Laboratory Assessment of Highways

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Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 4(2):194-200 (ISSN: 2141-7016)

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Laboratory Assessment of Highways Asphalt Bitumen inSouthwest of Nigeria

I. Akiije and V. A. Moyinwin

Department of Civil and Environmental Engineering,

University of Lagos, Lagos, Nigeria

Corresponding Author: I. Akiije

___________________________________________________________________________AbstractThis paper reports laboratory tests conducted while evaluating some properties of bitumen used in the

production of hot mixed-hot laid asphalt of three different asphalt plants in southwest of Nigeria. The bitumen

properties investigated included determination of the purity or contamination of the bitumen sample.Determination of the temperature at which bitumen sample used will attain standard fluidity for the purpose of

mixing with aggregate. The bitumen properties also investigated included determination of the sample grade atthe temperature of 25C and 60C. These properties were investigated through Solubility, Softening Point,

Penetration and Saybolt Viscosity tests respectively. Although all the three asphalt plants samples passed the

Softening Point and the Solubility tests but could not satisfy the specification values set up as standards for

Penetration and Saybolt Viscosity tests. Southwest of Nigeria is in the tropical region and the standardspecification values for Penetration test should be AC 60/70 but the results obtained are of about AC 85/100that is meant for temperate climate regions. It is pertinent to note that the harder the grade of bitumen, the

lower the penetration value and the better its use for the production of quality asphalt in tropical region. Thesignificance of this study is that results of experiments on bitumen samples from the three selected asphalt

plants in southwest of Nigeria are unsatisfactory when related to the expected standard approved grades of

both Penetration and Saybolt Viscosity tests. Unsatisfactory results from Penetration and Saybolt Viscosity

tests as shown in this study could significantly affect the performance of asphalt leading to the premature

failure of flexible pavements as presently prominent in southwest of Nigeria.__________________________________________________________________________________________

Keywords:solubility, softening, penetration, viscosity, flexible, pavement

INTRODUCTIONBitumen in this study is referring to asphalt cement,

a binder in the production hot mixed-hot laidasphalt of flexible pavement. A mixture of bitumenfrom fractional distillation during the refining

petroleum crude and non-volatile oil such as

propane, butane or pentane by heating can produce

graded bitumen of usable consistency for flexiblepavement Wright (2003). Bitumen is usually graded

in accordance with its viscosity or penetration at aspecified temperature, Kadyali and Lal (2008),

Garber and Hoel (2010). Bitumen is useful in the

production of asphalt primarily because of theirexcellent binding or cementing power and their

waterproofing properties, as well as their relativelylow cost, Adedimila (2000). Asphalt is a relatively

thin high quality bituminous surface material on topof series of granular layers of a flexible pavement,Akiije and Oyekan (2012).

A flexible pavement is a structure that maintains

intimate contact with and distributes loads to the

subgrade and depends on the interlock, particle

friction, and cohesion for highway stability.Highway is a system which its functions allow for

traffic movement in six recognizable stages of

main, transition, distribution, collection, access andtermination AASHTO (2008).

Hot mixed-hot laid asphalt is usually produced byproperly blending bitumen, coarse aggregate, fine

aggregate, and filler (dust) at temperatures ranging

from about 80C to 165C. The surface of flexible

pavement varies depending on the type of bitumenused and climatic conditions. Flexible pavement

distresses do occur where unsatisfactory bitumenproperties manifested in the asphalt used for a

highway. Distress is defined as an indication of

unfavourable pavement performance or signs ofimpending failure, or any unsatisfactory

performance of pavement sort of failure Oguara(2006). Too much bitumen in asphalt can cause

distortion. Pavement distortion is any change of thepavement surface from the original shape inform ofrutting, corrugation, shoving and depressions. A rut

is a longitudinal surface depression which maydevelop in the wheel paths. Corrugation is a form of

plastic movement typified by ripples across the

bituminous pavement surface that occurs usually at

points where traffic starts and stops. Corrugationsare usually caused by lack of stability of asphalt

layers in warm weather or lack of aeration of

Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 4(2): 194-200

Scholarlink Research Institute Journals, 2013 (ISSN: 2141-7016)jeteas.scholarlinkresearch.org


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asphalt mixture. Shoving is a lateral displacementof paving material due to action of traffic generally

resulting in the bulging of the surface caused bylack of stability in bituminous layers.

Another sort of distress that can be caused byunsatisfactory bitumen is pavement disintegration.

Disintegration of asphalt is the breaking up of apavement into small, loose fragments that dislodged

aggregate particles and if not stopped in its early

stages can progress until the pavement requirescomplete rebuilding. Two common types of

disintegration are potholes and ravelling. Potholesare bowl-shaped holes of various sizes in the

pavement surface resulting from localizeddisintegration by weakness in the asphalt resulting

from too little bitumen among other causes.Ravelling is the progressive disintegration ofaggregate particles in a pavement from the surface

downward or edges inward. Ravelling is caused bytoo little bitumen in the mix, or overheating of the

bituminous mix. Skid hazard due to slippery on

pavement surfaces can be the result of a film of

bitumen bleeding from the asphalt surface.

The aim of this paper therefore is to carry out

laboratory tests on bitumen samples used in theproduction of hot mixed-hot laid asphalt for

highway pavement from three different asphaltplants in southwest of Nigeria. The objective is to

evaluate some properties while determining both

consistency and quality of the bitumen samplesobtained by evaluating their conformity with the

relevant established standard specifications.Specifically, to carry out the following laboratory

tests on the samples obtained that includes

Solubility Test, Softening Point Test, PenetrationTest and Saybolt Viscosity Test. The scope of work

in this study is on the determination of the bitumengrade at temperature of 25C and 60C. Another

work is the determination of the temperature atwhich bitumen attained its standard fluidity for the

purpose of mixing with aggregate.

Also, work done is on the determination of the

purity of bitumen and contamination in bitumen.

The purpose of this study is to identify statistically

the satisfactory performance of the asphaltproduced for the construction of highway

pavements from three asphalt plants within the

southwest of Nigeria for safety considerations. Thesignificance of this study is that majority of asphalt

bitumen being used in the southwest of Nigeria

which is in tropical region are of materials meant

for temperate climate and this is a fatal reason for

premature failure of their flexible pavements.Premature failure of roads makes highways

dangerous and leading to high rate of fatal accidentsof vehicles which is a trend to loss of lives and

properties.

MATERIALSBitumen used for road construction are viscous

liquid or semi-solid materials that is black to brownin colour with less free carbon and consisting

essentially of hydrocarbons and their derivatives,

which are soluble in trichloroethylene Brennan andOFlaherty (2002). According to Wright (2003)

bitumen produced from petroleum is softer but asthe bitumen cools down to room temperature, it

becomes a semisolid viscous material. The

consistency of the residues produced duringpetroleum refinery can be further modified to

paving bitumen by the solvent deasphalting, or thesolvent extraction processes. Bitumen produced

from the vacuum-steam distillation exists as asemisolid at room temperature, and usually proper

workability can be attained by heating it to atemperature of 120C to 165C to liquefy it for

purpose of mixing it with heated aggregates. Table

1 is showing the typical uses of bitumen that arecategorized into Viscosity gradedoriginal,

Viscosity gradedresidue and Penetration graded

which is useful in the selection of any particular

type of pavement construction. The consistency of

bitumen materials is important in flexible pavementconstruction because it is a tool to indicate the

grade or class of the available bitumen at aspecified or a particular temperature. It is important

that the temperature at which the consistency isdetermined be specified as in Tables 2 and 3, since

temperature significantly affects consistency of

asphalt materials. Tables 2 and 3 are showing thepenetration and viscosity grades of bitumen or

asphalt cement that are normally available in themarket for the production of asphalt for flexible

road pavements respectively.

Table 1: Typical Uses Of Bitumen

Source: Wright, 2003


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Table 2: Penetration Grades of Bitumen


Table 3: Viscosity Grades Of Bitumen


METHODOLOGYThe particular grade of bitumen or asphalt cement

is designated by its penetration and viscosity, bothof which will give an indication of the consistencyof the material at a given temperature. In this study

bitumen examined were samples from threeselected asphalt plants that produce asphalt for

pavement construction in Lagos, Ogun, Oyo, Osun,Ondo and Ekiti States within the southwest of

Nigeria. Representative samples of bitumen were

collected from three selected asphalt plants for fourdifferent months. Laboratory tests were carried on

bitumen samples obtained from the three selectedasphalt plants at the department of Civil and

Environmental Engineering, University of Lagos.Solubility Test was carried out for it was used tomeasure the amount of impurities in the bitumen

material. Softening Point Test, Penetration Test andSaybolt Viscosity Test were also carried out in the

course of this study. Three tests were carried out on

each of the monthly collected representative sampleof bitumen per asphalt plant. The mean value of the

three tests was considered as the sample

representation for the monthly Solubility, Softening

Point, Penetration and Saybolt Viscosity Tests pereach asphalt plant.

Solubility Test2 g of bitumen sample from the plant was dissolved

in 100 ml of trichloroethylene a solvent for 30minutes and the solution was filtered through a

filter paper into a crucible. The material thatretained on the filter paper was then dried and

weighed and used to calculate the percentage of the

weight of the original bitumen sample. Thesolubility test of bitumen sample with full detail of

the equipment used is fully described in theAASHTO D T44-03 (2006).

Softening Point TestThe bitumen sample obtained from the plant was

heated to a temperature between 75C and 100C asa consideration for approximate softening point to

be in complete fluid form. Heated bitumen was then

poured into standardized two rings of 16 mm insidediameter and 6.5 mm high attached to a metal plate

and left for 30 minutes to cool at room temperature.After which a steel ball of 10 mm was placed on

each of the bitumen of the standardized two rings.

The assembled instrument of the rings, bitumen andsteel balls was placed inside a beaker with distilled

water. The boiling water was then stirredcontinuously while noticing the temperature change

using an emerged thermometer. As the temperatureincreases gradually the bitumen softened and

thereby permitting the ball to eventually sink to thebottom plate etched 25 mm below the rings. Thetemperature at which the balls touched the bottom

plate were observed and recorded of the meanvalue. Details of Softening Point Test on bitumen

sample with full detail of the equipment used are

fully described in the ASTM D36-95 (2000).

Penetration TestThe bitumen sample was softening to a pouring

consistency temperature between 75C and 100Cand stirred to make it homogenous and free from air

bubbles and water. The sample was then pouredinto a standard container to a depth of 15 mm more

than the expected penetration depth. The bitumen

sample container was then placed in a temperaturecontrolled water bath at a temperature of 25C for

one hour and after then it was removed and laterplaced at the penetrometer equipment for the

penetration test. Here, the penetrometer needle was

brought in contact with the surface of bitumensample and the reading of dial was set at zero. After

which the standard needle with a load of 100 g wasallowed to penetrate the bitumen sample for exactly

5 seconds. The penetration is given as the distancein units of 0.1 mm as the needle penetrates the

bitumen sample. AASHTO D T49 (2006) gives full

details of the penetration test.

Saybolt Viscosity Test

The Saybolt Furol Viscometer with tube 10.8 cm

long and 4 cm in diameter. An orifice of 0.3 cmdiameters is connected to an opening of 1 cm

diameter at the bottom of the tube. The standard

tube was then placed in a larger water bath of theinstrument fitted with an electric heater and astirring device. A heated bitumen sample that has

been filtered through a 100m mesh was placed

directly into the viscometer tube closed with a

stopper at the 1 cm diameter opening until the levelwas above the flow rim. The bitumen sample was

then heated to 60C temperature. Immediately uponreaching the 60C temperature, the stopper was

removed, and the time in seconds for exactly 60 ml


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of the asphalt material to flow through the orificewas recorded. Description in full details of the

equipment for the Saybolt Viscosity Test is inAASHTO T72-97 (2001).

RESULTS AND DISCUSSIONThe summary of the bitumen representation sample

results on the solubility test obtained from the threeselected asphalt plants in the southwest of Nigeria

is in Table 4. Table 4 is showing how the results of

the solubility test are in conformity to AASHTO DT 44-03 (2006) and the FMW (2007). It is also

obvious in Table 4 that the bitumen samplerepresentation from each of the three asphalt plants

passed the solubility test at a level of higher free ofimpurities contamination. Assurance could also be

noted that the material tested for asphalt productionis not tar for in tars case the presence of impuritieswill be higher and will not conform to the standard

specification although they both have black tobrown colour. Moreover, it must be noted that the

solubility value of bitumen sample tested is not

lower than that of the standard specification values.

This is because such a situation will lower the hot

mixed-hot laid asphalt bonds and finally causeuntimely deterioration of the pavement under the

traffic.

In the case of softening point tests, summary of thebitumen representation sample results obtained

from the three selected asphalt plants in the

southwest of Nigeria is in Table 5. The results ofTable 5 on softening point tests are in conformity to

ASTM D36-95 (2000) and FMW (2007). Theconformance of the tested samples to standard

specifications is an indication that the bitumen

materials when used for hot mixed-hot laid asphaltwill be of higher workability, proper enhanced

mixing with aggregates and the possibility of fireoutbreak is eliminated.

Table 6 contains the summary of the penetrationtest result values on bitumen representation samples

obtained from the three selected asphalt plants inthe southwest of Nigeria. The table is showing how

the results of the penetration test are validated using

AASHTO D T 49-06 (2006) and FMW (2007)

standard specification values. A glance at thesample results of penetration tests of Table 6 and

comparing it to standard penetration grades

specification of bitumen of Table 2 it is obviousthat one third of the results conformed to AC 60/70while two thirds conformed to AC 85/100. It is to

be noted that AC 60/70 is a harder bitumen material

while AC 85/100 is a softer one. However, it could

be argued that the majority of the bitumen materialsin used for asphalt production in southwest of

Nigeria which is in tropical region are suitable fortemperate climate region countries. It is the

addition of solvent such as propane, butane and

pentane used on soft vacuum-steam-refinedbitumen from petroleum refinery that brings about

harder asphalt bitumen materials. The additionaluse of solvents during further distillations to

produce harder bitumen warrants more cost and

manufacturers may want to elude this process oreconomise that will not satisfactorily produce

bitumen of AC 60/70. Marketers will buy thematerials they found on ground or go for cheaper

bitumen and for this reason unsuitable bitumen may

be imported into Nigeria at the expense of usingsame to produce unsatisfactory asphalt in

Southwest of Nigeria.

Table 7 contains the summary of the viscosity testresult values on bitumen representation samples

obtained from the three selected asphalt plants inthe southwest of Nigeria. The table is showing howthe results of the viscosity test are validated using

AASHTO T 72-97 (2001) and FMW (2007)standard specification values. Comparing the

sample results of viscosity tests of Table 7 to

standard viscosity grades specification of bitumen

of Table 3 it is obvious that the whole results is not

conforming to grade AC 20. Bitumen of AC 20 isthe recommended grade as found in Table 1 for the

production of hot mixed-hot laid asphalt forhighways, airports and parking areas in tropical

regions of which southwest of Nigeria is a part.Bitumen at the viscosity grade of AC 20 will

provide a uniform film for binding action in tropical

regions whereas bitumen with higher viscosity willresists compacting effort and bitumen with lower

viscosity will only lubricates the aggregate particles(Gupta and Gupta, 2007).

Table 4: Bitumen Sample Solubility Tests


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Table 5: Bitumen Sample Softening Tests

Table 6: Bitumen Sample Penetration Tests

Table 7: Bitumen Sample Viscosity Tests

Figure 1: Viscosity Bitumen Sample at Location A

Figure 2: Viscosity Bitumen Sample at Location B

Figure 3: Viscosity Bitumen Sample at Location C

It is apparent in Table 3 that the bitumen samples

tested are of AC 2.5, AC 5 and AC 10 whilerelating results obtained and that the bitumen arenot useful for hot mixed-hot laid asphalt in

southwest of Nigeria being a tropical region. Thebitumen samples tested revealed that the materials

could be useful for the production of hot mixed-hot


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laid asphalt in temperate regions or used forbitumen-aggregate applications of surface

treatments in tropical regions as shown in Table 1.Figures 1 through 3 are charts presented in order to

vividly illustrate and compare viscosity bitumen

sample results from the three selected asphalt plantsin the southwest of Nigeria. It is obvious from the

three charts that none of the bitumen from theasphalt plants of comply with standard

specifications of AASHTO T 72-97 (2001) and

FMW (2007).

CONCLUSIONThe main conclusions derived from the bitumen

samples obtained from the three selected asphaltplants in the southwest of Nigeria after the

laboratory tests are as follows:1. The three selected asphalt plants representative

bitumen samples passed the laboratory

solubility tests with the experimental resultscope within 99.90% - 99.99% when compared

to standard specifications of 99.00% - 99.99%

of AASHTO T 44-03 (2006) and FMW

(2007).

2. The three selected asphalt plants representativebitumen samples also passed the laboratory

softening tests because ASTM D36-95 (2000)and FMW (2007) specification for same is

within the range of 40% - 55% while theexperimental result scope is 44C- 55C.

3. Considering the penetration tests carried out in

the laboratory on the three selected asphaltplants representative bitumen samples,

validating results obtained with 60/70penetration values at 25C temperature of

AASHTO T 49-06 (2006) and FMW (2007)

specification show that:i. Asphalt plant A bitumen sample

passed the test once of the four testscarried out therefore having a score of

25% compliance.ii. Asphalt plant B bitumen sample also

passed the test once of the four tests

carried out therefore having a score of25% compliance.

iii. Asphalt plant C bitumen sample

passed the test twice of the four tests

carried out therefore having a score of50% compliance.

4. The three asphalt plants representative bitumen

samples failed the Saybolt Viscosity laboratorytests at 60C temperature because AASHTO T72-97 (2001) and FMW (2007) specification

for same is within the range of 1600 - 2400

poise while the experimental results scope are

as following :i. Asphalt plant A bitumen sample

Saybolt Viscosity laboratory tests at60C temperature results are within

the range of 170.24 - 940 poise.

ii. Asphalt plant B bitumen sampleSaybolt Viscosity laboratory tests at

60C temperature results are withinthe range of 171.20 - 988 poise.

iii. Asphalt plant bitumen sample Saybolt

Viscosity laboratory tests at 60Ctemperature results are within the

range of 598.00 - 1033.60 poise.5. The unsatisfactory results from Penetration and

Saybolt Viscosity tests as shown in this study

could significantly affect the performance ofasphalt leading to the premature failure of

flexible pavements as presently prominent insouthwest of Nigeria.

RECOMMENDATIONThe general practice in Nigeria is in using imported

bitumen of which the majority is from temperatecountries where they use different bitumen grade

that is not conforming to asphalt being produced inNigeria. In view of this it recommended that

1. The Federal Government of Nigeria should

endeavour to establish at least a factory for

now in each of the six geopolitical zones of the

nation to be importing bitumen for the purposeof upgrading same to the required 60/70

penetration and 1600 - 2400 poise of viscositygrade.

2. The suggestion by the Asphalt Institute (1965)that 85/100 penetration could be used for

paving highways and streets in Hot climate for

medium to light traffic should be discouragedin Nigeria. This is because asphalt produced by

manufacturers using bitumen of 85/100penetration meant for medium to light traffic

could end up been used for heavy traffic

highways and streets that can lead to prematurefailure of the pavements.

REFERENCESAASHTO T 44-03, (2006): Solubility ofBituminous Materials, in Standard Specificationsfor Transportation Materials and Methods of

Sampling and Testing, Twenty-Sixth edition,American Association of State Highway and

Transportation Officials, Washington, D.C

AASHTO T 49-06 (2006): Penetration ofBituminous Materials, in Standard Specifications

for Transportation Materials and Methods of

Sampling and Testing, Twenty-Sixth Edition,American Association of State Highway andTransportation Officials, Washington, D.C

AASHTO T 72-97 (2001): Saybolt Viscosity,

Standard Specifications for TransportationMaterials and Methods of Sampling and Testing,

Twenty-Sixth edition, American Association ofState Highway and Transportation Officials,

Washington, D.C


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AASHTO, (2008): A Policy on Geometric Designof Highways and Streets, American

Association of State Highway and TransportationOfficials, Washington, D.C

Adedimila, A. S. (2000): Bitumen: Nigerias OtherBlack Gold? Inaugural Lecture Series, University

of Lagos

Akiije, I. and Oyekan, G. L (2012): Stabilization

Assessment of Aggregates in Asphalt ConcreteMixtures, International Journal of Scientific &

Engineering Research, Volume 3, Issue 4, pp 695-699

ASTM D 36-95 (2000): Standard Test Method for

Softening Point of Bitumen (Ring-and-BallApparatus), American Society for Testing andMaterials, Philadelphia, PA

Brennan, M. J. and OFlaherty C. A. (2002):

Materials Used in Road Pavements, Chapter 5 in

Highways the Location, Design, Construction &

Maintenance of Pavements, edited by OFlaherty,

C. A., 4th Edition, Butterworth-Heinemann

FMW (2007): Pavement and Materials Design inHighway Manual Part 1: Design, Volume 3,

Federal Ministry of Works, Abuja, Nigeria

Garber, N. J., and Hoel, L. A. (2010): Traffic and

Highway Engineering, 4th edition, Cengagelearning, Stamford, USA

Gupta, B. L. and Gupta, A. (2007): Roads,

Railways Bridges Tunnels & Harbour Dock

Engineering, Standard Publishers Distributors,1705-B, Nai Sarak, Delhi

Kadyali, L. R. and Lal, N. B. (2008): Principles

and Practices of Highway Engineering (IncludingExpressways and Airport Engineering), KhannaPublishers, Delhi

Oguara, T. M. (2006): Highway Engineering

Pavement Design Construction and Maintenance,

Malthouse Press Limited, Lagos

The Asphalt Institute, (1965): The Asphalt

Handbook, the Asphalt Institute, College Park,

Maryland, USA

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Laboratory Assessment of Highways

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