressed first before the normaldesign procedure is followed. Thelaunch risk factors are made upof:

• The geology;• The environmental factors

(including climate);• The topography;

• The community benefit andneeds.

Innovative approaches areadvocated which are linked with abetter understanding of the design domain which often are moredependant on the environmentaleffects than the traditional trafficvolume associated factors. Acatalogue of people and labourfriendly street pavement struc-tures are presented which helpgive realistic parameters to therisks involved.

Basic access streets carry lessthan 75 vehicles per day and lessthan 5 heavy vehicles per day.

Associated risks

The authors report that streetdesign process has inherentassociated risks which is notalways understood or fully takeninto account by the various parties involved in the design process.The design process has twodistinct and inherent riskassociated phases. The first phaseis to determine the launch risksassociated with the basic orfundamental aspects of the design environment (Red Book, 1998 and

91

Risk-managed design standardsfor upgrading of basic accessgravel streets

E Horak S Lacante J Hattingh S KrugerUniversity Ndodana Consulting Potgieter, Hattingh Johannesburgof Pretoria Engineers and Raspi Roads Agency

Extract from CAPSA‘04 paper:

JRA, 2003). The factors involvedin the launch risks and theirinteraction are illustrated in theconceptual diagram in Figure 1. In Figure 2 the interaction andcomponents of these launch risksare illustrated in more detail. Inorder to guide the design parties a set of questions is asked usingFigure 2 as reference and guide.

The secondary launch design riskfactors are inherently tied to these base or primary risk factors. Thesecondary launch risk factors arethe traditional design aspectsassociated with street design. Theaim is to limit or even minimisethe risks associated with the basic

risks and thereby lowering thesecondary risk factors. The questions forming the rest ofthe matrix to determine the riskprofile are:

• Is it a Greenfieldsdevelopment? (By definitionthis is a new development);

• Is it a Brownfieldsdevelopment? (By definitionthis is an establishedpreviously disadvantagedtownship with a mixedportfolio of services, levels ofservice and limitedinfrastructure);

• Is it an informal settlement/Greyfields development? (Bydefinition this is an informal

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Layout Planning

Design Domain

Traffic Services

Secondarylaunch riskfactors

Primarylaunchriskfactors

Figure 1: Launch risk factor relationships

settlement with no layoutplanning, proper services orinfrastructure, but identifiedfor upgrading).

The interaction between themechanisms of distress due totraffic volumes and theenvironment is clearly illustrated

by means of Figure 3. Normallydesigns are associated with the situation of higher traffic volumeswhere the environment is seen assecondary to it. However, for basic access streets traffic volumes arevery low and through the fore-going risk management processhave been kept deliberately low by

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DevelopmentStatus

Basic Factors

Greenfields Brownfields Greyfields

Street heirarchyestablished

Topographyreconciled withstreet layout

Services in streetreserve status

Geology detailmapped

Weak CBRstreet lengthsidentifiedMaterial sourcesidentification

Land use

Secondarydesign riskFactorsSee Fig 4

Traffic situationConstruction traffic phaseOverloading control

EnvironmentMicro-climate determinedRainfall figures

Establish design domain

Community needs and prioritiesCommunity Benefit Index (CBI)Levels of Service (LOS)Street Upgrading Priority Index (UPI)

Figure 2: Flow chart of basic access street design process

channelling traffic onto the higherhierarchy streets.

As demonstrated in Figure 3 theenvironment should be thedominant design factor in thedesign domain of basic accessstreets. For that reason theenvironment would need betterdefinition. This can be done byanswering these questions:

• Can the micro-climate bedetermined in terms ofWeinert n values?

• What are the rainfallcharacteristics?

If these questions have beenanswered it can be shown inFigure 4 that the design domainfor basic access streets can bemanaged at the lower end ofdesign standards if the basic and

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Environment

Traffic

Area ofInterest

Traffic (Million equivalent standard axles)

0 0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0

0

20

40

60

80

100

Figure 3: Traffic loading versus dominant mechanism of distress (Source: JRASynthesis document adapted from SADC, 2002)

Design domain

Guideline

Range of values

Absolute upperlimit

Absolute lowerlimit

Cost orbenefit

Zone of interestfor appropriatetechnologies

Practical upper limit

Practical lowerlimit

Figure 4. Design Domain Concept Illustration (Source: JRA Synthesis CompanionDocuments, 2003 and SADC, 2002, )

secondary launch risks wereidentified and managed.

It is suggested to use aCommunity Benefit Index (CBI) tofacilitate socio-political context inthe design decisions in astructured manner. CBI should becalibrated and based on aspectssuch as:

• Land use (residential,industrial, agricultural,educational, religious,recreation, health care, police and security);

• Functional class of streets asper the layout or communityuse;

• Community involvement inplanning structures andforums: have objectives been set and prioritised via wardcommittees? Have forumsparticipated in IntegratedDevelopment Plans (IDPs) orLocal DevelopmentObjectives (LDOs)?

• Unemployment rate andsocial indicators (Is there alabour desk or are there

community liaison persons toprovide skills profiles anddetermine unemploymentfigures?)

The authors acknowledge thatthese are not an exhaustive list offactors for consideration for thedevelopment of a CBI, but anindicator of type of factors. Theconceptual relationship betweenLOS and CBI to determine classesof Upgrading Priority Index (UPI)criteria versus each other on arelative scale are shown in Figure 5 to provide for UPI contour bands of high, medium and lowpriority.

It can be seen that it is possiblefor a street to have a mediumrating on LOS, but a low CBIrating which puts it in the low UPIcontour band. This can be used ina transparent way in determiningoverall priorities of projects.

In essence the community needscan be incorporated by answeringthese three questions:

95

High

Medium

Low

Low

Low

Level of Service (LOS)

High

High

CommunityBenefit Index

Figure 5: Street Upgrading Prioritisation Index (UPI) Chart

• What is the CommunityBenefit Index?

• What are the levels ofservice?

• What is the resultant streetupgrading priority index?

Secondary design factors

The paper presents a flow diagram which demonstrates the factorsthat need to be taken intoconsideration in the designprocess once the design domain of basic access streets have beendefined. If the primary launch riskfactors have not been addressedthey will impose themselves in the form of costly designs. Thesequestions are:

• Is the bearing capacity of the subgrade determined?

• Can the subgrade beimproved?

• Should a subbase layer beadded?

• Is any base layer necessary?

The flow diagram illustrates howthe preceding question would also determine whether not just asubbase, but also or rather only abase layer would be needed. Ifonly a base layer is needed thenext question needs to beanswered:

What would the pavementstructure look like?

This is the culmination of choicesmade to this point in the designprocess. A summary type designcatalogue of pavement structuresand appropriate materialselections is given. The followingadditional questions need to be

answered to determine choicesfrom a proposed catalogue ofdesigns for basic access streets:

• Are labour-friendly materialsand technologies availableand considered? (DoPW,1999 and JRA, 2003);

• Can phased construction beconsidered?

• Is cost lowest duringconstruction the sole factor in the final selection? (Life cycle costs, premiums on somelabour-friendly constructiontechniques and maintenanceaspects could have aninfluence in the final choice)

Further questions posed are:

• What kind of surfacing should be used?

• What storm water featuresare necessary? (JRA, 2003);

• What performance anddeterioration can beexpected?

The style of the paper is that of aprocedures document whichguides design decision makers viaseries of questions.

It was shown how aspects such as geology, the environment(climate), topography andcommunity needs coupled with the status of the layout planning canbe managed and used to lower the primary risk. It was also shownhow the design domain of suchbasic access streets is ultimatelymore strongly influenced byenvironmental factors thantraditional traffic associatedfactors.

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Once these launch risk factorshave been handled, innovativedesign concepts were illustratedfor use within such a defineddesign domain. The basis for thedesign concept rests on therealistic and risk-managedprocedure to classify thesubgrade.

Labour-friendly and innovativetechnologies are described whichwill meet the defined designdomain standards and arepresented in a user-friendlycatalogue of designs.

97

Much ad

99

101

Design of

structures

andmaterials

’

The mechanistic-empiricaldesign method widelyaccepted and implemen-

ted in South Africa for morethan two decades (hereafterreferred to as the ME designmethod) is a two-step processinvolving (i) the calculation ofexpected material responsesunder simulated loading, and(ii) estimating how many loadapplications the material canwithstand - at the calculatedresponse level - beforecracking or deforming to anunacceptable level.

Despite its many advantages, the

ME method has several problems

associated with it. Many of theserelate to the empirical element ofthe method, namely the transfer

functions that are used tointerpret the calculated responses.

This paper illustrates some of thedeficiencies of the ME designmethod. It looks at two “structural capacity” systems:

• coarse granular materials;and

• asphalt materials.

1. Granular Layer Structural Capacity Evaluation

For such materials, the structuralcapacity evaluation requires thecalculation of a Safety Factor,which was formulated by Maree(1982) in the following form:

The factor K depends on the levelof saturation. Values suggested by Maree (1982) were 0.6 for highlysaturated conditions (saturation of

103

A re-evaluation of some aspectsof the mechanistic-empiricaldesign approach

FJ Jooste Modelling and Analysis Systems

Where:N = Friction Angle ( 0), (Mohr-Coulomb Strength Parameter); C = Cohesion, in kPa, (Mohr-Coulomb Strength Parameter); F1F3 = Major and Minor principal stresses, in kPa; K = Constant relating to level of saturation.

SFK KC

=+

−

+ +

−

δφ φ

δ

32

1

452

1 2 452

tan tan

δ3 … Equation 1

Extract from CAPSA‘04 paper:

40mm Asphalt overlayE = 2500 MPa, Poisson’s Ratio = 0.40

150mm G1 overlayE = 650 MPa, Poisson’s Ratio = 0.35

250mm existing cemented layer(cracked and deteriorated to equivalentgranular)E = 450 MPa, Poisson’s Ratio = 0.35

Good quality sandy subgrade (CBR > 10%)E = 90 MPa, Poisson’s Ratio = 0.35

150mm selected materialE = 140 MPa, Poisson’s Ratio = 0.35

designer would estimate thecohesion and angle of frictionbased on published values for thetype of material in question.

To interpret the number ofrepetitions that can safely beaccommodated at a given SafetyFactor level, the author illustratesproposed limits in his Table 1.

Important finding

To illustrate the sensitivity of theME design method to materialinput parameters, a designexample (typical of manypavement rehabilitation designsituations in southern Africa) isshown in Figure 1.

The data in Figure 2 clearly showsthat small changes in pavementlayer properties can lead tosignificant variations in predictedstructural capacity. For the fourvariations considered, thepredicted structural capacityspanned over three design classes (ES8 to ES10).

Especially relevant to most designsituations is the assumed stiffnessof the subbase layer. The data inTable 2 suggest that a relativelysmall decrease in base stiffnesswould reduce the expectedstructural capacity from 10 to 4million load applications. Thisraises uncertainty about the actual structural capacity for the example

105

Variation 1

Variation 2

Variation 3

Variation 4

ES10 ES30 ES100

0 10 20 30 40 50 60

Predicted Allowable Repetitions (millions)

Base Case Pretoria Norite

Pretoria Norite, support stiffness changed from 450 to 400 MPa

Pretoria Norite, base layer Poisson’s Ratio changed from 0.35 to 0.38

Saldanha Granite

Quartzite base material

Figure 2: Influence of layer property and material type variations on granularbase layer predicted structural capacity

pavement, since the stiffness ofthe subbase will vary considerablyover a project’s length and therewould be no clear basis todetermine what the “correct”stiffness of the subbase layershould be.

2. Asphalt Layers

In the case of asphalt layers, thestructural capacity is oftenestimated using the relationshipbetween maximum horizontaltensile strain and fatigue life. Awidely used transfer function ofthis type is the Shell AsphaltFatigue Equation, which isimplemented in the following

format in the Austroads designguidelines (Austroads, 2001): As in the first example, severalvariations on the base casescenario were evaluated, and aresummarised in Table 3 and Figure4. All of the assumed variationsare deemed to be within theexpected and unavoidableuncertainties of a typical designsituation. For the base-casescenario, a binder content of 10per cent (by volume) wasassumed in Equation 3.

As in the case of the first example, the evaluation of asphalt layerstructural capacity shows extremevariations and again span overthree design classes. Again, the

106

Where:Vb = Volume of bitumen (%) Smix = Stiffness of the asphalt in Mpaε1 = Tensile strain of the asphalt in microstrain

Figure 3: Pavement situation assumed for evaluation of asphalt

40mm Asphalt overlayE = 2500 MPa, Poisson’s Ratio = 0.40

200mm Granular BaseE = 450 MPa, Poisson’s Ratio = 0.35

300mm Granular SubbaseE = 120 MPa, Poisson’s Ratio = 0.35

Subgrade (CBR > 6%)E = 60 MPa, Poisson’s Ratio = 0.35

( )

( ) ( )N

V

Sf

b

mix t

=+

56918 0856 108

0 36

5

.. .

.. ε … Equation 3

sensitivity of the predictedstructural capacity to a relatively small change in thesupport stiffness is especiallyworrying.

From the data shown in thepreceding sections, it is clear why some knowledgeable practitionersview the ME method as anencumbrance and a source ofcontention rather than a useful

107

Table3: Influence of Variations in Assumed Pavement Layer Properties andMaterial Types on Predicted Asphalt Layer Structural Capacity

Variation Situation CalculatedTensile Strain(microstrain)

StructuralCapacity(millions)

Base Case Pavement situation as shown inFigure 3, binder content 10 % byvolume

183 24.6

Variation 1 Base layer stiffness increased to500MPa

158 51.2

Variation 2 Applied contact pressure increasedto 750 kPa

223 9.2

Variation 1

Variation 2

Variation 3

ES10 ES30 ES100

0 10 20 30 40 50 60

Predicted Allowable Repetitions (millions)

Base Case Base Case as shown in Figure 3 (Vb = 10%)

Applied pressure increased from 650 tp 750 KPa

Support stiffness increased from 450 to 500 MPA

Volume of binder changed from 10% to 9% (by volume)

Figure 4: Influence of layer property and material type variations on granularbase layer predicted asphalt surfacing capacity.

design aid. It is also clear that, inthe hands of an inexperiencedpractitioner, the ME method caneasily lead to an incorrectassessment of a pavement’sstructural capacity. It seems fairto state that the ME designmethod, in its present form, isoften not a robust or consistentmethodology. This problemcentres around two principle

errors inherent in many publishedtransfer functions. These are:

(i) the implication of a predictiveability that often is not statistically sound, and

(ii) the assumption of a constantdirect or indirect relationship

between the design parameter and the repetitions to failure. A second error in principleinherent in transfer functions isthe implied constant relationshipbetween the response parameter(eg Safety Factor or TensileStrain) and the number ofrepetitions to failure or allowableload repetitions. In the case ofasphalt fatigue, this implication

would mean that the number ofrepetitions to failure wouldinfinitely increase as the tensilestrain is reduced. Similarly, in thecase of the granular materialsafety material, the use of atransfer function implies that thenumber of allowable repetitionsindefinitely increases as the Safety

108

Figure 7: Two modes of granular material behaviour (after Maree, 1982)

Example A: Safety Factor = 0.95 (less than limiting value)

Example B: Safety Factor = 1.7 (above limiting value)

Example C: Safety Factor = 1.5 (above limiting value)

High Rate ofDeformation

Low Rate ofDeformation

Threshold Value = ?

Number of Load Repetitions

ME method can easily lead to an incorrect assessment of apavement’s structural capacity

Factor increases beyond a value of 1.5.

Recommendations

The authors conclude that the twoexamples presented in this paperillustrate the sensitivity of the MEdesign method to materialproperties. It also shows how theME design method could become a source of confusion or contention,and could easily lead to anincorrect assessment of apavement’s structural capacity.

It was, however, shown that thehigh sensitivity of the predictedstructural capacity is to a largeextent related to the logarithmicform of the adopted transferfunction, which amplifies thesensitivity of the ME method, often without statistically significantempirical support. The problemperhaps does not lie in the MEmethodology, but in the mannerthat calculated working stressesand strains are interpreted.

A fundamental shift from the useof predictive transfer functions toa simplified classification system is therefore recommended, untilsuch time that conclusive andstatistically sound performancedata is available to support thedevelopment of predictive transfer function equations.

A simplified and less precise“classification approach”, asprovided, would remove many ofthe contradictions from themethod. The author also believesthat a classification approachwould offer significant advantagesover the quantified transferfunction approach. Mostimportant, perhaps: such aclassification system would notimply an inappropriate level ofprecision. Practitioners andresearchers would thus beexplicitly aware of the limitationsof the design method, and couldtake this into account duringdesign and development activities.

For researchers and developers,the use of a classification systemwith coarse precision is perhapseven more important. This isbecause the explicit lack ofprecision and predictive ability ofsuch a system will ensure that theME method is implemented in anappropriate manner, and thatfuture research activities takecognisance of the limitations of the state-of-the-art. It will also ensure that complex extensions of themechanistic empirical method areonly considered once thevariability in long termperformance has been adequatelyexplained and addressed.

109

Under the Chair inPavement Engineering,University of

Stellenbosch, in 1998performance testing of roadsurfacing seals was initiated.

The Model Mobile Load Simulator(MMLS) was identified as asuitable instrument, and a testmethod developed. From 1998 to2002 a test regime using fivedifferent seal binders, and threetemperature regimes, was

implemented. A method wasdeveloped to enable evaluation ofthe seals’ behaviour. The sealswere evaluated in terms of theperformance criteria determinedthrough assessment of literatureand the research process (Milne,2004). The interaction betweenthe influencing factors, andperformance criteria are providedin Figure 1.

MMLS testing enabled the sealperformance evaluation in Talbe 1

110

Performance based roadsurfacing seal evaluation:empirical testing

TI Milne MFC van de Ven M HuurmanAfricon Delft University Delft University

KJ Jenkins A Scarpas C KasbergenUniversity of Stellenbosch Delft University Delft Un iversity

Summary: Seal Performance Scale100 maximum: worst0 minimum: best

Binder Overall performance

Test regime

100C(cold)

Ambient 500C(Elevated)

Binder modified 80/100 pen grade with:

3% SBR 0-22 19 17-22 0-6

3% SBS 0-28 28 0-16 6-15

3% EVA 11-28 17 11-28 11

20% bitumen rubberBR

- Tosas- Colas

14-3911-56 17

14-3511-33

25-3917-56

80/100 Penetrationgrade

22-56 22 31 56

Table 4: Summary of Seal Performance

Extract from CAPSA‘04 paper:

to be established. Each bindertype has a specific regime where,for the tested base type,performance is enhanced. This issummarised in Table 5.

Milne et al’s work continues in asecond paper that investigatesSouth African seal design areaswhere review or updating issuggested. Seal performance

111

Performance criteria for Performance evaluation

DeformationCrackingAdhesion

Aggregate crushing/polishing

Performance Testing(APT)

• Binder

• Aggregate

• Seal (design)

Seal

Influencing Factors

Non-ControllableControllable

• Environment (temperatures and moisture)

• Traffic

Figure 1: Interaction of Influencing Factors and Identification of PerformanceCriteria

Binder Ranking*

Ranking (1 best, 5 worst), (BR Consolidated)

Regime 1 2 3 4 5

ColdAmbientElevated

20% BR3% SBS3% SBR

3% EVA3% SBR3% EVA

3% SBR3% EVA3% SBS

80/10020%BR20%BR

3% SBS80/10080/100

Overall 3% SBR 3% SBS 3% EVA 20% BR 80/100

Table 5: Binder Performance Ranking

Performance Criteria

* 80/100 pen grade bitumen modified as shown

criteria are examined, and theneed for a seal design methodbased on mechanistic principles isproposed. A prototype sealbehavioural model initiating thedevelopment of a mechanisticdesign tool for seals and thinsurfacing layers was developedusing Finite Element Methods(FEM).

Benefits

The potential benefits to practiceof the mechanistic design tool willbe enhanced as the design modelis developed, and initial contribu-tions to practice, such asenhancing the understanding ofthe behaviour of seal components, are discussed, with thedemonstration of the first multipleelement seal FEM model. Theoriginal initiation of a three-dimensional seal model wasundertaken in 2002 at TechnicalUniversity Delft, using the CAPAresearch programme, and the TUDelft computer resources ofrequired computational ability.

Work continued on thedevelopment of the seal model in2003, resulting in the prototypeseal model, of binder and sealstone. This is the subject of thispaper. Subsequently a base meshhas been developed which isavailable for further development.For the development of amulti-element (stone, bitumen,base and wheel-load) prototypenumerical model, thedetermination of applied loadsrepresenting as real a reflection as possible of actual traffic loading on seals was required. A detailedassessment and interpretation of

current available data, focused onthe geometry of the textured FEMmodel, was undertaken with theobjective of defining a prototypemodel traffic load.

Two imposed load types wereconsidered for an “average” twoaxle heavy vehicle:

• Driven rear wheel;• Rolling front wheel.

Of importance to a seal model was the load on:

• A textured surface, asrepresented by the sealaggregate;

• Contact stresses, tangentialand vertical, imposed by thevehicle tyre.

The determination of load applica-tion type, and implementation, for FEM modelling, allows inclusion ofthe above load types, e.g.:

• Dynamic “single wave” loadapplication or modelled staticload imposed a number oftimes to simulate dynamiceffects;

• Loading applied to a texturedsurface, with texture ofdifferent depths;

• Focus on the seal model wasthus on the affect of textureon the transfer of bulkstresses from the tyre tomicro-level stresses in theseal stones.

Some results

The ability of the prototype modelto differentiate between bindertypes was assessed by comparing

112

two binders: “straight” penetration grade and a modified binder.

A temperature of 250C wasdecided upon for materialparameter determination, as thisis in the accepted zone ofviscoelastic behaviour. 70/100 pen

grade binder, and SBS modified (3%) binder. Figures 8(a) and8(b) demonstrate the behaviour of the different binder types, interms of cumulative displacements under four truck passes. Thedisplacements of the top, central

113

Run 1: Pen bitumen; round stone, interface bitumen;Displacements top of centre stone

Time step of Front and Back Axle

Run 3: SBS; round stone, Bitumen InterfaceDisplacement Top of Centre Stone

Time step of Front and Back Axle-2.00

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

-2.00

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

-3.00

Displacement Lateral Displacement Longitudinal Displacement Ver tical

Displacement Lateral Displacement Longitudinal Displacement Vertical

Figure 8 (a): Pen grade bitumen: Displacement under sequential loading: 250C

Figure 8 (b): SBS modified bitumen: Displacement under sequentialloading: 25 0C

node of the central stone isprovided for the comparison.

Conclusion

It is evident that there exists aneed for the development of afundamental model for sealperformance prediction tocomplement current South Africanseal design codes and experience.The prototype model is amicro-mechanical model forsurfacing seal performanceprediction. Of course, the modelmay be loaded by various loads(also temperature loading), and itmay be used in combination withmore realistic material models.

On the basis of the linearcalculations discussed, it isconcluded the model will prove togive insight into seal behaviourand with development should offer the following:

• Distinction betweenphysical/chemical adhesion(IF-behaviour) and

mechanical adhesion (stoneshape);

• Enable better understandingof loss of adhesion and thusloss of stone, which is aprime cause of seal damage;

• To provide insight into stressand strain development in the binder;

• To explain various types ofcohesive seal cracking; and

• Prediction of deformation inthe binder resulting in stonerotation.

As a result of the above, insightinto stresses in the stone/binderinterface is obtained.

Within the philosophy for themodel discussed, future work intothe prototype will include theaddition of a base layer, to enableinteraction between base and sealto accommodate punching ofstones into the base. In addition,realistic material models will haveto be developed to further refinecomputational output the modelprovides.

114

The bitumen foamingtechnique by addingwater to hot penetration

grade bitumen, and therebycausing a temporary expansion to enable coating of coldaggregate, was used in a pilotproject on a large scale on theSame-Himo road in NorthernTanzania, reconstructed in theperiod 1990 to 1992. Partlynatural, screened gravel andpartly milled old cementstabilised pavement materials,were stabilised using abitumen content of 4.4%applied without any addition of cement filler.

A comprehensive pavementmonitoring programme has been

on-going since construction of theSame-Himo road, and the lastrecordings were carried out late in 2003. The following areconclusions of the findings afterthe pavement monitoring:

• The pavement utilisingnatural gravel base coursestabilised with foamed

bitumen has performed verywell on a heavily loaded trunk road in Tanzania. Thepavement is currently in anexcellent condition;

• The pavement on theSame-Himo road is currentlynear the end of its 15 yearsdesign period and has almost received the 5 million E80s itwas designed to withstand;

• The pavement has receivedno resealing or other periodic maintenance sinceconstruction;

• There has been no potholedevelopment on the road;

• There is no excessivedevelopment of rutting orsurface roughness on theroad;

• Sealing of individual crackshas been undertaken onindividual sections;

• The pavement utilisingnatural gravel stabilised withfoamed bitumen hasperformed very wellthroughout most of its design period on a heavily loadedtrunk road in Tanzania.

115

Bitumen foaming - an innovative technique used on a large scalefor pavement rehabilitation inAfrica

C Overby R Johansen M MatakaPublic Roads Administration ViaNova Consulting Ministry of WorksNorway Engineers, Norway Tanzania

Extract from CAPSA‘04 paper:

The findings suggest that the TG2 design manual could produceconservative designs

Placed material

Following the Same-Himo pilotproject the bitumen foamingtechnique has had considerableuse in large scale pavementrehabilitation and new

construction in Tanzania andZambia during the 1990s,amounting to well over one million tonnes of placed material.

The method was subsequentlyadopted in the Tanzania Pavement

116

Design traffic(million E80s)

Asphalt Academy, RSA, base courselayer thickness(mm)

Design traffic(million E80s)

Tanzaniastandard basecourse layerthickness (mm)

0.001 - 0.0030.003 - 0.0100.01 - 0.0300.03 - 0.1000.1 - 0.3

75100100 - 125100 - 125100 - 150 < 0.2 60

0.3 - 1.0 100 - 175 0.2 - 0.50.5 - 1.0

80100

1.0 - 3.0 125 - 175 1.0 - 3.03.0 - 10

125150

Table 1: Layer thickness, bituminous base course (foamed bitumen)

Assessment, Same-Himomonitoring sections 2003/04

*) Criteria for roads intraffic load class with >3 million E80s

Deflection (90percentile, lightlycem)

WARNING (Measured only once,after 10 years in service. Criteria for ‘lightly cemented’ basecourse is used)

Sound: <0.35mmWarning: 0.35 - 0.85mmSevere: >0.85mm

Roughness SOUND (One section barelyapproaching WARNING, however this case is related to subsoilconditions rather than pavementdistress.)

Sound: IRI < 3m/kmWarning: IRI 3 - 6mSevere: IRI > 6m/km

Rutting (90percentile)

SOUND/WARNING (ApproachedWARNING after 7 years sinceconstruction, but rutdevelopment has levelled outand there has been no increasesince that time.)

Sound: < 5mmWarning: 5 - 15mmSevere: > 15mm

Cracking SOUND (On individual sectionsWARNING to SEVERE, howeverthis is related to subsoilconditions

Sound: < 10% (all cracks)Warning: 10 - 30% (allcracks)Severe: > 30% (all cracks)

Table 2: Condition rating of the Same-Himo monitoring sections

* According to Tanzania Pavement and Materials Design Manual - 1999.

and Materials DesignManual-1999, to which acomparison with the AsphaltAcademy manual of South Africahas been made (see Table 2).

Discussion:

The findings of the Same-Himoinvestigation suggest that the TG2 design manual could produceconservative designs. Long TermPavement Performance (LTPP)results have shown this section offoamed bitumen stabilisedpavement to out-perform TG2predictions.

117

The stress-dependent andnonlinear behaviour ofgranular pavement

materials is well known. It ishowever expensive and timeconsuming to determine theproperties of such materials ina laboratory — i.e. usingtriaxial testing.

As part of pavement investigation, the drop sequence of the FallingWeight Deflectometer (FWD)measurements can be successfully adjusted and used in thedetermination of materialcharacteristics. Experience froman investigation of pavements onhighly trafficked roads is used to

demonstrate the role of a FWD inthe determination of materialproperties to describe thenonlinear and stress-dependentmaterial behaviour of in situpavement materials.

Two different approaches are

compared for determining thestress-dependent materialparameters of a pavement,namely a linear-elastic and astress-dependent method. Tofacilitate the analysis, FWDdeflections were measured at fourdifferent load levels, with fivedrops at each load level.

In the first method,back-calculations of the layermoduli were made using alinear-elastic finite elementmethod. By repeating thisprocedure for each of the loadlevels, an indication of thestress-dependent behaviour couldbe obtained.

The benefits of using a finiteelement model as opposed to aconventional mechanistic analysismethod, are shown in Table 5. The finite element method providesmore realistic stiffness for thedeeper layers in the structure, and to some degree addresses the

118

Determination of stress-dependent material propertieswith the FWD for use in thestructural analysis of pavements

SJ Bredenhann KJ JenkinsEntech Consultants (Pty) Ltd University of Stellenbosch

The finite element method provides more realistic stiffness forthe deeper layers in the structure

Extract from CAPSA‘04 paper:

119

overestimated subgrade modulicommonly expressed inback-calculations of FWD insouthern Africa.

The second method of back-calculation required the develop-ment of specialist software, i.e.PaveFEL, by SJ Bredenhann, forthe analysis. Stress-dependentbackcalculation is anunconventional approach and thefollowing features should be noted:

• With this method the materialparameters, eg. K1, K 2 of aspecific model, are back-calculated rather than theE-moduli, as in the linear-elastic case. It is only reallypossible to calculate onematerial parameter at a time,so one parameter is selectedand the second parameter isback-calculated;

• A number of different material models can be used (andwere) with this approach,namely the Bulk-Stress (K-u)model, the Huurman-vanNiekerk model, the Uzanmodel and the Thomson andElliot bi-linear model. A model such as the Huurman-vanNiekerk model is complicatedand has many parameters.

Prior knowledge of some ofthe material parameters, orthose of similar materials, ishelpful in estimating otherparameters. Even with theK-u model, it is recommen-ded that the K2 value isbased on material testingand only K1 is determined.The procedure followedincluded the initialback-calculation of thematerial parameters for the40 kN drop weights, followed by the testing of theseparameters for the 30kN,50kN and 60kN levels. If the fit is not satisfactory for theother load levels,adjustments can be made tothe parameters. Theseadjustments are not maderandomly, and should takecognisance of the relevanceof the parameter, eg. in theK-u model, K1 indicatesmaterial quality and density,while K2 is the measure ofstress dependency. Thematerial parameters are notmutually exclusive, andparameter sets are therefore not necessarily unique.Adjustment of oneparameter can require arepeat of the whole fittingprocess.

Layer Elastic Modulus (MPa)

Finite Element Linear-Elastic

200 mm Base Course 490 509

150 mm Subbase 100 91

250 mm Selected Subgrade 70 91

400 mm Subgrade 1 280 123

400 mm Subgrade 2 370 486

Table 5: Comparison of Back-calculation with Linear-elastic Multilayer and FiniteElement Methods for Normalised 40 kN Load Level

Application

This paper provides an example of a pavement rehabilitation designusing the material parametersobtained from FWD back-analysis.For advanced pavement designusing stress ratios in granular andfoamed bitumen treated materials, it is essential to use the materialparameters for the finite elementanalysis.

Conclusion

It has been shown that the FWDcan be used to extract more

information out of an existingpavement than is evident incurrent practice. Parametersdescribing the characteristicmaterial behaviour of in situpavement material can besuccessfully determined byadjusting the FWD drop sequence. Material parameters for the foamtreated material were determinedthrough triaxial tests in thelaboratory. The combination ofFWD measurements andlaboratory testing proved to be aneconomical way to develop moresophisticated pavement designmodels.

120

There is some incentive forpractice to come to termswith the reality of tyre

pressure distrib- utions, whichare signifi- cantly differentfrom those of 1995, as a basisfor transfer functions used inanalytical-empirical designmethods.

Changes in the stress patternsunder heavy loads and high tyreinflation pressures are notcurrently compensated for in

design methods, while largequantities of available traffic dataare underutilised in design. Theaim of this paper is to presentrecently measured tyre inflationpressure and axle loading dataand to utilise this information inthe structural investigation ofthree different pavementsstructures on the N3 Toll Road byemploying a sensitivity analysisapproach to mechanistic design. The measurements are employedin

a statistical approach to currentmechanistic design principles todevelop conclusions as to the most appropriate choice and applicationof stress and load parameters.

No attempt is made to re-evaluate the current design methods, butmerely to provide an additionalfunction to assess the risk ofaccelerated pavementdeterioration, within the acceptednorms and proven practice ofpavement design.

Freight transport in South Africawas fully deregulated in the early1990’s, in close conjunction withthe increase in Gross CombinationMass (GCM) to 56 tonnes and theincrease in axle load to 9 tonnes in 1996. The South African GCM iscurrently far in excess of thecorresponding limits set in manyother countries. Freighttechnology advancements in fuelefficiency and improvements intyre technology have resulted innot only excessively high loads,but also tyre inflation pressures

121

The effect of axle load spectraand tyre inflation pressures onstandard pavement designmethods

BS Morton E Luttig E Horak AT VisserNinham Shand Ninham Shand University Unive rsity (Pty) Ltd (Pty) Ltd of Pretoria of Pretoria

The South African Gross Combination Mass (GCM) is currently far in excess of the corresponding limits in many other countries

Extract from CAPSA‘04 paper:

reaching the 1000 kPa level onstandard haulier vehicles; a rangethat was, until recently, reservedfor the use of super-single tyresonly.

The combined effect of all thesefactors is unprecedented loadingand applied stresses on majorroads throughout the country.Toll road concessions are beinginstituted on a national scalethroughout South Africa, withmany additional toll concessionsplanned within the southernAfrican region over the next 5years. Control of loading is acrucial aspect of toll operationsand thus sophisticated equipmenthas been introduced.

Weigh-in-motion equipmentcurrently provides large databases of pavement loading and truckconfiguration information.The authors claim that theadvances of the freight industry

and ever increasing riskassessment required by tolloperators have outstrippedimprovements in design practicesutilised internationally and insouthern Africa.

Axle loading The load of a given set of tyres isexpressed in terms of the weighteach tyre supports, the contactpressure exerted at thetyre/pavement interface and thenumber of tyres. Comparison ofSouth African and internationalaxle load limits illustrate that thevariation in maximum axle load iscontained between the 8 to 9tonne limit. The GCM in SouthAfrica is currently set at 56 tonnes with the maximum standard axleload of 9 tonnes.

Tyre inflation pressure

Tyre pressures have a significanteffect on the stress in the pavement. This isparticularly relevant onthe upper layers (i.e.surfacing and base). Tyre pressures on truck tyreshave increased fromaround 555 kPa in 1960’s to approximately 750 kPa in 1995 (De Beer, 1998).

Three pavement sectionsof the N3 Toll Roadconsisting of two generalpavement structures,were identified. Thepavement structures(designated Pavement A,B and C) are shown inFigure 2.

122

Tyre Inflation Pressure (kPa)

1974 1995

0

5

10

15

20

25

100 200 300 400 500 600 700 800 900 1000 1100 1200 130014001500

Figure 1: Historical measured tyre inflationpressure distributions (De Beer et al, 1999)

Equivalent Damage Factors

The philosophy of EquivalentDamage Factors (EDF) wasselected for the expression of theeffect of increased tyre inflationpressure and axle load onpavement life in the statisticalformulation of the “weightedeffect” of these two parameters on the analysed pavements.

Figure 5 illustrates the cumulativedistribution of the random axleload sample captured. From thecurve it is evident that overloading amounts for approximately 10% of all axles measured. Note thatoverloading in this case is definedas axle overloading and not grosscombination mass.

Conclusions

The authors conclude that trucktyre inflation pressures haveincreased significantly over the

123

Thick asphalt wearing courseThickness = 150mm

Crushed stone base (G2)Thickness = 200mm

Cement stabilised subbase (C3)Thickness = 150mm

Natural gravel selected layer (G7)Thickness = 250mm

In-situ subgrade

Thin asphalt wearing courseThickness = 40mm

Crushed stone base (G1)Thickness = 150mm

Cement stabilised subbase (C4)Thickness = 300mm

Natural gravel selected layer (G7)Thickness = 150mm

In-situ subgrade

Thin asphalt wearing courseThickness = 40mm

Crushed stone base (G2)Thickness = 150mm

Cement stabilised subbase (C3)Thickness = 250mm

Natural gravel selected layer (G7)Thickness = 150mm

In-situ subgrade

Pavement A Pavement B Pavement C

Figure 4: Pavement structure evaluated in investigation

0

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 2 3 4 5 6 7 8 9 10 11 12

Load (Tonnes)

Figure 5: Cumulative distribution of axle loads

last decade, with over 84% of allmeasured truck tyre inflationpressures exceeding the generallyaccepted design norm of 700 kPa.

The effect of truck tyre inflationpressure plays an important rolein combination with axle load inthe deterioration of flexible asphalt pavements.

The trucking industry hasoptimised axle loading,successfully making use of the 5% grace on axle load prosecution.Over 35% of all axle loads fallwithin the previous axle load limitof 8 tonnes and the currentmaximum prosecution load of 9.45 tonnes.

E80/HV ratios as specified in thedesign method are outdated, and

need to be re-evaluated,particularly when applied to highprofile roads carrying major trucktraffic levels. By incorporating theactual truck and tyre inflationpressure distributions in analysis,the sensitivity of designs tooverloading and overstressing canbe quantified.

The results of the analysiscontained in this report clearlyillustrates that truck tyre inflationpressure needs to be re-evaluated in currently utilised mechanisticdesign methods, both with regards to applicability of the designmethod and the recommendationincluded in the design methodregarding standard norms of truck tyre inflation pressure.

124

Image analysis techniqueshave been used to providequantitative information on

the orientation anddistribution of aggregates inasphalt after gyratory,vibratory and slab compaction.

Consistency in compaction in thelaboratory and on site is necessary if accurate correlation is to occurbetween laboratory performanceand the observed site behaviour.Since the method of compactionhas a direct impact on theaggregate orientation and internalstructure of an asphalt mixture,

this paper discusses the observeddifferences in the asphalt matrixas a function of compaction andthe resulting differences inmechanical performance.

Gyratory Compaction

The SHRP recommendedcompaction parameters were used

in the gyratory compaction study.

Vibratory Compaction

The vibratory compaction wasachieved by a vibrating Kangohammer, applied to both faces ofthe specimen (prEN 12697-32,2000). Slab Compaction

The slab compactor produces slabs 300 mm X 300 mm X 100 mm inheight. This method is the mostmechanically similar to site ‘roller’compaction.

Mechanical performance andthe asphalt matrix

Mechanical performance testingwas undertaken on the specimensto investigate the effect of themode of compaction. Two types of testing have been reported in thispaper, Repeated Load Axial Test

125

Effect of asphalt mixturecompaction on aggregateorientation, segregation andmechanical performance

AE Hunter GD Airey AC Collop Nottingham Centre for Pavement Engineering, UK

Extract from CAPSA‘04 paper:

This paper highlights the effect of aggregate structure onpermanent deformation

(RLAT) and the Indirect TensileStiffness Modulus (ITSM).

Repeated Load Axial Test

In the RLAT a number of loadpulses are applied to thespecimen, on the flat (cut)surface, with the resultingdeformation recorded. The axialstrain obtained at the end of thetest is a valuable measure of thespecimen’s resistance topermanent deformation. This testis destructive and was carried out

using the following test parame-ters:

• Test Temperature — 300C; • Test Duration — 7200 secs

(3600 cycles), with a cycleconsisting of 1 second ofapplied load followed by a

one second recovery period;• Axial Stress — 100 kPa;• Conditioning Stress 10 kPa

for 120 seconds.

In this study 10 specimens weretested for each mode ofcompaction, the results aresummarised in Table 3.

The results indicate the mouldbased compaction methodsproduce specimens which areapproximately twice as resistant to permanent deformation as theslab compacted specimens.

Indirect Tensile StiffnessModulus

The stiffness moduli of the asphalt specimens were measured usingthe ITSM test, which wasundertaken using the followingtest parameters:

• Test temperature — 200C;Loading rise-time — 124milliseconds;

126

Mode ofCompaction

Mean Air Voids (%) Mean Permanent Axial Strain (%)

Gyratory 6.1 0.55

Vibratory 6.3 0.65Slab 6.4 1.21

Table 3: RLAT results for gyratory, vibratory and slab compaction

Mode of Compaction Mean Air Voids (%) Mean Stiffness (MPa)

Gyratory 3.05 7906

Vibratory 6.03 6762

Slab-roller 2.99 7321

Table 4: ITSM results for gyratory, vibratory and slab compaction

• Peak transient horizontaldeformation — 5mm on a 150 mm diameter specimen.

Thirty specimens were manufac-tured and tested for eachcompaction method with theresults presented in Table 4. The air voids content of thevibratory specimens wasapproximately twice that of thegyratory and slab compactedspecimens making comparisonsdifficult. However the meanstiffness of the gyratoryspecimens is 8% greater than that of the slab compacted specimens.This result is commented on in the

context of the aggregate structure in the discussion.

Summary

This demonstrates that mechanical performance testing highlights the effect aggregate structure has onpermanent deformation resistance and stiffness modulus. Mouldbased compaction methods appear to create specimens which areapproximately twice as resistant to permanent deformation (RLAT) asslab compacted specimens. A lessdistinct difference between theperformance of the specimens has been observed in the stiffnessmodulus (ITSM) tests.

127

Situated halfway betweenthe cities ofPietermaritzburg and

Durban, Provincial Main Road(MR) 504 provides primaryaccess to a large asphalt plant, a commercial quarry and apre-cast concrete productsfactory.

A 700m section of this road,located on a steep gradient(+10%), was upgraded toblacktop standards during 1995 by constructing a single layer offoamed bitumen treated material

on top of a prepared subbaselayer. The single slurry seal thatwas applied soon afterconstruction proved adequate forthree years before requiring acompetent surfacing.

In 1995, this steep section wasidentified as a candidate projectfor upgrading using a technologythat was then in its infancy inSouth Africa - foamed bitumenstabilisation. Accordingly, afoamed bitumen treated base wasconstructed as an experiment

using two different types ofmaterial.

The road has performed beyondoriginal expectations and thispaper investigates the reasonswhy. Initial construction recordswere reviewed to obtain thedetails of what was actually built.Two years after construction, theCSIR evaluated the pavement andcompiled a report with predictionsfor life expectancy.

Seven years later, the road is stillperforming well in spite of the

large number of heavy loadsemanating from the crusher,asphalt plant and pre-cast yard.It has exceeded the life spanoriginally predicted and is showing few signs of distress.

Construction

During March 1995, material forthe new base of MR504 was mixed using the Soter plant and placed in stockpile. Two different types ofmaterial were used. The foamedbitumen application rate for the

128

A LTPP exercise on a foamedbitumen treated base on R504in KwaZulu-Natal

D Collings R Lindsay R ShunmugamLoudon International KZN Department KZN Department of Transport of Transport

High deflections are not synonymous with early failure

Extract from CAPSA‘04 paper:

reclaimed asphalt pavementRAP/crusher dust blend was 1.7%and 3.5% for the weatheredgranite material/1% hydratedlime.

Both material stockpiles weretested two weeks after mixing and again two months later. The testresults are shown in Table 2.These results showed that, unlikethe weathered granite mix, theRAP blend experienced nosignificant degradation as a resultof standing in stockpile for anextended period. Both materialsremained in stockpile for a furthermonth before being transported to the road and used in theconstruction of a new base layer.

Section A was constructed with175mm of foam-treated RAP,Section B with 175mm of foam-treated granite and Section C with150mm of foam-treated granite.

Construction

The work was carried out by oneof KZN DoT’s construction units,commencing with the new subbase layer. Foamed bitumen treatedbase construction started on 23rd

June 1995 with the second RAPsection (A2). Material was hauledto site from stockpile (approx-imately 10km), tipped, placed bygrader and compacted whilsttraffic was accommodated inhalf-widths. Thereafter, some100m was constructed each daywith the last section (C) beingcompleted on 12th July 1995.Densities achieved for the foamedbitumen treated material(measured as a percentage ofModified AASHTO dry density)were as follows: Section A:100.9%; Section B1: 95.6%;Section B2: 102.6%; Section C101.4%.

Benkelman Beam

Surface deflection measurementswere made across the trialsections using a Benkelman Beamin July 1995 and February 1996.Some sections of the trials withfoamed bitumen showed areduction deflection after sevenmonths of trafficking (on steepuphill grades with heavily ladentrucks) compared with sections ofincreased deflection with downhillgrades and unladen trucks. At best

129

Material RAP/crusher dust blend Weathered graniteParameter/property Mix

designDelay after mixing Mix

designDelay after mixing

2 weeks 2 months 2 weeks 2 months

Dry stability kN 28 23.7 23.7 23 13.7 12.5

Soaked stability kN 19 17.4 19.1 16 11.5 7.3Retained stability % 67.9 73.4 80.6 69.6 83.9 58.4

Resilient modulusMPa

1950 1503 1453 2350 No test No test

Dynamic creep MPa 22 No test 14.5 94 No test 83.3

Table 2: Results of tests on stockpiled material

the deflection measurements were highly variable.In 1997 KZN-DoT employed CSIRTransportek to assess threeseparate pavements that wereconstructed with foamed bitumen- treated bases during 1994 and1995, including MR 504. Rut depth measurements thatwere made in the left-hand(downhill) lane showed thefoamed RAP to have an average of 3 -7mm of permanentdeformation, and the foamedgranite to have 4-15mm ofrutting.

Three separate exercises werecarried out to derive the resilientmoduli values, namely: empirically using the penetration rate of aDCP cone, back-calculated usingthe results of the FWD survey, and repeated- load indirect tensiletests on core specimens.

The results are shown below:

Traffic

The loading that this pavementhas carried since 1995 isestimated as being annualproduction figures for the crusher,asphalt plant and block production industries that use R504:

RHS (uphill) lane + 2 x 106 E80s;LHS (downhill) lane + 3 x 105

E80s.

The deflections on the right hand(uphill) lane indicate that, ingeneral, little has changed overthe eight-year interval between1996 and 2004 in terms ofpavement response to load.Deflections on the last 60m haveactually reduced. The pattern forthe left hand lane is lessconsistent, with both increasesand decreases in deflections.

In 2004, a subsequentinvestigation was undertaken incorporating DCPs, Benkelmanbeam and cores with appropriatetesting

Discussion

The two different materials treated with foamed bitumen in thepavements on MR 504 appear tobe performing beyond theirexpectation.

Predictions for structural capacityproposed by the CSIR in their1997 report (FWD and DCP tests)as well as those derived using thetransfer functions in the recentlypublished TG2 guideline document and the AA Loudon investigation

130

Section Section Resilient Modulus values (MPa) derivations

DCP analysis FWD back-calculated Repeated load test

A 1326 1771 1355

B1 471 360 1261

B2 587 1230 1295

C 964 1715 No cores

Table 7. Stiffness moduli derived from different sources

(cores, DCP and BenkelmanBeam) appear to be veryconservative.

The traffic loading pattern carriedby this pavement presented anideal opportunity to check one ofthe theories postulated by HVStest results: the resilient modulusof a foamed bitumen treatedmaterial reduces when subjectedto repeated loads. The heavytraffic carried by the right hand(uphill) lane on MR 504 is farhigher than that carried by the left hand (downhill) lane. However,after nine years of service, there is little evidence that there is anyappreciable difference between the

behaviour of the two lanes. Tothe contrary, judging by deflection measurements, the heavily loaded lane on the foamed bitumentreated RAP section appears to bein a superior condition.

Foamed bitumen treatment isclearly different from other typesof stabilisation. The investigations reported in this paper have shownthat high deflections are notsynonymous with early failure, aswould be the case with asemi-rigid pavement. The modelsthat have been postulated forperformance predictions areclearly imperfect and need to berevised.

131

Having studied thespectrum of trucks onthe N3-TCC (Traffic

Control Centre) system nearHeidelberg, and applyingfour-pad Stress-In-Motion(SIM) technology, the authorspropose improved loadingmodels for thinly surfacedflexible pavement designs.

From Figures 14 and 15 in thepaper (reproduced here) it is clear

that especially for pavements with thin asphaltic surfaces, includingsurfacing seals, the verticalcontact stress footprints obtainedfrom real world trucks arenon-circular and non-uniform. Itis the opinion of the authors that“shape and profile” of the contactstresses (3D) should therefore beintroduced during the design stage of pavements and pavementsurfacings.

132

Tyre-pavement interface contact stresses on flexible pavements— quo vadis?

M De Beer C Fisher L KannemeyerCSIR Transportek CSIR Transportek SANRAL

Extract from CAPSA‘04 paper:

Figure 14: SIM test 297: Vertical contact stress contour footprint of a normal“n”-shape - axle 1 - steering tyre - right side

133

The way forward

Evidence from the measured SIMdata and limited analysis so far,points to the fact that non-uniform tyre-pavement contact stressesshould be used for pavementdesign, instead of the usualuniform and circular shapes, and:

• Improved tyre loadingmodels are crucial forimproved optimisation of thepavement design efforts forflexible pavements with thin(50 mm) surfacings, including textured seals.;

• For overloaded/underinflatedtyres the fatigue “life” of

thinly surfaced flexiblepavements will besignificantly reduced as adirect result of increasedhorizontal tensile strainsunder the edges of the tyre.

Finally, the authors recommendthat an improved load equivalency concept for damage of thesurfacing of flexible pavements be investigated. The rathersimplistic power law for relativedamage based on load level onlyappears not to be the best optionfor the design of thin surfacings of flexible pavements.

Figure 15: SIM Test 306: Vertical contact stress contour footprint of abnormal“m”-shape - axle 5 right outer tyre

The evolution of bitumenspecifications has beendramatic in the last 15

years. Simple empirical testsbased on mechanicalproperties formed the firsttypes of binder tests. Morerecently however, fundamen-tal, visco-elastic and damagecharacterisation methods have been adopted.

Changes in specifications havebeen motivated by various factorsand have had various conse-quences in different parts of theworld. In this paper, the authorsbring together their experience ofworking in three differentcontinents, to evaluate variousbitumen specifications and discuss merits of different concepts usedfrom as early as 1950 to 2003.

In the early 1990’s, the StrategicHighway Research Program(SHRP) project in the USA resulted

in the introduction of SuperPavebinder specifications afterdecades. As a result, the bitumenspecification world was changed

dramatically by twodevelopments:

• The introduction of “new” rheological testing methods;

• The concept of PerformanceGrading (PG) to relatepavement , temperature andtraffic conditions tofundamental properties. This resulted in the developmentof binder-blind specifications(regardless of whethermodified or not).

The authors claim that bothdevelopments were successfullyimplemented in the USA but arelagging in other parts of the world. One of the logical reasons is thecost and complexity of the newrheological test equipment.Although the concept is bestimplemented using rheologicalproperties, it can be applied usingvarious types of test results, eg.those derived from Penetrationand Softening Point.

Europe

Penetration grade bitumenspecifications in Europe have

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Concepts used for developmentof bitumen specifications

MFC van de Ven KJ Jenkins HU BahiaDelft University University of University of Stellenbosch Wisconsin

It is possible to establish an indirect PG system without costlybinder testing equipment

Extract from CAPSA‘04 paper:

always been seen by the industryas indirectly related toperformance. The Bitumen Test Data Chart(BTDC) as developed by Heukelom and van der Poel nomograph areexamples of tools for use in thisperformance link.

Since 1990, the Europeanspecifications for paving gradebitumens have been developed intwo stages:

• First generation: Productionof harmonised specificationsand test methods for pavingbitumen. For use in Europe,based on national standards;

• Second generation: Producespecifications that are moredirectly Performance-Related, with existing or newproperties and test methodswhere appropriate.

United States

The first bitumen specificationimplemented by the AmericanAssociation for State Highway andTransportation Officials (AASHTO)in the USA dates back to 1931(Roberts et al, 1996) . Thesespecifications recognised bitumenas a semi-solid and thereforeconsistency measures were usedto develop the Pen-gradingsystem.

In the early 1960s the viscositygrading system was introduced.Testing included penetration at250C, the viscosity at 600C, andthe kinematic viscosity at 1350C.Ageing was also considered andthe thin film oven test was used to

measure relative ageing ofbitumen.In the mid 1980s specificationsgrew exponentially across theUSA, and there were more than 35 different bitumen specifications,which created major problems forbitumen suppliers limited bystorage capacity and localisedmarkets. In 1987 the SHRP wasinitiated to include significantfocus on developing nationaluniform specifications.

While initially it was expected thatthe national bitumen standardswould include compositionalproperties, it was very quicklyfound that only physical properties that describe the visco-elasticnature of bitumen would beincluded. In 1991 the first versionof performance grading systembased on fundamental rheologicalproperties was introduced. It took5 to 6 more years to implementwhat is today the SuperPave PGgrading throughout the USA.

South Africa

The South African bitumenspecifications date back to 1951,with the first publication ofpenetration requirements.Thereafter a revision was made in1966 and the Rolling Thin FilmOven Test (RTFOT) introduced in1972.

Compositional balance

The 1995 SA binder specificationsdid not address compositionalbalance of the bitumen directly.This was a point of concern andsubsequently van Assen and van

135

de Ven (1996) investigated thisaspect and reported on it atCAPS’99. Following therecommendations of a panel ofinternational experts, the BitumenSpecification Task Group agreedon certain changes and rulings:

• That viscosity at 600C be thespecification grading;

• That viscosity at 135 0Cshould include upper limitspecification;

• Low temperature ductilitywas considered important,although the specification of100cm ductility requirementwas considered conservative;

• The minimum Softening Point value after RTFOT andmaximum change value were adopted.

The PG concept linked to thestandard SA specifications

The authors suggest that apotential improvement to thecurrent “bitumen production-based”, rather than performance-based specifications, is the use ofa direct approach in which gradesare based on actual performancefactors at which common criteriaare specified using performance-related properties, similar to theapproach used in the SuperPavespecifications. The difficulty in the direct approach is the need fordirectly measured performance-related properties such as G* andphase angle.

This approach requires expensiveand complex equipment that is out of reach of many pavementengineers. Grades are developedas performance-based in this

approach, and directly related totraffic and pavement conditions.

This is not totally a novelapproach. In the 1980’s the Shellcompany introduced a completepavement design manual based on using Penetration and SofteningPoint and estimating rheologicaland damage resistance propertiesof asphalt mixtures usingnumerical models as given in theShell Handbook (1991).

What is novel in this paper is theuse of the concept to derive aBitumen Performance GradingSystem using the commonlymeasured index properties. In the following section the approach isused to demonstrate how it couldbe implemented for South Africanconditions.

To achieve this it is necessary todefine the models that can beused to derive bitumenconstitutive models based onPenetration and Softening Pointmeasures, i.e. using van der Poel’s nomogrph.

Furthermore, the distribution ofpavement temperatures, such asthe maximum and minimumdesign pavement temperatures,could be taken from weather databases in SA and used to define the performance grades needed forvarious regions in the country.The distribution of maximumpavement temperatures in various regions in South Africa with therange (minimum and maximum)for selected stations in the country was decided upon. Therefore a set of bitumen grades could beselected.

136

Based on discussions withpavement engineers and expertsin SA at a workshop in May 2003,it was decided to work with threemain high temperature grades,PG-52, PG-58, PG-64. To considerhigh traffic volume and/or slowmoving traffic, a PG70 grade could be added. To avoid creating anunmanageable number of gradesand to simplify the system, it isbelieved that a three hightemperature grade system withPG-58, PG-64, and PG70 is a good concise system for South Africa. To cover the low temperaturerange, it can be seen thattemperatures range between -50Cand +80C. It is thereforereasonable to use a system of +6,0.0, and -6.00C. For a fullfactorial system a three hightemperature and a four lowtemperature grid would result in12 grades, which is more thandouble the grades used today inSA. To minimise this multiplicity of grades, a partial system could beused to include 8 grades as shown in rows (1) and (2) of Table 3.

Finally, the performance relatedproperties should be selected andthe acceptable limits foracceptance of bitumen have to bedefined. Following are theproperties selected:

• For workability the viscosity at 1350C as used in thecurrent specifications couldbe used. However, in aperformance specification the

limits should not be changed; they should remain the samefor all grades sincecontractors are expected touse same practice regardlessof the binder source or grade. A range of 0.12 - 0.65 Pacould be recommended based on the ranges listed in thecurrent SA bitumenspecifications (SABS 307-1972 amended in 1997);

• For rutting resistance it isproposed that the penetration and softening point be usedto calculate the PI for thegrades currently used in SA.The PI values are used tocalculate the stiffnessmodulus at speeds of trafficnormally seen in the field (ata typical speed of 60 Km/hr,for a pavement surface layerthickness of 100mm, theloading time is 0.015seconds). The average PI forsuch grade is assumed to be= -0.5 with a softening pointof 540C (40/50 Pen in P658Zone). Using these values in

solving the van der Poelnomograph indicates thatsuch bitumens give a S(0.15) value of approximately 100Kpa. This can then be used in the new specification table for all grades. For higher grades (64 and 70) this stiffnessminimum value should bemet at 640C and at 700Crespectively. Also, to consider the effect of RTFO ageing a

137

The objective is an improvement to the current specification,rather than performance-based specifications

separate row is added toTable 3 to require a minimum stiffness that is 2.5 times theunaged condition;

• For fatigue resistance it isrecommended that averagepavement temperatures beused because fatigue is mostcritical when bitumen isrelatively stiff but subsurfacelayers are not frozen. Infatigue it is assumed thatstiffness should be below acertain maximum value sothat bitumen can deformrepeatedly without damage.To derive stiffness limits, thenomograph published byShell Research (1991) forestimating the fatigue life ofmixtures from the PI ofbitumen and mixture stiffness can be used. A typicalpavement structure isassumed with strain levels of1.0 *10-4 mm/mm for stresscontrolled condition and 5.0*10-4 for strain controlledconditions. Specifying aminimum fatigue life of 1.0*106 cycles, the requiredmixture stiffness isapproximately 3 * 10 9 Pa fora PI value in the range of(-0.5 to 0.0). Using avolume concentration of 13% bitumen in a typicalasphalt mixture, themaximum allowable bitumenstiffness at 0.015 secondloading time should be50,000 kPa. To insure properapplication of this limit the PIvalue of the aged bindershould be less than 0.0. Inthe specification systemshown in Table 3 , the

S(0.015) is limited and alsothe PI value for the PAV aged material;

• For low temperaturecracking the stiffness at 60seconds is estimated attemperatures that are 100Chigher than the minimumgrade temperature. The shift in temperature is used tooffset the effect of shortloading time of 60 seconds as used in the SuperPavespecifications. In addition,the logarithmic creep rate (m (60)) should also becontrolled to minimise stressbuild up in bitumen due tohigh elasticity. Using theproperties of the Pen150-200 and assuming thatthe bitumens of this gradeperformed well in coldclimates in SA, the limits ofS(60) = 400 000 KPa andm(60) = 0.300 could bederived.

Disadvantages of the proposed grading system

Although the proposed gradingsystem shown in Table 3 appearsreasonable and does not dependon using expensive sophisticatedtesting devices, one should notignore some of the importantshortfalls of such a system. These shortfalls could be resolved bygradual replacement of theestimated engineering propertieswith actual measured values using rheometers and extensiometers.

The reasons forthese are thefollowing:

138

• Nomographs are onlyapproximate and showgeneral trends rather thanaccurate values of stiffness or elongation at break;

• The nomographs are basedmostly on conventionalunmodified bitumen. It iswell known that modifiedbitumens are more complexrheologically than

139

1 High temperature grade (HT)

PG 58 PG 64 PG 70

2. Low temperature grade (LT)

-10

-16

-4 -10

-16

+2 -4 -10

Performance relatedproperty

Performancecriteria

For Workability

Viscosity, Pa-s 0.12<h <0.65

For Rutting Resistance

Estimatedcreep stiffness (unaged) @HT, kPa

S(.015) >= 100 58 64 70

Estimatedcreep stiffness (RTFI-Aged,)kPa

S(.015) >= 250 58 64 70

For Fatigue Resistance

Estimatedcreep stiffness(PAV-Aged),kPa

S(.015) <=75000

24 21 30 27 24 39 36 33

Estimated PIvalue(PAV-Aged)

PI > 0.0

For Thermal Cracking Resistance

Estimatedcreep stiffness (PAV-Aged),Kpa

S(60) <= 400 000

0.0 -6 6 0 -6 12 6 0.0

Estimatedcreep rate(PAV-Aged)

M(60) >= 0.310 0.0 -6 6 0 -6 12 6 0.0

Elongation atbreak fromFigure 2(OAV-Aged)

l(60) >= 0.02 0.0 -6 6 0 -6 12 6 0.0

* For slow traffic (10 km/hr), S(.015) limit should be multiplied by a factor of 10

* For high traffic volume, S(.015) limit should be multiplied by a factor of 10

Table 3: Proposed performance grading for South Africa

conventional bitumens andthus these nomographs could be misleading;

• Accumulation of damage andsensitivity of service life totraffic conditions are notdirectly considered and usinga multiplication factor of 10to consider speed or volumeis only an approximation;

• Such system will needcontinuous verification andcalibration to establishpredictability and buildconfidence in estimatedengineering properties.

Recommendations

The paper shows how the Bitumen Test Data Chart (BTDC), and thevan der Poel nomograph, which isbased on penetration andsoftening point, could be used tolink the empirical test results toperformance related propertiessuch as stiffness and strength andhow these derived measures could be linked to traffic volume, trafficspeed and pavement designtemperatures similar to theSuperPave PG system. Theapproach is used to discuss thecurrent South Africa Specificationand to propose a possibleperformance grading system forSouth Africa using actual climaticand traffic data.

It is apparent that there aretangible benefits in using a

performance grading (PG) systemfor binders compared with solelyempirical testing and reliance onexperience for binder selection.The PG system offers:

• A systematic approach totaking account of climate,traffic speed and degree oftraffic loading in the area that the binder is to be used thusminimising subjective andnon-optimal binder selection,and a potentially unifiedapproach for adjudicatingbinders regardless of whether they are unmodified ormodified (although moredevelopmental work isrequired before theSuperpave PG system is fullyfunctional in this respect).

It is possible to establish anindirect PG system without the use of costly binder testing equipmente.g. rheometers etc. However,there are differences between adirect PG system e.g. Superpave,and indirect PG system asproposed in this paper.

Certain assumptions need to bemade to develop the proposedindirect grading system withregard to creep stiffness andelongation at break. It isrecommended that actualmeasured values for suchengineering properties be obtained for the relevant binders usingrheometers.

140

The N7 route between theintersection with the N1and kilometre 18 north of

the intersection (direction ofMalmesbury) neededupgrading to carry thepredicted 9 million 80 kNstandard axle loads over thedesign period. Cracks in thesurfacing showed that wateringress into the base layer was an important reason for thecurrent state of the road. Theexisting base layer consistedof a good quality crushedstone (G2) material, thesubbase layer of a granular G5material and the subgrade ofsandy material (G7).

Due to the fact that the basematerials are of a good quality,cold mix recycling was considereda cost-effective method for therehabilitation of the pavement. Tosave transportation costs of a new base material it was chosen torecycle the top 200-250 mm ofthe pavement in situ with aWirtgen WR-2500.

For the cold-mix recycling twodifferent bituminous binders arefrequently used i.e. bituminousemulsion and foamed bitumen.The two binders have differentcharacteristics and it is dependenton the type of aggregate, themoisture content, the climate,etc., which is the binder of choice.

The quality of the plain G2material is higher than the twoblends. A logical conclusion is tocontinue the research with theplain G2 aggregate mix. For theN7 project, however, it could notbe guaranteed that only G2material would be mixed withoutaccidental addition of G5 material.

Basing the research on the G2material only can therefore resultin conclusions that are tooptimistic. The addition of thecrusher dust showed higherresults than with the addition ofG5, but the difference in strengthis not significant and importingcrusher dust onto the site is

141

Advanced testing for coldrecycling treatment selection on N7 near Cape Town

KJ Jenkins S Robroch MG HendersonUniversity of Delft University Provincial GovernmentStellenbosch Western Cape

J Wilkinson AAA MolenaarJeffares and Green Delft University

The research has shown that for the N7 there is no obviouschoice between bituminous emulsion and foamed bitumen

Extract from CAPSA‘04 paper:

expensive. Therefore, it wasdecided tocontinue the research with theblend of 80% G2 and 20% G5. Triaxial testing was also consid-ered for the G2 + G5 blend. Thisincluded monotonic and dynamictesting. Only the results of themonotonic triaxials are providedbelow, including samples prepared from a trial section.

Conclusions

The research has shown that forthe N7 there is no obvious choice

between bituminous emulsion andfoamed bitumen. Other factors,such as constructability becamedeciding factors. The fieldmoisture content of the granularlayers that were recycled, whichwas close to optimum moisturecontent, dictated that the additionof fluids would have to be limitedto a minimum to ensure thatcompaction was achievablewithout first drying back themixture. This could be bestachieved with foamed bitumenand the rehabilitation projectproceeded with this option rather

142

Figure 3: ITS test results for different aggregate blends

Bitumen Aggregate Cement (%) Bitumen (%) C (MPa) φ(0) R2

Foam Laboratory 1 2.3 0.414 44.2 -

Emulsion Laboratory 1 2.3 0.374 48.4 -

Foam Trial Section 1 1.0 0.420 32.8 0.997

Table 5: Test results monotonic triaxial test

80% G2 + 20% crusher dust

603.8 578.9

381.7461.0

Dry Wet

0

100

200

300

400

500

600

700

Emulsion Foam

Plain G2

583.1

197.2

323.8

224.2

Dry Wet0

100

200

300

400

500

600

700

Emulsion Foam

80% G2 + 20% G5

435.0375.9 262.7

472.3

Dry Wet

0

100

200

300

400

500

600

700

Emulsion Foam

Plain G2 Emulsion Foam Dry (kPa) 603.8 461.0 Wet (kPa) 578.9 381.7 Retained (%) 95.9 82.8 80% G2 20% G5 Emulsion Foam Dry (kPa) 435.0 472.3 Wet (kPa) 375.9 262.7 Retained (%) 86.4 55.6 80% G2 20% Cr Dust Emulsion Foam Dry (kPa) 583.1 224.2 Wet (kPa) 197.2 323.8 Retained 33.8 144.4

than bitumen emulsion. The mixthat was used in the field wasstabilised with 1% cement and2.3% foamed bitumen.

The tensile strength of thematerial (tested with the ITS) isgood, considering the short curingtime. The tensile strength is onlydependent on the moisture.

The cohesion and angle of internal friction results are similar forfoamed bitumen and bitumenemulsion treatment, and becauseof a slightly higher cohesion and aslightly lower angle of internalfriction the foamed bitumen, in

this case, could be expected toexhibit slightly less stressdependency than the bituminousemulsion mix.

The cohesion and angle of internal friction results are similar forfoamed bitumen and bitumenemulsion treatment, wherefoamed bitumen is a little lessstress dependent in proportion tothe bitumen emulsion.

Stabilised cold-mix materialsexhibit stress dependentbehaviour similar to that ofgranular materials.

143

The author claims thatcurrent specification usedin South Africa for the

strength of aggregates forbituminous surface seals isprobably too stringent for lowvolume roads.

South Africa has a large networkof unsealed roads, which carrysignificant traffic and warrant, on

both social and economic grounds, upgrading to sealed standards.Aggregate for surfacing stone iscurrently very tightly specified and as a result, the construction ofconventional bituminoussurfacings is expensive and oftenrequires haulage of suitableaggregate over large distances.

Upgrading of many of ruralunsealed roads can be carried outcost-effectively using marginalbase materials and thin pavementstructures, and it is consideredperhaps unnecessary to use thestandard surfacing stone

specification. The use of marginalsurfacing stone can havesignificant cost savings but itdoes, however, have associatedrisks. Wright et al indicated thatsavings of up to 30% of thesurfacing stone cost and as muchas 7% of the total cost of the sealcan be achieved by using marginal aggregate.

This paper discusses an investiga-tion using the Transportek HeavyVehicle Simulator (HVS) todetermine the impact of usingaggregates softer than specified in chip seals and to propose possiblerelaxations in the currentlyspecified strength requirements.

Background

The investigation made use ofvarious aggregates screened fromnatural materials or prepared bycrushing boulders of appropriatematerials, including a controlsample of crushed quartzite.

144

Aggregate strength forbituminous surfacings for lowvolume roads: a heavy vehiclesimulator (HVS) experience

P Paige-Green CSIR Transportek

Many rural roads can be upgraded cost-effectively usingmarginal base materials and thin pavement structures

Extract from CAPSA‘04 paper:

Relevant aggregate properties aresummarised in Table 1.

The conclusions drawn from thisstudy were:

• For light pavementstructures, a significantrelaxation of the currentaggregate specifications ispossible;

• Depending on the averagedaily heavy traffic, minimum10% FACT values of 80, 100and 150 kN were proposedcompared with the currentminimum specified value of210 kN;

• Rolling of the aggregateduring construction should be

limited to the use ofpneumatic tyred rollers.

It was also clear that for lightlytrafficked roads, limitedbreakdown of surfacing aggregatedoes not necessarily mean failureof the road.

Precautions such as precoating the aggregate, providing a goodpenetrating prime to strengthenthe top of the base, applying a fog spray on top of the aggregate andtrafficking the seal (preferablywith construction trafficimmediately after completion ofconstruction) will improve theperformance of seals withmarginal aggregates.

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Material/Property

Quartz- ite

Sand stone

Crushed calcrete

Screenedcalcrete

Ferri- crete

Chert Ash

10% FACT(kN)

315 100 105 145 42 86 42

10%FACT(wet) (kN)

266 97 85 102 23 64 41

10% FACTratio (w/d)

84 97 81 70 55 74 98

Riedel &Weber value

0.5 0 0.5 0 1 0.5 0

Bulk relative density

2.8 2.58 2.54 2.53 2.32 2.42 1.84

Apparentrelativedensity

2.82 2.67 2.72 2.72 2.95 2.95 2.3

Waterabsorption(%)

0.2 1.2 2.6 2.7 9.2 3.9 10.9

Flakinessindex (%)

22.7 25.2 7.7 5.5 3.6 9.7 16.4

Averageleastdimension(mm)

9.8 6.9 7.9 8.3 7.7 7.7 6.6

Table 1: Summary of selected material properties

The following materials were usedin the HVS test trials:

• Quartzite (control);• Screened calcrete;• Screened chert;• Screened sandstone.

Sections were also constructedusing pre-coated material toevaluate the effect of pre-coatingon the actual performance of themarginal materials tested. Thefollowing materials were used:

• Pre-coated screened calcrete;• Pre-coated screened chert;• Pre-coated screened

sandstone.

In addition, a sample of crushedsilcrete from Botswana was tested. This material had a dry 10% FACTof 265 kN and a wet value of 165 kN. The wet-dry ratio wasthus only 63%, classifying this asa marginal aggregate in terms oftraditional specifications.

Based on a small-scale laboratoryand field investigation using theHVS, the author proposes arelaxation of aggregate strengthspecifications for lightly traffickedroads as shown in the blue boxbelow:

Precoating of the low strengthaggregates results in a significantimprovement in theirperformance. It should be noted, however, thatthe HVS could not simulateparticle whip-off by faster traffic,particularly of crushed aggregateparticles. While this is recognisedas an unavoidable deficiency inthe experiment, close observationof the test panels indicated thatvoids were not formed in the seal.For lightly trafficked roads, treated periodically with a fog spray, it isconsidered that low strengthaggregates can be successfullyutilised.

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<3 heavy vehicles per day - 10% FACT 80 kN 3 - 6 heavy vehicle per day - 10% FACT 100 kN 6 heavy vehicles per day - 10% FACT 150 kN

In recent years, much of the Gauteng Heavy VehicleSimulator (HVS) related

research has focussed onfoamed bitumen andemulsified bitumen treatedmaterials (FBTMs and EBTMs),with specific emphasis ondeveloping structural designmodels for incorporation intothe South African Mechanistic-empirical Pavement DesignMethod (Theyse, 2000).

This paper discusses the typicalbehaviour of FBTMs and EBTMsand selects appropriate transferfunctions based on this behaviour. The development of transferfunctions for these materials isdiscussed, detailing the data setsused, the analyses procedures and the enhancements made to theprocedures and models asprogress was made. The transferfunctions developed to date arepresented and the limitationsthereof discussed.

It must be noted that these arenot the only HVS tests on EBTMs,but they are the only tests forwhich the complete set ofnecessary laboratory and HVSdata were collected. In all theabove sections, multi-depth

deflectometers (MDDs) wereinstalled to collect information onelastic deflections under a load,and the permanent deformation at various depths in the pavement.

These data are used extensively in the analyses. On all the HVSsections included above, at leasttwo HVS sections were tested ateach test location. The testsinclude a test using a 40 kN wheel load (E80 axle load) and anothertest at a higher load. All the HVSdata are detailed and analysed inthe references given. Behaviour observed under theHVS

The typical behaviour observed inthe early stages of an HVS test isthat the resilient modulus of thetreated base layer starts of at arelatively high value and thendecreases under the action oftraffic until a constant resilientmodulus is reached. This occursrelatively early in the life of thepavement, and can occur rapidlyunder heavy traffic loading.

The constant modulus reached istypically similar to the modulus ofthe untreated parent material andhas been referred to as the

147

Mechanistic-empirical structural design models for foamedbitumen and bitumen treatedmaterials

F Long H TheyseCSIR Transportek CSIR Transportek

Extract from CAPSA‘04 paper:

“equivalent granular state”. Thisterm is somewhat misleadingbecause the material is equivalentin resilient modulus only, and notin the condition of the material,i.e., the treated material is not in

a loose, particulate state. Toreduce the confusion, this“equivalent granular state” will bereferred to as the “constantstiffness state”.

Strain-at-break test The strain-at-break test is afour-point monotonically loadedflexural beam test that measuresthe flexibility and tensile strengthof treated materials (Theyse,2000). The flexibility is measuredby the strain-at-break and thetensile strength is measured bythe stress-at-break. The test wasperformed on all the materials

used to develop the transferfunctions. The effect ofcompaction and moisture regimewas also by means of monotonictriaxial tests, as shown in Figure4.

a) Phase 1 (stiffnessreduction) life as a function ofthe strain ratio

The duration of Phase 1 and strain ratios are plotted in Figure 6 forthe three sets of materials. Toobtain the fatigue life transferfunction, a log-linear model of theform shown in Equation is fit tothe data, as illustrated by thethree straight lines in the Figure.

Nef = a(SRε)b

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No cement, 2.25% binder1% cement, 1.5 % binder1% cement, 2.25 % binder1% cement, 3.0% binder2% cement, 2.5% binder

Low saturation,low relative

density

Low saturation,high relative

density

High saturation,low relative

density

High saturation,high relative

density

Untreated

0

1000

2000

3000

4000

5000

6000

Figure 4: Maximum allowable principal stress at various combinations

b) Permanent deformationtransfer function:

Permanent deformation transferfunctions were developed

separately for foamed bitumenand emulsion materials.

A log-cubic model was used asshown in Figure 8.

149

Strain Ratio

Emulsion dataEmulsionPG243/1 TG2 dataTG2 FTBMN7 FTBMN7 FTBM data

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

Figure 6: Phase 1 (stiffness reduction) life transfer functions

P243/1Cullinan, BETM, 100mmCullinan, BETM, 150mm1% cement, 3% binder2% cement, 1.8% binder1% cement, 0.9% binder1% cement, 1.5% binder

Stress Ratio

0.5 0.6 0.7 0.8 0.9 1.0 1.20.40.30.20.10.01.0E+ 04

1.0E+ 05

1.0E+ 06

1.0E+07

1.0E+ 08

1.0E+09

1.0E+ 10

Figure 8: Laboratory predicted and HVS structural capacities for EBTMs(17% plastic strain)

A comparison of predictionsdeveloped from this data is shownin Figure 9.

Conclusions

This paper describes the use ofHVS and laboratory data todevelop mechanistic-empiricalstructural design models forfoamed bitumen and emulsifiedbitumen treated materials. Twotypes of transfer functions aredeveloped to capture thetwo-phase behaviour of these

treated materials, firstly, areduction in modulus, andsecondly, permanent deformation.

Transfer functions have beendeveloped over the last few yearsin an incremental manner, and the paper describes the proceduresused to develop the transferfunctions and discusses anychanges made to the proceduresduring the analyses. The paperattempts to highlight the continual improvements made to theanalysis techniques, whichimprove the final results.

150

1.0E+05

1.0E+05

1.0E+ 06

1.0E+ 07

1.0E+ 08

1.0E+ 04

1.0E+ 09

1.0E+ 10

1.0E+101.0E+091.0E+ 081.0E+ 071.0E+06

HVS predicted

1:1416A5: MDD8416A5: MDD4

415A5: MDD8415A5: MDD4

415A5: MDD12

Figure 9: Comparison of laboratory and HVS permanent deformationfor treated materials

Traditionally the contractor is required to develop anasphalt mix design that

complies with specificempirical and or performancerelated criteria. However, ithas been found thatcompliance with these designcriteria, does not necessarilyguarantee future performanceof the asphalt mix.

This is specifically a problemwhere it concerns resistance todeformation and distress due towet trafficking. The engineer isfaced with the dilemma that newmix compositions (or designs) can

only be assessed after havingbeen exposed to traffic loadingover a period of time. For thisreason, the specification calls forrut resistance tests to beperformed as a final check beforethe mix can be approved. Thispaper discusses a case study inwhich accelerated pavementtesting (APT) using the modelmobile load simulator (MMLS3),was used to address this problem(ITT,2003).

Asphalt surfacing and base coursetrials for rehabilitation of the 03 -21R runway of JohannesburgInternational Airport, wereconstructed with approval of theengineer, after complying with alllaboratory test criteria.

Subsequently, rutting performance of the mixes proved to be suspectunder MMLS3 field trafficking.Gyratory compaction and dynamiccreep performances did not predict excessive deformation under theMMLS3 trafficking.

Several studies served asbenchmarks for the interpretation

of the results of ruttingperformance under MMLS3trafficking. In two extensivestudies (Smit et al, 2003, MartinEpps et al 2002, and Walubita et al, 2002), the relationshipbetween truck trafficking andMMLS3 trafficking wasinvestigated. It was shown that itis reasonable to relate the ruttingperformance of the respectivetrafficking systems on aone-to-one basis, provided

151

Rehabilitation of runway atJohannesburg InternationalAirport: selection of asphaltmixes using MMLS3 testingP Molenaar F Hugo J Beukes G CatinStewart Scott Institute for Transport Much Asphalt Rand Roads Technology

The use of HVS and laboratory data to develop mechanistic-empirical structural design models

Extract from CAPSA‘04 paper:

temperature, load frequency,wheel path wandering, andeffective traffic volume is takeninto account. It was also shownthat extrapolation of the ruttingresults after the application of100,000 or 200,000 MMLS3 axlesgives a very good estimation ofthe ultimate rutting of thepavement after 1 million MMLS3axles.

These findings were used to draftthe following interim ruttingprotocols that are currently beingused to evaluate ruttingperformance of asphalt under dryand wet heated trafficking with the MMLS3:

• The rutting performance canbe analysed fundamentally by considering vertical stressprofiles under the respectivewheels are used for purposeof comparison. The limitingrut depth has to bedetermined in terms ofexpected traffic, lateralwander, lateral load wanderand load frequency, climaticconditions during life cycle,tyre pressure and layerthickness;

• The following are generalguidelines for field ruttingperformance at criticaltemperature (generally 500Cor more) and 7200 loadapplications per hour are:• <3mm after 100 000

MMLS3 load applicationson highways; and

• <1.8mm after 100000MMLS3 load applicationson airports.

• For determining moisturesusceptibility of asphaltpavements using wettrafficking after 100 000applications at 500C heatedwet MMLS3 axles: • SCB residual strength of

hot mix asphalt 80%;• SASW residual stiffness

(Lee et al, 1997) 80%;and

• SCB fatigue ratio 50% forhot-mix asphalt.

• Composite pavements require special consideration toevaluate entrapment ofwater;

• Critical temperatureconditions are determinedfrom the hottest seven (7)period according to SHRPManual 648A (Huber 1994)with due regard to the localstudy reported by Everitt et al (1999).

In order to estimate full scalerutting from scaled MMLS3 tests,certain adjustments need to bemade. These include:

• Adjustment for stressdistribution under the smaller surface contact area of theMMLS3 wheel (divide by 0.4to 0.45);

• Adaptation for geometry oftest set-up, whether in thelaboratory or in the field (seeTable 7 below) (multiply byfactor);

• Adjustment for lateral wander in real life versus channelised MMS3 tests (multiply by 0.6).

If all the above factors are takeninto account, the effective

152

downward rut due to thedeformation of the upper 95 mmafter ten years of trafficking istheoretically estimated as set outin Table 8.

Laboratory MMLS tests

During construction it was noticedthat the rutting of two sections ofnewly completed runway,manifested different early rutting.

In the region of the southernthreshold, the surface had ruttedabout 3mm under traffic ofdeparting aircraft while the rut700m to the north was about7-8mm deep.MMLS tests on cores from thesesections yielded the results shownin Table 9.

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Material type Field trafficked in situ

Laboratorytrafficked cores

Laboratorytraffickedbriquettes

Surfacing layer 1.25 1 -1.2 1

Base layer 1.3 1 -

1.55 1Composite layer:Surfacing + Base

1.27 (estimate) 1 -

Table 7: Relative rutting relationship between various modes of trafficking

Downward rut ofsurface layer (test 10)

(0.6 X 1.25 X 5.5mm)/0.45 = 9.2mm

Plus: Downward rut ofbase layer (test 5)

(0.6 X 1.55 X 1.3 X 2.8mm)/0.41 = 8.3mm

Estimated total downward rut = 17.5mm

Table 8: Analytical calculation of downward rut of upper 95mm of HMA

Ch 725 Downward rut ofsurfacing and basecomposite as-built layers

(0.6 X 1.27 X 3.5mm)/0.30 = 8.9mm

Ch225 Downward rut ofsurfacing and basecomposite as-built layers

(O.6 X 1.27 X 1.8mm)/0.30 = 4.6mm

Table 9: Estimated theoretical rut depth of composite surfacing and base layerunder aircraft loading

Conclusions

From the results of the testedcores and the related ruttingperformance under MMLS3trafficking, it was possible toestablish the extent to whichsections were susceptible todistress due to trafficking. Thenature of the procedure is suchthat it provides a basis for takingaccount of climatic conditionsduring the life cycle of thepavement through a rationalapproach.

Overall, the procedure providesconfidence in determininglong-term performancecharacteristics of an asphalt mixeven before the paving trial hasbeen performed. The constructedrutting performance findingsappear to indicate that the general protocol for limiting field rutting

for aircraft may be slightlyconservative. However, this isdependent on the relationshipbetween core and fieldperformance. It should thereforebe retained until currently usedrelationships are further validated.The successful application of theMMLS3 design procedure is a basis for enhanced performanceprediction of asphalt mixes.

This should result in measurableeconomic benefits. In this regardit would be prudent to implementa modest system of long termmonitoring of the level of thepavement surface and theunderlying base course at anumber of cross sections of therunway. This will serve to increase confidence in the use of theMMLS3 system and the relatedperformance protocols.

154

This paper compares thestrength parameters andoptimum foamed bitumen

contents of foamed bitumentreated materials. Correlationsbetween Indirect TensileStrength (ITS) and Unconfined Compressive Strength (UCS) of 100 mm and 150 mm diameter briquettes are established for23 samples treated withvarying quantities of foamedbitumen and cement/lime.

The samples were taken fromthree different project sites inSouth Africa and Greece. Optimum foamed bitumen contents derivedfrom the different strengthparameters are compared and thetreated materials are classifiedbased on the correlationsestablished.

Results indicate that the currentuse of UCS as a primaryparameter for treated materialclassification and the use of thesoaked 150 mm ITS as anindicator of treated materialmoisture sensitivity is not

necessary. The results highlightinadequacies in the currentmaterial classification system. Background

In the past, 100 mm diameter(Marshall) briquettes were usedfor mix design and field qualitycontrol for foamed bitumentreated materials (Lewis et al,1995). The ITS was used as anindicator of relative strength in the

dry state and as an indicator ofmoisture sensitivity in the soakedstate.

Subsequent research led to therelease of Interim TechnicalGuidelines: The design and use offoamed bitumen treated materials, TG2 (Asphalt Academy, 2002).The mix design procedure in TG2is more extensive than was usedpreviously, and 150 mm ratherthan 100 mm diameter specimensare used.

The TG2 guideline classifiesfoamed bitumen treated materials

155

Correlations between differentITS and UCS test protocols forfoamed bitumen treatedmaterials

M Houston F LongLoudon International CSIR Transportek

It is redundant to use both the UCS and ITS tests

Extract from CAPSA‘04 paper:

according to ITS and UCS on 150mm diameter briquettescompacted at 100% ModifiedAASHTO compaction. Based on the treated material classification,structural design calculations could be made. The motivation for theuse of both the UCS and ITS wasto capture both the compressivestrength and the flexibility of themix.

Briquette preparation

100mm diameter briquettes:

The 100mm diameter briquetteswere prepared in accordance withpast practice (Lewis et al, 1995).This method was adapted from the Marshall method (for asphalt) with modifications to the compactiontemperature and curingprocedures. Soaked briquetteswere subjected to 24 hours inwater at 400C as opposed tosoaking under a vacuum for 1hour.

The properties and moistureregimes tested included:

• Dry ITS (ITSdry100).Briquettes were cured at400C for 72 hours. Thisprocedure dried the briquette out to less than 1% moisturecontent without excessivelysoftening the bitumen;

• Soaked ITS (ITSwet100). Dry briquettes were soaked inwater for 24 hours atambient temperature(approximately 250C).

150mm diameter briquettes

The 150mm diameter briquetteswere prepared in accordance withTG2 (Asphalt Academy, 2002).The properties and moistureregimes tested included:

• ITS at equilibrium moisturecontent (ITSeq150).Briquettes were allowed tostand unsealed at ambienttemperature for 24 hours and then 48 hours in a sealedplastic bag at 400 C. Themoisture content using thismethod is aimed atsimulating field equilibriummoisture. The cured moisture contents were a function ofthe compaction moisturecontent (which varied fromsample to sample) andmaterial type; they werefound to be between 2.5 and6%;

• Soaked ITS (ITSwet150).Briquettes cured toequilibrium moisture contentwere soaked in water for 24hours at ambienttemperature (approximately250C);

• The UCS tests wereperformed at equilibriummoisture content, i.e. thesame curing procedures asthe ITSeq150 briquettes were followed.

ITS and UCS Relationships

From the investigations it wasapparent that correlations couldbe established between many ofthe variables tested, with varyingdegrees of fit.

156

Conclusions

The following conclusions andrecommendations are made:

• A FB1 treated material can be classified with 100 mmdiameter briquettes with areasonable level ofconfidence. All other material classes can be derived fromthe ITSdry100, but with a lowlevel of confidence. It istherefore recommended that150 mm diameter briquettesbe used for mix design andmaterial classifications, andfor field quality control;

• ITSeq150 can be used to derive UCS and ITS150wet. It canalso be used, on its own, todetermine the optimumfoamed bitumen content;

• The ITSwet150 tests show agood correlation with theITSeq150. This maydemonstrate either that theITSwet150 is not a goodindicator of the moisture

sensitivity of a mix or thatITSeq150 is a satisfactoryindicator of moisturesensitivity. It is not possiblefrom these data to determine which statement is morecorrect. It is recommendedthat an alternative test formoisture sensitivity beinvestigated;

• The mix design proceduresand classification system offoamed bitumen treatedmaterial contained in TG2should be revised, as it isredundant to use both theUCS and ITS tests. A testthat actually measures theflexibility of a material, suchas the strain-at-break four-point beam test, shouldbe investigated further forpossible use in the materialclassification;

• Use of either the UCS or ITSin the mix design procedureshould be sufficient fordetermining the optimumbinder content.

157

Figure 3: ITSdry100 versus ITS eq150

158

Figure 7. ITSeq150 versus ITSwet150

Figure 9. UCS versus ITSwet150

Heavy vehicle overloadingcontinues to be a majorproblem in South Africa

despite efforts at moreeffective overload control bythe authorities. Overloadingcauses premature roaddeterioration and, togetherwith poor vehicle maintenanceand driver fatigue, contributessignificantly to South Africa’spoor road safety record.

One of the tasks of theDepartment of Transport’sNational Overload Control Strategy was to investigate the possibilityof implementing some form ofself-regulation in the heavyvehicle transport industry.

An international review found thatthe National Heavy VehicleAccreditation Scheme (NHVAS)that has been implemented inAustralia over the past few yearshas a number of componentsappropriate to the South Africansituation. The aim of the initiativeis to increase the responsibility of

the transport operator and/orconsignor/consignee for loadingvehicles correctly, therebyreducing the occurrence ofoverloading and under-loading.The self-regulation initiative wasdeveloped and implemented asthe NHVAS and covered twodistinct modules: mass manage-ment and maintenancemanagement. A third module forfatigue management is likely to be launched during 2004.

The NHVAS allows heavy vehicleoperators to demonstrate, through audit of their transport manage-ment systems and vehicle ordriver assessments that theirvehicles and drivers comply with

regulatory standards.

In reviewing the Australianscheme, which extends beyondvehicle mass/overload control tothe crucial safety issues of vehiclecondition and driver fatigue, it was clear that the fundamentals arewell-grounded and that the

159

A self-regulation initiative toaddress the heavy vehicleoverloading problem inSouth Africa

PA Nordengen F OberholzerCSIR Transportek Forest Engineering

The aim of the initiative is to increase the responsibility of thetransport operator and/or consignor for correct loading

Extract from CAPSA‘04 paper:

scheme was developed with inputfrom a wide range of stakeholders.

The paper describes an initiative in the timber industry which resulted in a pilot project, initially fundedby the Department of Trade andIndustry (DTI) and Forestry SouthAfrica under the DTI’s SectorPartnership Fund (SPF). Theproject commenced in August2003 and to date a number ofaspects have been addressed, allof which have involvedconsultation with representativesof the timber industry and otherrole players:

• Underlying principles andbusiness rules;

• Rules of compliance foraccreditation;

• Proposedincentives/concessions foraccredited operators;

• Heavy vehicle managementsystem incorporating vehicleloading, vehicle maintenance, load safety and driverwellness;

• Monitoring of vehiclecombination masses atdestinations (pulp mills);

• Implementation plan(Application, pre-accreditation andaccreditation phases);

• Development of trainingmodules;

• Training workshops for senior management;

• Meetings with theKwaZulu-Natal Department of Transport, MpumalangaProvincial Government andTRAC (N4 Maputo corridorconcessionaires).

The project is essentially driven by the private sector withinvolvement and support fromgovernment. It is viewed as aproactive response to theimpending amendments to theRoad Traffic Act such as extending the responsibility of overloading to the consignor and/or consigneeand the introduction of a roaddamage “fee” over and abovefines for overloading.

Vehicle load monitoring

An important aspect of the project is the load monitoring that is done (in the case of the timber project)at the consignee weighbridges.Currently, only the total vehicle orcombination mass and not theindividual axle and axle unitmasses are measured andmonitored. The weighbridge datais made available to the projectteam, allowing the monitoring ofoverloading and under-loading byoperator and by mill. This enablesa certain amount of benchmarking to be done and reporting on bestand worst practice in the industry.

The tare masses of the variousvehicle combinations are alsomonitored, again giving anindication of best practice. Forexample, the tare mass ofseven-axle vehicle combinations(1222) used for transportingtimber has reduced fromapproximately 27 tons in 1992 toless than 17 tons in 2002. Thishas resulted in an increase in thelegal payload of 34%.

Although not considered as one ofthe rules of compliance, a

160

prerequisite for becoming anaccredited operator is that 96% of all vehicle/combination massesmust fall within the legal load plusthe tolerance for a minimum ofthree consecutive months.Opinions have been expressedthat allowing 4% of vehicle trips to be prosecutable (more than 5%overloaded) is unacceptable.

However, a pragmatic approachhas been adopted initially. In anyevent, an improvement by anindividual operator from 40% (oras much as 100%) of vehicle tripsbeing prosecutable to less than 4% is a significant improvement!These statistics would never beobserved at provincialweighbridges, as in most casesless than 5% of all overloadedvehicles are weighed at provincial

weighbridges and in addition,there are numerous routes in thecountry where no overload controlis done at all.

Phases of accreditation

Three phases of accreditation have been defined as part of the pilotproject:

• Application: During theapplication phase, thetransport operator is required to attend a LoadAccreditation Programme(LAP) training workshop(where the Heavy VehicleLoad Management Systemmanual is distributed) and

commence with meeting therequirements of the rules of compliance. In the case of“mass” industries, monitoring of the vehicle loads either atthe origin or destinationwould commence. At thisstage the prerequisite foradvancing to thepre-accreditation phase is toachieve a minimum of 96%of vehicle combinationmasses complying with thelegal load plus the 5%tolerance for threeconsecutive months;

• Pre-accreditation: At this

stage of the project the LAPsteering committee conductsan audit once the transportoperators indicates that he isready for an external audit.

In some cases, where not allthe requirements have beenmet, one or more follow-upaudits are required. To date,three transport operatorshave been pre-accredited;

• Accreditation: Operatorswill be awarded full accre-ditation once the system hasbeen implemented throughthe South African NationalAccreditation System(SANAS). Audits (andcertification) will then becarried out by SANAS-approved accreditationbodies. Monitoring of thevehicle loads will continueduring the accreditation

161

The success of the project is to a great extent due to the activeinvolvement of the consignees and consignors

phase. Annual audits will berequired by an auditor from a SANAS-approvedaccreditation firm.

Conclusions

Since vehicle monitoringcommenced in November 2002,the incidence of prosecutablevehicle overloading (overloadsgreater than 5%) in the timberindustry has reduced by 24% (asof June 2004). Furthermore, theaverage overload per vehicle hasreduced by 14% during the sameperiod. These figures areimpressive, particularly as onlythree transport operators havebeen accredited to date. Othersare in the application phase,preparing for an external audit.

The success of the project is to agreat extent due to the activeinvolvement of the consignees and consignors. At certain mills apenalty has been introduced which is applied to any vehicle thatarrives at the mill and is found tobe more than 5% overloaded ontotal vehicle mass. At these mills,improvements of more than 80%in terms of incidence of vehicleoverloading have been observed.

The enactment of the pendinglegislation regarding theresponsibility of the consignorand/or consignee in terms ofensuring that vehicles are legallyloaded is likely to add significantmomentum to the LAP initiative.

162

Ninham-Shand ad here

163

165

Member

contributions

U ltra thin friction courses(UTFCs) are specialisedasphalt wearing courses,

designed specifically ascost-effective surfacing orre-sealing layers, withenhanced long-term surfacetexture and sealing properties. Worldwide, these thinsurfacing types are typicallydeveloped as proprietaryproducts designed forspecialised application.

The authors have undertakencomprehensive market researchinto the development of a range of application differentiated UTFCs,each tailor-designed for specific

southern African applications. This work was done for ZebraBituminous Surfacing as part of aproduct development initiative. Itwas found that this type ofsurfacing offers greater:

• skid resistance;• road noise reduction;• spray reduction; and

• surface sealing over the fulldesign life at cost-effectiverates compared toconventional alternatives.

The strict performance criteriadeveloped for these specialisedproducts, and the binder andsealing membrane durabilityaspects, were thoroughly testedand analysed. Various case studies on the design and performancetesting and product selectionprocess were undertaken inconjunction with and theProvincial Government’s WesternCape Road Branch, including theN7 resurfacing contract betweenCape Town and Malmesbury.

Need for UTFCs in southernAfrica

The road user and the roadauthority have different needs and expectations concerning theperformance of road surfacings,especially in developing countries,where the road authorities budgetconstraints are generally high.

167

Specialised ultra-thin asphaltfriction courses for southernAfrica

FJ Pretorius JC WiseArcus Gibb Consultants Zebra Bituminous Surfacing

User requirements focus on safety and comfort, while the roadauthority requires low cost and long-term durability

User requirements focus on safetyand comfort while the roadauthority requires low cost andlong-term durability. Thistranslates into a complex series ofengineering properties to beaddressed by the road designer,including:

• adequate low speed and highspeed skid resistance;

• low noise production fromvehicle tyres;

• smooth ride;• minimal spray;• good visibility of markings;

and • low construction and

maintenance costs.

The concept of ‘separation of layer functions’ argues that structurallayers can meet the load bearingcapacity of the pavement, whilethe surfacing layer design can

meet road-engineeringrequirements. This concept hasgiven rise to the new class of thinand ultra-thin surfacings.

Definition and characteristics

UTFC’s are technically defined as a special group of open to gap-graded asphalt mixes whichgenerally have less than 25% ofaggregates passing the 2.36mmsieve and the remainder of theaggregate consisting of a singlesize stone (6.7 mm, 9.5 mm or13.2 mm). UTFCs are less opengraded than Open-Graded Asphalt(OGA) mixes with:

• 12-19% Voids In Mix (Vim’s)against the 20-30% ofOGA’s;

• 22- 30% Field Voids against28-35% of OGA’s.

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Figure 1

COLTO Med. (5% vims)SMA (5% vims)

UTFC (16% vims)

Open Graded (25% vims)

Sieve size

0.01 0.1 1.0 10 1000

20

40

60

80

100

They also have greater long-termdurability and design life thanOGA’s. A modified tack sprayprocess is used to ensure excellent adhesion to the “base” anddurable waterproofing of theinterface. Thickness varies from15mm to 22mm depending on themaximum stone size used. Arough comparison of gradings forContinuously Graded, SMA, UTFCand Open Graded mixes is shownin Figure 1.

Case study: N7 Cape Town

UTFC Mix optimisation study:Various high performance UTFCmix designs were evaluated withperformance simulation testing toderive optimum mixes for use onthe N7 resurfacing contractbetween Cape Town andMalmesbury. The design trafficwas eight million equivalent 80kNaxle loads and the major designrequirements on this high-speedrural highway were:

• Long-term friction/skidresistance; Low spraygeneration;

• Low rutting potential andhigh durability to last 12 to15 years.

External noise reduction was notan essential requirement.

The preferred layer propertiesrequired were therefore:

• High initial (2.0mm) andend-of life (1.5mm) surfacetexture;

• High interconnected fieldvoids (16 initially, 12 at endof life);

• High durability (film thickness 10.5 micron; Cantabro) toensure a 12 year life;

• High aggregate polishresistance (PSV 48).

Three UTFC mixes (a 13.2mm mixand two 9.5mm mixes, one ofwhich contained more cubicalaggregate) were evaluated, eachat two binder contents, to identifythe optimal mix.

Observations:

• The texture depths andinterconnected voids of the13.2mm mixes wereconsistently higher over thefull loading spectrum;

• The visual end condition ofthe 13mm mixes, especiallyon the higher bindercontents, confirmed theirsuperior characteristicscompared to the 9.5mmmixes.;

• The 13mm mixes alsoshowed 50% less rutting(2.5mm after 100 000simulated loadings) than thebest of the 9.5mm mixes (3.5 - 4.0mm rutting);

• The pendulum friction testand field tests with the GripTester at 50km/h and80km/h confirmed theexcellent friction properties of all three mixes with the13.2mm mix again standingout as the best;

• Based on the main selectioncriteria - surface texture andinterconnected voids to beoptimal over the fullfunctional life - the 13.2mmmix was identified as thepreferred mix;

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• All mixes satisfied the ruttingresistance criteria (less than3.5mm at 100,000 MMLSrepetitions);

• The 9.5mm mix, with the less cubical aggregate, was thesecond best mix due to itshigher durability and filmthickness compared to theother 9.5mm mix. However,this mix was only recommen- ded for areas of trafficloading lower than 7 millionE80’s.

Conclusions

The study concluded that theseUTFC’s offer better all-round andlong-term functional propertiesthan Coarse Graded Asphalt(CGA), Stone Mastic Asphalt(SMA) and Surfacing Seals. Theyare comparable to, and in somecases less expensive than theconventional alternatives,especially if the accident costsaving aspect is discounted.

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In the March 2003 editionof the Sabita Digest therewas an article on the

historical development of thepre-fabricated, bitumen-rubber bound road patchdeveloped by AJ Broom RoadProducts (Pty) Ltd.

To fully appreciate the many advantages ofprefabricated products for road maintenanceit is important tobreak down theoperation of repairusing conven- tionalhot or cold pre-mixedasphalt for routine and emergency roadmaintenance.

In the case of apothole, the crew willexcavate all poorquality surface andbase material as wellas increase the area of the excavation. This is necessaryto accommodate the compactionmachinery needed to compact thebase-course material that isback-filled to a level between20mm and 50mm below the topsurface of the surrounding wearing course.

Furthermore it is necessary to cutthe edges of the excavated areasquare to accommodatecompaction against the edges ofthe excavation.

These details are shown in Figure1.

All of these operations are timeconsuming and in most casesresult in a larger area than isnecessary being repaired.With a pre-fabricated product it isnot necessary to cut theexcavation larger than the failure,nor is it necessary to square cut

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Pre-fabricated road patches forroutine and emergency roadmaintenance

M ChurchAJ Broom Road Products (Pty) Ltd

Figure 1

the edges because the pot hole isfilled to the same level as thesurface of the top of the wearingcourse, and the road patch applied over the backfilled area.

Details of the pre-fabricatedmethod of pothole repair areshown in Figure 2.

For a comparison of theproductivity of the two methodsrefer to Figure 3.

These factors do not take into accountwastage of materials which can be ashigh as 35% withhot or coldpre-mixed asphalts,but nil withpre-fabricatedproducts.There are similarbut greaterdifferences in thecomparison between the utilisation ofconventional and

pre-fabricatedmaterials for repairsto crocodile cracking.The most profounddifference is that withpre-mixed asphalt it is necessary to excavate in a similar method to that described underpothole repairs above, whilst with a pre-fabricated road patchthe product may beapplied directly on top of the cracked area to reseal the wearingcourse. This is solelydependant on there

not being considerabledeformation and/or rutting.

Figure 4 shows the productivitycomparison for the two methodsof surface treatment.Emergency repairs necessarybecause of mechanical damage tothe road structure caused byaccidents, floods, etc. are bothswift and simple to undertakeanywhere and at anytime due to

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Figure 2

Figure 3: BRP productivity factors for roadmaintenance activities

the pre-fabricatedproducts’ ambienttemperatureinstallation withoutexpensive orcomplicated tools.The absence of alimiting storage lifemakes the productalways available.

Many moreauthorities insouthern Africa,Africa and overseasare seeing thebenefits bothtechnical and economic ofpre-fabricated products andsubsequently are specifying andusing greater volumes annually.These road maintenanceauthorities have accepted thatproducts should not be boughtprimarily on price but oncomparison of the cost of variousrepair processes wherein differentproducts are utilised.

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Figure 4BRP productivity factors for roadmaintenance activities

Colas Namibia hasdeveloped a new andinnovative

bitumen-emulsion basedtechnology to solve one ofNamibia’s most persistent road maintenance problems.

Faced with recurring damage tothe edges of roads throughout thecountry — damage whichprogressively narrowed the usable width of surfaced roads, forcedheavy vehicles to travel partiallyon the shoulders when facingoncoming traffic, and impactednegatively on general road safety— the Namibian Road Authoritysought a cost-effectiverehabilitation measure which was

both possible within the budgetconstraints of the NamibianDepartment of Transport, andwhich made optimum use ofscarce physical resources.

A system was developed using acoarse-graded emulsion basedslurry mixture applied by acontinuous-mixing slurry machinefitted with a special spreader box.Using this system, the company

has now completed more than 175 km of edge-widening on a sectionof Trunk Road 1 betweenRehoboth and Mariental.

Background

“Damage to the edge of abituminous surfacing becomes amajor maintenance problemespecially if the seal width isnarrow,” according to Mr Ako Jaf,a regional engineer in the formerNamibian Department ofTransport. “Traditional wideningof the pavement with theplacement of narrow but deeppavement layers is difficult andcostly to construct, with the added difficulty of achieving adequate

compaction using small plant. This invariably results in a pos-compaction edge drop, itself asafety problem, and leads topremature failure of the wideningand adjacent in situ pavement.

“The Namibian Road Authority isfaced with this problem on manyof its routes in the less populatedareas. The road between Rehoboth and Mariental, which forms part of

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The use of bituminous slurry forshoulder protection

T DistinColas SA (Pty) Ltd

The narrowing of the surfaced road caused a confined feeling,with heavy vehicles tending to straddle the centre line

the main North-South arterialroute, carries up to 700 vehiclesper day 20% of these being heavy vehicles. Although the originalbituminous surfacing had beenconstructed to a width of 6.2 m,ongoing edge-break has reducedthis surfacing to just 5.8 m insome places. This resulted in anunsafe road with highmaintenance costs due to theongoing edge-break repairs. Thenarrowing of the surfaced roadalso caused a confined feelingwhen travelling at 120 km/h, withheavy vehicles tending to straddlethe centre- line of the road,’’ saidJaf.

Given the level of traffic, therecommended level of servicerequired a minimum lane width of

at least 3.4m. This meant that the road required widening of at least300 mm on both sides.

After investigation, their roadmaintenance company and slurryapplicator developed a cost-effective solution to widen theexisting bituminous seal.

The traditional method of repairing the damaged edge was done bycutting the broken surface andexcavating the shoulder gravel toallow the placement of a new layer of gravel which was surfaced withcold-mix asphalt. Besides beingvery expensive and timeconsuming this method suffersfrom the following drawbacks:

• Uses large quantities ofgravel —a scare resource which needed to be hauledlong distances;

• Difficult to construct andachieve proper compaction of the narrow strip with smallplant;

• Failure and/or postcompaction at the joint of the newly placed material andexisting surface;

• Lengthy construction periodsresulting in longer trafficdelays.

These problems dictated a morecost- effective and efficientmethod which would render afit-for- purpose remedialtreatment within the limitedbudget constraints of the

Namibian Department ofTransport.

“The initiative was taken in 1998when I was regional engineerresponsible for this section ofroad,” Jaf said, “and I approachedMr Johann Essmann of ColasNamibia (formerly Road Binders)to develop a non-traditionalsolution for widening thesurfacing. The desired outcome ofour investigation was to find alow-cost treatment, which wouldperform adequately under thetraffic loading (particularly underthe outer wheel of heavy vehicles) and thus improve road safety. The construction method employedshould also result in reduced

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The desired outcome was to find a low cost treatment whichwould perform adequately under traffic loading

gravel usage and lowermaintenance costs.’’

The end result was the develop-ment of what is today known asthe ‘Akoseal’ — an edge-wideningprocess using a coarse-gradedemulsion-based slurry mixture.

Investigation

The edge-breaks manifested in the breaking away of the surfacing atthe edge of the carriageway andwas pronounced all along theentire route. The unpavedshoulders exhibited extensivewear, which resulted in a stepbetween the edge of the surfacingand the shoulder. From visualinspections it was determined that the shoulder gravel was more orless a G4 quality material.Although no tests were done itwas felt that the in situ materialhad sufficient bearing strength tocontinue carrying the heavyvehicle loads - probably as a result of increased compaction by trafficover the years.

Falling Weight Deflectometertests were conducted during1998, and the averageremaining life of thepavement was estimated at14.1 years. This meant, froman economic perspective, that an appropriate holding actionwas needed to postponeheavy rehabilitation for atleast 10 years.

Construction Methodology

An inspection of the damaged edges revealed that theexisting gravel surface was

still intact. Any attempt to cut andlevel the existing surface with agrader resulted in larger rocksbeing dislodged, disturbing thedensity of the in situ material.Also, placing and compacting alevelling coarse of gravel, in orderto minimise the use of gravel, ledto the formation of a biscuit layer.

It was concluded that if the gravelshoulder could be protected fromthe effects of the traffic, theapplication of a coarse-gradedslurry, placed with a continuous-mixing machine, could be a cost-effective remedial treatment forwidening the surfacing.

The shoulder was prepared asfollows prior to the application ofthe slurry:

• The shoulder was first treated with weed killer beforeremoval of the existingvegetation by hand;

• The existing shoulder wasthen swept by hand toremove any loose material.

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Figure 1: Primed shoulder

This material was reused inlater re-shouldering;

• Inverted bitumen emulsionprime was then sprayed at an application rate of 0.9 litresper square metre on theswept shoulder and left opento cure.

The use of slurry seals forresealing existing bituminoussurfaces is fairly common practicein Namibia. However conventionalslurry does have limitations in that it cannot be applied in a singlelayer with a thickness greater than 1.5 times the maximum aggregate size. For the COLTO coarse 9.5mm graded slurry, this limits theoverlay thickness to 15 mm.

In order to place a thicker layerwhich could withstand the heavytraffic loading it was necessary toutilise a continuous gradedaggregate with larger size stones.A blend of 13.2 mm and 9,5 mmsingle sized stone aggregate and-6.7 mm crusher dust was used.Anionic stablemix 60% emulsionwas added to the aggregate andcement was used as a settingagent. Sufficient waterwas added to achieve the desired workability of the mix. It was importantthat the mix hadsufficient workability toflow into the crevices ofthe existing road edge,but still stiff enough toform a sharp outsideedge after placement.

A string line was erectedon the shoulder todemarcate the outsideedge. The coarse

graded slurry was mixed in acontinuous- mixing machine andpoured into a purposely-designedbox for placing in a single pass.Initially the slurry was poured viaa chute and spread by handbetween the road edge and steelshuttering. Once confidence hadbeen built up in the performanceof the slurry mixture, a spreaderbox was used to place the slurry,eliminating the need forshuttering.

Average depth

The box was designed to bedragged from an arm behind themachine. The bulk of the box ranon the existing surface, while theoutside edge operated on aspring-loaded skid. A strike-offplate ensured that the freshlyplaced slurry would be kept levelwith the existing road surface. The average depth of the slurry was35 mm, with a maximum of 50mm at times. The fresh, widenedslurry edge was rolled with apneumatic-tyred roller three hours after placement, prior to openingto traffic.

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Picture 2: Placing coarse graded slurry

Costing and benefits

The typical daily production rateachieved for mixing and laying the slurry for the edge widening was60 m3 . This equated to a unit costrate of R14.43 per running metreor R1,374.00/m3 for mixing andplacing the slurry to a width of300mm by 35 mm deep. This costis, however, minimal whencompared to the conventionalmethod of boxing out and replac-ing with gravel and surfacing withasphalt, which would have been in excess of R45 per running metre.

This rate excludes compaction ofthe slurry, labour for traffic control and sweeping the base. The costof priming the shoulder was R1.18 per running metre. All the lattercosts would need to be included in both methods of construction.

The main benefits of widening theroad surfacing using a coarse-graded slurry placed with acontinuous-mixing machine can be summarised as follows:

• Provides a low costalternative to conventionalwidening techniques;

• Reduces the constructiontime considerably;

• Minimises the disruption totraffic during construction;

• Minimises the use ofnon-renewable materials;

• Reduces the routinemaintenance costs;

• Improves the safety byproviding a wider carriageway without a sharp drop-off.

Conclusion

“The slurry method of edgewidening has considerable time,cost and material resourceadvantages over conventionalmethods," said Mr Ako Jaf, who iscurrently the division maintenance manager for the road contractingcompany. “However this method is only appropriate to roads wheresuitable shoulder material ispresent. This was the case on Trunk Route 1 between Marientaland Rehoboth, where some 175km of edge-widening has beencompleted as part of a routinemaintenance between 1998 and2003. The decision to use coarse-graded slurry to widen the roadedge — rather than conventionalhot-mix asphalt — was found tobe the most cost effective optionat the time in light of the limitedfunds available.”

The method described has beensuccessfully used on many roadsin Namibia. The earlier sectionsare still performing well afterbeing subjected to traffic for fiveyears without any signs of failures.

Lastly the development andimplementation of this techniquecan also be seen as a goodexample of how a partnership canwork between the client andsupplier to provide a cost-effective remedial solution to overcome asevere road safety problem withinthe confines of a limited budgetfor road maintenance.

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Colas Ad: Modified Binders

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Colas’s new generationmodified binder has beensuccessfully used in a

record-breaking 1,9-millionlitre spraying operation inKwaZulu-Natal.

The contract, the largest everundertaken using an SE-2,specified the resealing of the 60km four-lane undivided N2highway between NewGuelderland and Mtunzini using amodified binder conforming to theSE-2 specification for the doubleseal on the shoulder and slowlane. The fast lanes received adouble seal constructed with anunmodified binder.

The company had to considerusing a high softening point binder given the high road temperaturesexperienced on this section of theroute in summer. A furtherconsideration was the largepercentage of heavy and lightvehicles travelling in the slowlanes. This influenced the selection of an SE-2 rather than an SE-1binder, with a minimum softeningpoint 50°C. The problems thathave been encountered withspraying an SE-1 (SBR) binder atthe required minimum softeningpoint of 57°C also supported the

decision to utilise an SBS modified binder.

Background

The high volumes of trafficencountered on the majority ofSouth Africa’s national roads, andthe concomitant increase in tyrepressures, has resulted inaccelerated deterioration ofexisting road surfaces. Researchhas shown that the engineeringproperties and performancecharacteristics required towithstand these traffic inducedforces can no longer beadequately met by conventionalpenetration grade road binders.The result was a pressing demandon the blacktop industry todevelop higher performancebinders able to deliver more costeffective and durable roadsurfacings. To answer this challenge anelastomeric binder known asCOLFLEX was developed. Thisbinder enhances the rheologicalproperties of the base bitumenthrough the addition of a specialgrade of SBS polymer andadditives. The SBS polymer usedforms a highly elastic, three-dimensional network in the

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New generation modified binder used in KwaZulu-Natal

Trevor DistinColas SA (Pty) Ltd

bitumen, dramatically increasingthe softening point and elasticrecovery properties of the basebitumen. This means that asurfacing, when subjected toheavy traffic at high roadtemperatures, will be lesssusceptible to bleeding in the case of a seal, while asphalt will bemore resistant to rutting.

Storage

In addition to its enhancedproperties, the product is storage- stable at application temperatures, unlike other commonly used SBRor rubber crumb hot modifiedbinders. It is also applied at muchlower temperatures than thelatter, which means cost savingsin heating and less time delays onsite.

Supply

The new modified binder ismanufactured under controlledconditions in purpose designedplants. Three grades are available, all complying with the new TG1guideline specifications for use insurfacing seals, hot-mix asphalt or crack sealing.The modified binder for the NorthCoast contract was supplied from

Colas’s Durban ISO 2000: 9001listed factory to the site 120 kmaway. Samples were taken dailyprior to spraying, and were testedon-site for compliance with thespecifications. The averagesoftening point recorded for theproduct was 71ºC, while thesoftening point of the80/100-penetration bitumenvaried between 44 and 48ºC.

Application

The binder was sprayed at abinder temperature of 180ºC,simultaneously across theshoulder and slow lane, with aBearcat distributor using a 6 mspray bar. The transversedistribution of the spray bar waschecked regularly using the‘bakkie’ test method to ensureuniformity. The spray rates wereadjusted according to texturedepth and ball penetration values,and 30% of the 1.1-million m² ofexisting asphalt surface was givena texture slurry pre-treatment.The spray rate for the tack coatvaried between 1.3 - 1.4 litres per m² prior to the application of the13 mm stone, while thepenetration spray rate variedbetween 1.0-1.1 litres per m²prior to the application of 6.7 mm

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Grade Application TG 1Classification

Softening PointMin ºC

S Chip & spray S-E2 57A Hot-mix Asphalt A-E2 60

C Hot pour cracksealant

C-E1 80

Table 1: Application and properties

stone. The newly constructeddouble seal was closed overnightbefore opening to traffic.

Benefits

Some of the main benefits derived from constructing the double sealusing an SBS modified binder canbe summarised as follows:

• The relative lower spraytemperature of SBS vis-à-visSBR modified binder equatesto +15oC, which renders asavings in heating costs andovertime of +1.5 hours perday;

• The high stability of the SBSmodified binder supplied onthis contract resulted in noreblending or productrejections, therebyminimising on-site delays and back hauling costs;

• The higher softening pointand improved adhesion of the SBS modified binder meantthat the newly constructedseal could be opened totraffic sooner than the80/100 used in the fast lane,without the risk to chipswhipping off at high roadsurface temperatures;

• The premium of the SBSmodified binder being R0.97per litre (R2.65 vs R1.68)amounts to an increase ofonly 6% in the cost ofconstruction - which is morethan offset by the improvedrheological properties of thebinder.

Conclusion

The use of modified binders in theapplication of surface seals onroads subjected to high volumesof traffic (with a substantialpercentage of heavy vehicles) canbe an economical means ofcarrying out periodic maintenanceto prolong the service life of asection of road before fullrehabilitation/reconstruction isrequired. The degree of bindermodification would be determinedby the design criteria i.e., traffic,climate, existing surface textureand most importantly, theconcentration of heavy vehicles on a particular section of road.

This contract demonstrated that ahighly modified SBS binder,conforming to the SE-2specification, can be sprayed witha 6-metre spray bar at a bindertemperature of 1800C without therisk of stone stripping due to poortransverse binder distribution orblocked nozzles. This makes it acost effective user-friendly binderfor surface dressings.

Although samples were taken from the distributor and tested on sitefor compliance prior to spraying,the results were always found tobe in excess of the minimumvalue. This provides the contractor and the engineer with theconfidence that the modifiedbinder can be transported andhandled on site over time withoutthe risk of the product degradingunder heating.

The product is thus ideal for use on contracts where the engineerdoes not have the luxury of an

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on-site laboratory for doing binder tests.

“While no incidents of severestone loss were recorded afteropening to traffic, the decision tokeep the section closed to trafficovernight improved aggregateretention. A slightly higheraggregate loss of 6,7mm from the

unmodified sections was evidentwhen compared with the modifiedbinder sections,” Swart said.

Colas acknowledges the input ofthe South African National RoadsAgency, the consulting engineersBCP/Stemele Bosch and contractor Haw and Inglis, in the execution of this contract.

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Distributor applying COLFLEX with 6m-spray bar and aggregatesbeing spread with a 6m-chip spreader

The Colas name has beensynonymous with bitumen binders in southern

Africa’s road constructionindustry for the past 75 years.

The roots of the company insouthern Africa date back to 1928, when a bitumen emulsion factorywas established at Bellville in theCape. Since then the firm hasundergone numerousdevelopments, includingacquisitions of constituentcompanies, changes in share-holders, and different corporateidentities. In fact the wheel hasturned a full circle: when thecompany first commencedoperations it was called ColasSouth Africa (Pty) Ltd. Later, thisname was changed to ColasSouthern Africa (Pty) Ltd, part ofthe Murray and Roberts Group.Then, in March 2000 Colas Franceacquired this company, which wasregistered under the originaltrading name — Colas South Africa (Pty) Ltd.

Evolution

The Colas name is derived fromthe wording COLd ASphalt. In the

early 1920’s an English scientistdiscovered and registered the firstpatent for bitumen emulsion. Thisevent became the foundation of anew company, which Royal DutchShell registered under the COLAStrade name. As Shell expanded itspetroleum refining and marketingactivities abroad, it also estab-lished downstream companiesunder the Colas trade mark. Themain purpose of these companieswas to further process thebitumen (produced from therefining of crude oil) into emulsion for ease of handling andapplication.

In southern Africa the companymoved from Bellville to Maitland,also establishing factories inJohannesburg, Durban, EastLondon, Port Elizabeth,Bloemfontein and Hectorspruit. In1936 operations were extendedinto Zimbabwe and later Zambia.An East Africa division was formed in 1956 with a factory in Nairobi.In 1968 an emulsion factory wasestablished in Namibia atOkahandja. The group wasstrategically well placed to supplyroad binders to the market withinsouthern and eastern Africa.

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Colas on the road for 75 years ... and still counting

T DistinColas SA (Pty) Ltd

Shareholders

During the growth and consoli-dation of the company since itsinception, there have been several major shareholders, includingRoyal Dutch Shell and Anglovaal.In keeping with Shell’s worldwidetrend of disinvestment in itsnon-core businesses, theconstituent Colas companies wereconsolidated under a singleshareholder, Murray & Roberts in1991. In very much the samevein, Shell sold its main share-holding in Colas France to the local construction giant Bouygues. Itcame as no surprise in March 2000 when Colas France decided toconsolidate its worldwide bitumenemulsion business by acquiringthe binders portion of the southern African operation from Murray &Roberts.

Constituent companies

The main constituent companiesto evolve within the group werePetrocol (1967), Much Asphalt(1965), Protea Asphalt (1976) and African Bitumen Emulsions (1930), which - in 1977 - fell under theholding company Abecol (Pty) Ltd. In 1996, the decision was made to regionalise and unify all thesecompanies under one umbrellaand one trading name, ColasSouthern Africa, which prevaileduntil restructuring took place atthe end of 1999.

With the takeover of the binderassets by Colas France, theasphalt manufacturing businesshas continued to operate underthe Much Asphalt name withinMurray & Roberts, and the

contracting arm of what used tobe part of Protea Asphalt Natalthat continues to operate withinMurray & Roberts Civils.Later developments included thetake-over of Vialit from Engen inFebruary 1997, a move thatincluded the acquisition of anumber of binder plants. Theoverall result was a comprehen-sive rationalisation andstreamlining of the bitumen binder business, which saw theintegration of the company’sIsando plant with that of the Vialitplant at Chamdor (Krugersdorp)and the integration of the Maitland operation with the Vialit plant atEpping in Cape Town.

Recent Developments

With the acquisition of the bindersbusiness from Murray & Roberts,the company has gone through aconsolidation phase. With its headoffice in Cape Town, Colas nowoperates:

• factories in Cape Town, PortElizabeth, Durban andJohannesburg;

• depots in East London,Bloemfontein andHectorspruit;

• factories outside the countryin Namibia, Zambia andKenya.

The company also has numerousmobile manufacturing plants and a wide range of applicationequipment which include:

• 3 mobile emulsion plants;• 3 mobile polymer modified

binder plants;

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• 2 mobile bitumen rubberblending units;

• 28 binder distributors;• 11 slurry and micro-surfacing

machines;• 13 mechanical horses;• More than 150 static and

mobile trailers.

In keeping with the statedintention of upgrading local plantand equipment with proveninternational technology, thecompany in South Africa hascommissioned seven new binderdistributors during the past twpyears.

Yet our greatest asset is still ourpeople — a team of 200committed individuals, recognisedas leaders in their fields. EachColas branch employs indigenouspeople who are encouraged todevelop their markets in anautonomous manner.

As a wholly owned subsidiary ofthe world’s largest bitumenemulsion supplier — with factoriesand depots strategically positioned countrywide, our commitment tothe entire South African road-construction industry is total.

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The Kruger National Parkattracts more than600 000 visitors annually,

and remains one of the majordraw cards for internationaltourists to southern Africa.

To facilitate gameviewing, thePark is serviced by a well-plannedand maintained road networkconsisting of 1800 km gravel and900 km of surfaced roads. All thesurfaced roads are sealed withsand seals, which have remainedunchanged in design from thatused when the first surfacingoperations began in 1964. Thematerials utilised in theconstruction of the sand sealconsist of natural alluvial sandsand hot penetration gradebitumen.

Bulk supply

The Kruger National Park has justcompleted the resealing of about70 kilometres of surfaced roads as part of its annual roadmaintenance program, for whichColas South Africa supplied andsprayed 650 tons of hot bitumen.However some things havechanged. In the original roadworks bitumen was supplied indrums and decanted on-site into a heating kettle before applicationby a tractor drawn sprayer. In

subsequent years the bitumen was supplied in bulk and sprayed byself-propelled pressurised distrib-utors by companies Hot Bulk andVialit.

Sand seal construction

The road pavements areconstructed to a width of 10.2m,with a surfaced width of 7.2m. For new construction the sand seal isapplied in two layers consisting ofa primary seal followed by asecondary seal. The newlyconstructed base course is firstlyprimed using MC 30 cutbackbitumen. A 150/200-penetrationgrade bitumen tack coat is applied after the prime has cured, and the river sand is spread immediatelythereafter.

Once the freshly spread river sand is rolled, the road is immediatelyopened to traffic. Back broomingof the loose sand with a dragbroom is carried out during thefirst month of the seal to ensuremaximum aggregate retention.The new surface is subjected totraffic for a period of up to sixmonths before the second sandseal is applied.

When resealing, only a single hottack coat is sprayed on theexisting aged sand seal, followed

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The seal that has stoodthe test of time

TR DistinColas SA (Pty) Ltd

by a layer of sand. The resultantcompacted thickness of the newlayer is 6 mm.

The construction and maintenance of the Park’s roads is primarilyundertaken by Park officials. Thedaily production rates achieved for sand sealing vary between 40 000and 60 000 m2. To achieve theseproduction rates, the sand isstockpiled at intervals of five kms.(The sand is excavated from theriverbed and screened through avibratory sieve with an aperture of 12 mm). The bitumen distributoris fed from a bulk road tankerpositioned at the sand stockpilearea.

Trevor Distin, Colas’s marketingmanager, stressed that “goodmeans of communication betweenthe refinery and the bulk haulier is essential to ensure continuity ofsupply at remote locations withinthe Park. As the bitumen used in

the recent reseals was suppliedfrom the Engen refinery inDurban, we had to have sixdedicated bulk road tankers onhand to meet the daily bitumendemand of the surfacing team.”

Environmental considerations

The park has seen an increase inthe annual number of vehiclesfrom three in 1929, the first timemotor vehicles visited the Park, to150 000 in 2003. While the traffic speed limit is only 50 km per houron all roads outside the camps,the maximum road surface

temperature in the northern partof the park can easily reach up to72ºC in summer months, makingit one of the warmest regions ofSouth Africa.

Despite initial resistance from the environmentalists, it wasdecided to surface the gravelroads, which were elevated abovethe adjacent terrain, for improvedviewing and drainage. The result saw a reduction in dustgenerated by vehicular traffic,which ensured that game wouldfeed on the now dust-freevegetation close to the road.According to Soekie Schoemann,manager of roads in the KrugerNational Park, a survey conductedin 1994 showed that 60% of thevisitors preferred to ride on thesurfaced roads when viewing thegame. The importation of aggregates isalso limited by the possibility of

introducing alien vegetation. Theroads are therefore constructedusing materials from local borrowpits, comprised mainly of graniticand basaltic gravel. The angularity of the coarse alluvial quartziticsand used in the seal creates anideal micro texture for a thinsurfacing. The rivers in the Parkflow from the west to the east and the granulometry depends on thedistance the sand is transported.

The Park also believes it isessential to ensure that there is no silt deposit within the sand as thiscan lead to blemishes in the

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Due to the ecological sensitivity of the region, no quarrying ofrock is allowed

surfacing. This distance travelledby the floodwater has an influence on the extent of the silt deposited.

Detailed records have been keptby the Park’s officials of all sandsealing operations since 1964.Experience has shown that thetypical expected maintenance freelife of a new sand seal is 14 years. The Park also uses a pavementmanagement system to identifyand prioritise maintenancerequirements of their surfacedroad network. The main modes ofsurface distress are edge breaksdue to erosion by stormwaterrunoff.

The use of sand seals for newconstruction and reseals hasproven very cost effective, withcurrent resealing costs in theSkukuza area running at R4.86 m² which equates to a life cycle costof R0.35/m²/year.

Renewable resource

The reduction of dust andchannelisation of water has alsoresulted in abundant vegetation on the verges adjacent to thesurfaced roads, leading toincreased animal feeding activity.Due to the low fines content of the river sand, very little dust is alsogenerated under traffic during theearly life of the seal.

The sand used in the seals iswashed down during the floodingof the rivers and redeposited in

the old river borrow pits. Thismakes it a renewable sourceunlike the gravel roads, where it is estimated that some 70,000 m³ of gravel is lost per year. The cost tothe Park of reblading andregravelling was estimated at R3.1 million in 2000.

Reduced costs

The incidence of injury to the wildanimals during the hot bitumenspraying operations is minimal, asthe animals avoid the construction site due the high levels of activity. And because the sand spreaderfollows directly behind thebitumen distributor, the exposedbinder is covered within a veryshort period. Disruption of trafficduring the surfacing operations isminimal, as the newly placedsurfacing can be opened to trafficimmediately after rolling. Unlike astone seal, the risk of windscreendamage from loose chips is alsominimised.

Other benefits include inter aliareduced road user costs and roadmaintenance costs whencompared to that of gravel roads.

The Kruger National Park’s roadmaintenance programmedemonstrates that the appropriate use and successful construction ofcost-effective durable thinbituminous surfacings using locally available materials is viable, to the benefit of the road user and thenatural environment.

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Author Index

Author Page

Airey GD . . . . . . . . . . . . . . . . . . . . . . . . . . . 125Bahia HU . . . . . . . . . . . . . . . . . . . . . . . . . . . 134Bergh A O . . . . . . . . . . . . . . . . . . . . . . . . . . . 86Beukes J . . . . . . . . . . . . . . . . . . . . . . . . . . . 151Bolk HJ. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64Botha H . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86Botha P B . . . . . . . . . . . . . . . . . . . . . . . . . . . 86Bredenhann SJ . . . . . . . . . . . . . . . . . . . . . . . . 118Cassiem I . . . . . . . . . . . . . . . . . . . . . . . . . . . 88Catin G . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151Church M . . . . . . . . . . . . . . . . . . . . . . . . . . . 158Collings D . . . . . . . . . . . . . . . . . . . . . . . . . . . 128Collop AC . . . . . . . . . . . . . . . . . . . . . . . . . . . 125Cronje P . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82De Beer M. . . . . . . . . . . . . . . . . . . . . . . . . . . 132Démarre M . . . . . . . . . . . . . . . . . . . . . . . . . . . 78Distin T . . . . . . . . . . . . . . . . . . . . 174, 180, 184, 187Emery SJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Fisher C. . . . . . . . . . . . . . . . . . . . . . . . . . . . 132Fricke I . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Greening A K . . . . . . . . . . . . . . . . . . . . . . . . . 42Hattingh J . . . . . . . . . . . . . . . . . . . . . . . . . . . 91Henderson MG. . . . . . . . . . . . . . . . . . . . . . . . . 141Hongve J . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88Horak E . . . . . . . . . . . . 34, 91, 121Houston M . . . . . . . . . . . . . . . . . . . . . . . . . . 155Hugo F . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151Hunter AE . . . . . . . . . . . . . . . . . . . . . . . . . . . 125Huurman M . . . . . . . . . . . . . . . . . . . . . . . . . . 110Jenkins KJ . . . . . . . . . . . . . . . . . 48, 110, 118, 134, 141Johansen R . . . . . . . . . . . . . . . . . . . . . . . . . . 115Jooste FJ . . . . . . . . . . . . . . . . . . . . . . . . . . . 103Kannemeyer L. . . . . . . . . . . . . . . . . . . . . . . . . 132Kasberger C . . . . . . . . . . . . . . . . . . . . . . . . . . 110Kruger S . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91Lacante S . . . . . . . . . . . . . . . . . . . . . . . . . . . 91le Bouteiller É . . . . . . . . . . . . . . . . . . . . . . . . . 78Lindsay R . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

190

Author . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page

Long F . . . . . . . . . . . . . . . . . . . . . . . . . . 147, 155Louw K. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84Luttig E . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121Mangnus S . . . . . . . . . . . . . . . . . . . . . . . . . . . 64Mataka M . . . . . . . . . . . . . . . . . . . . . . . . . . . 115Milne TI. . . . . . . . . . . . . . . . . . . . . . . . . . . . 110Molenaar AAA . . . . . . . . . . . . . . . . . . . . . . . . . 141Molenaar P . . . . . . . . . . . . . . . . . . . . . . . . . . 151Morton B . . . . . . . . . . . . . . . . . . . . . . . . . . . 121Muradzikwa S. . . . . . . . . . . . . . . . . . . . . . . . 53, 82Nordengen P A . . . . . . . . . . . . . . . . . . . . . . . . 159O’Connell J . . . . . . . . . . . . . . . . . . . . . . . . . . 53Oberholzer F . . . . . . . . . . . . . . . . . . . . . . . . . 159Onraët J . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Overby C . . . . . . . . . . . . . . . . . . . . . . . . . . . 115Paige-Green P . . . . . . . . . . . . . . . . . . . . . . . 88, 144Pinard M I . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Pretorius FJ . . . . . . . . . . . . . . . . . . . . . . . . . . 167Riley T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75Robroch S. . . . . . . . . . . . . . . . . . . . . . . . . . . 141Ross D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Sampson LR . . . . . . . . . . . . . . . . . . . . . . 21, 48, 88Semmelink CJ . . . . . . . . . . . . . . . . . . . . . . . . . 86Shunmugam R . . . . . . . . . . . . . . . . . . . . . . . . 128Standish B . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Theyse H . . . . . . . . . . . . . . . . . . . . . . . . . . . 147van de Ven MFC . . . . . . . . . . . . . . . . . . . 64, 110, 134van Wieringen JBM . . . . . . . . . . . . . . . . . . . . . . . 64Visser AT . . . . . . . . . . . . . . . . . . . . . . . . . . . 121Vos R.M. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69Voskuilen JLM . . . . . . . . . . . . . . . . . . . . . . . . . 64White L . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Wilkinson J . . . . . . . . . . . . . . . . . . . . . . . . . . 141Wise J . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167Youdale G.P. . . . . . . . . . . . . . . . . . . . . . . . . . . 69

191

192

Sabita ManualsManual 1 Construction of bitumen rubber sealsManual 2 Bituminous products for road constructionManual 5 Manufacture and construction of hot-mix asphaltManual 7 SURF+ Economic warrants for surfacing roadsManual 8 Bitumen safety handbookManual 9 Bituminous surfacings for temporary deviationsManual 10 Appropriate standards for bituminous surfacingsManual 11 Labour enhanced construction for bituminous

surfacingsManual 12 Methods and procedures - Labour enhanced

construction for bituminous surfacingsManual 13 LAMBS - The design and use of large aggregate

mixes for basesManual 14 GEMS - The design and use of granular emulsion

mixesManual 16 REACT - Economic analysis of short-term

rehabilitation actionsManual 17 The design and use of porous asphalt mixesManual 18 Appropriate standards for the use of sand asphaltManual 19 Technical guidelines for bitumen-rubber asphaltManual 20 Sealing of active cracks in road pavementsManual 21 ETB: The design and use of emulsion treated basesManual 22 Hot-mix paving in adverse weatherManual 23 Bitumen Haulier’s Code: Guidelines for Loading

Bitumen at Refineries

Asphalt Academy publications

TG1 Technical Guidelines: The use of modified binders in road construction

TG2 Interim Technical Guidelines: The design and use of foamed bitumen treated materials

Training GuidesTRIP — Technical Recommendations in PracticeHMA — Hot Mix Asphalt Training seriesHSE — Health, Safety and Environmental Guidelines for Bitumen and Coal Tar ProductsCEP — Councillor Empowerment Programme

workshop notes & CD

193

Sabita Video Training AidsVideo series on testing of Bituminous Products

Bitumen

AV-1 Penetration test / Softening point (ring and ball)AV-2 Spot test / Rolling thin film oven testAV-3 Brookfield viscosity / Ductility

Bitumen Emulsion

AV-4 Sayboldt furol viscosity / Water content of emulsionsAV-5 Sedimentation value of emulsions / Residue on sievingAV-6 Coagulation value with chippings / Coagulation value with

Portland cementAV-7 Binder content of slurry / Particle charge test

Hot-mix Asphalt

AV-8 Optimum binder content for asphaltAV-9 Marshall testAV-I0 Binder content / Moisture contentAV-11 Static creep test / Immersion indexAV-12 Rice’s density and binder absorption/Bulk relative density

and voids

Bitumen Rubber

AV-13 Ball penetration and resilience test / Dynamic viscosityAV-14 Compression recovery / Flow testAV-15 Bulk density of crumb rubber / Grading and loose fibre

test of crumb rubber

Video series on Blacktop Roads

AV-21 Black-top roads for reconstruction and developmentAV-22 Black-top surfacing and repair (with Instructor Training

Manual)AV-23 Pavement surfacing and repairs for black-top roads

Video series on Hot-mix Asphalt

AV-25 ManufactureAV-26 PavingAV-27 Compaction

For order informationcontact Sabita at:

info@sabita.co.za