A Guide to the Use of Steel Furnace Slag in Asphalt and Thin ...2 A Guide to the Use of Steel...

A Guide to the Use of SteelFurnace Slag in Asphalt andThin Bituminous Surfacings

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A Guide to the Use of SteelFurnace Slag in Asphalt andThin Bituminous Surfacings

Slag Production and Member Locations in Australasia and South East Asia

© Copyright Australasian Slag AssociationInc. All rights reserved. No part of this Guide

may be reproduced, in any form or by anyother means, without written permission from

the Publisher.

ISBN 0 9577051 31

A Guide to the Use of Steel Furnace Slag inAsphalt and Thin Bituminous Surfacings.

Published by:

Australasian Slag Association Inc.

73 Auburn Street

Wollongong NSW 2500

AUSTRALIA

Copies of this document can be obtained bycontacting the Association on +612 4225 8466

or via email: [email protected]

A Guide to the Use of Steel Furnace Slag in Asphalt and Thin Bituminous Surfacings

A Guide to the Use of Steel Furnace Slag in Asphalt and Thin Bituminous Surfacings

FOREWORD

This “Guide to the Use of Steel Furnace Slag in Asphalt and Thin Bituminous Surfacings” isthe third in a series of publications to promote understanding and the appropriate usage ofslag based products. The other publications were “A Guide to the Use of Slag in Roads”published in June 1993 and “A Guide to the Use of Iron Blast Furnace Slag in Cement andConcrete” published in April 1997.

The Australasian Slag Association is grateful for the co-operation and valuable input receivedfrom the Roads and Traffic Authority NSW, VicRoads, and the Australian Asphalt PavementAssociation in the production and the publication of this Guide.

A Guide to the Use of Steel Furnace Slag in Asphalt and Thin Bituminous Surfacings i

ii A Guide to the Use of Steel Furnace Slag in Asphalt and Thin Bituminous Surfacings

CONTENTS

1 Introduction 1

1.1 Purpose of this Guide 1

1.2 Background 1

2 Production and Processing Steel Furnace Slags 2

2.1 Furnace Processes 2

2.2 Cooling and Transporting 2

2.3 Metallics Separation 2

2.4 Processing - Crushing and Screening 3

2.5 Stockpiling - Conditioning and Weathering 3

2.6 Quality Assurance Procedures 3

3 Properties of Basic Oxygen Steelmaking and Electric ArcFurnace Slags 4

3.1 Chemistry 4

3.2 Physical Properties 4

3.2.1 Grading 4

3.2.2 Average Least Dimension 5

3.2.3 Particle Shape 5

3.2.4 Fractured faces 5

3.2.5 Density 5

3.2.6 Particle Strength 5

3.2.7 Abrasion Resistance 5

3.2.8 Water Absorption 6

3.2.9 Skid Resistance 6

3.2.10 Resistance to Stripping 8

3.2.11 Aggregate Soundness 8

3.1.12 Expansion Characteristics and CSIRO Research 8

4 Use of Steel Furnace Slags in Asphalt 9

4.1 General 9

4.2 Asphalt Mix Types 9

4.3 Advantages of Steel Furnace Slag Aggregate in Asphalt 9

5 Asphalt Mix Design using Steel Furnace Slag Aggregates 11

5.1 Overview 11

5.2 Target Grading 11

5.3 Bitumen Content 11

5.4 Resistance to Stripping 12

A Guide to the Use of Steel Furnace Slag in Asphalt and Thin Bituminous Surfacings iii

5.5 Moduli Values 12

5.6 Sample Mix Design 12

6 Use of Steel Furnace Slag in Thin Bituminous Surfacings 13

6.1 General 13

6.2 Types of Sprayed Bituminous Surfacings 13

6.3 Types of Slurry Surfacings 14

6.4 Use of Steel furnace Slag Aggregates in Thin BituminousSurfacings 14

7 Case Studies 15

7.1 BHP Steelworks Road System - Port Kembla 15

7.1.1 General 15

7.1.2 Asphalt Mix Designs 15

7.1.3 Pavement Loading and Design 16

7.1.4 Wearing Surface Performance 16

7.2 RTA Network - Illawarra District 16

7.2.1 F6 Freeway Intersection 17

7.2.2 Other Roads within the Network 18

7.2.3 Asphalt Mix Designs 18

7.3 Pennant Hills Road 18

7.4 Tomerong Bypass 20

7.5 Roberts Road, Padstow 20

7.6 Newcastle Region 20

7.6.1 Newcastle BHP Steelworks 20

7.6.2 Kooragang Island 21

7.6.3 New England Highway 21

8 References 22

9 Common Industry Acronyms & Abbreviations 24

10 Glossary of Terms 25

11 Acknowledgements 27

DISCLAIMER

The Australasian Slag Association is a non-profit organisation, which has been formed to provide aforum for exchange of information between its members and others. Since the information containedin its publications is intended for general guidance only, and in no way replaces the services ofprofessional consultants on particular projects, no legal liability or otherwise can be accepted by theAssociation for the information contained in this publication.

iv A Guide to the Use of Steel Furnace Slag in Asphalt and Thin Bituminous Surfacings

A Guide to the Use of Steel Furnace Slag in Asphalt and Thin Bituminous Surfacings 1

1.1 Purpose of the Guide.

This Guide, which is supplementary to theAssociation’s Guide to the Use of Slag in Roads,reviews in detail the use of steel furnace slag inasphalt and thin bituminous surfacings. TheGuide shows that, with technical evaluationsupported by field experience that steel furnaceslag has in many applications, propertiessuitable to replace, supplement and improveother materials. The use of steel furnace slagsin these ways also has environmental benefitsin allowing the conservation of depleting naturalresources.

The purpose of this Guide is to provideinformation to designers, specifiers andproviders of bituminous road surfacings on theproperties of steel furnace slag aggregates sothat they may be considered on an informedbasis when comparisons are being made withother aggregates.

The Guide forms part of an continuousimprovement process which aims to optimise theopportunities for the use of steel furnace slagaggregates.

As there are many types of slag, it should beemphasised that this booklet refers particularlyto basic oxygen steelmaking slag and/or electricarc furnace slag which are steel furnace slags.

1.2 Background.

Steel furnace slag is formed during themanufacture of steel. It has a complex chemicalstructure comprised of oxides and silicates.Local processors and suppliers have utilisedexpertise from overseas and Australasianexperience to develop sound managementprocedures for the handling of steel furnace slagto optimise its quality. The experience inprocessing and developments in utilisation haveresulted in a high level of performance of asphaltcontaining steel furnace slag.

Steel furnace slag has many properties, whichmake it well suited for use in bituminoussurfacings. It is a hard, dense, durable and well-shaped aggregate which has an affinity for

bitumen and acts as a strong matrix in asphalt.The skid resistance properties of steel furnaceslag make it a very useful aggregate for asphaltsurfacings including open grade asphalt, densegrade asphalt, fine gap graded asphalt and stonemastic asphalt.

In thin bituminous surfacings, the cubical shapeand skid resistant properties enhance theperformance of surfacings such as slurry seals,sprayed seals and emulsion seals.

Over the last decade the use of steel furnaceslag in asphalt has become widely accepted,particularly in the Wollongong Region of NewSouth Wales. Its acceptance in the SydneyRegion is increasing and there has been someused in the Newcastle Region of New SouthWales for Asphalt. This follows over 20 yearsexperience overseas including the US, UK andEurope where steel furnace slag has beenwidely used and is accepted as a premiumasphalt aggregate (1).

In New Zealand melter slags have beensuccessfully utilised in cold emulsion mixes andslurry seals. The coldmix has performed wellunder heavy-duty loadings and has beendeveloped with recycled rubber buffings for usein golf course walkways.

Steel furnace slags have been used in opengraded asphalt and sprayed sealing applicationson the state highway network for Transit NewZealand.

In other overseas countries blast furnace slagaggregates, which are a by-product from themaking of iron, are also used in asphalt. At thistime only steel furnace slag aggregates are usedin bituminous surfacings in Australia.

Steel furnace slag is a valuable industrial by-product. Its increased use in bituminoussurfacings will result in improved performancefor the road user and owner and a decrease inthe demand for our limited natural resources.

The locations of steel production centres withinAustralasia are shown inside the front cover.

1. INTRODUCTION

2 A Guide to the Use of Steel Furnace Slag in Asphalt and Thin Bituminous Surfacings

The slag in both EAF & BOS processes floatson the surface of the steel and is removed fromthe vessel after decanting of the molten steel.Some steel remains within the slag produced.The slag produced by both processes is similarlytreated by tipping into pits for cooling.

Tipping of Molten Steel Furnace Slag

2.2 Cooling and Transporting

Once in the pits, the material is allowed to cooluntil solidification occurs. Cooling is oftenaccelerated with the addition of controlledamounts of water. The addition of water alsoaids in cracking the slag into more manageablesizes for loaders to be able to dig and removethe slag from the pits.

The slag is loaded onto vehicles and moved toan area for further watering prior to processing.

2.3 Metallics Separation

Unprocessed steel furnace slag containsmetallics, which are separated from the slagduring processing in purpose-built metalrecovery plants. These plants operate on a basisof magnetic separation and use various typesof magnets throughout the process to removerecoverable metaltics.

The metal recovered is recycled back into thesteel making process.

After the initial removal of metallics, steel furnaceslag is then ready for aggregate production.

2.1 Furnace Processes

Steel furnace slag is formed during themanufacture of steel. It has a complex chemicalstructure of oxides and silicates.

There are two main methods of manufacturingsteel in Australasia:

• Basic Oxygen Steelmaking (BOS)

• Electric Arc Furnace Steelmaking(EAF).

In the Basic Oxygen Steelmaking process,molten iron from the blast furnace ironmakingprocess is placed in a refractory lined vessel withsteel scrap and fluxes (lime and dolomite). Largevolumes of oxygen are blown through a water-cooled injection lance into the molten materialto melt the scrap and flux and refine the metalto produce the required quality steel. After 30 to40 minutes the resultant molten products are200 to 250 tonnes of steel and 25 to 30 tonnesof slag.

Decanting Slag

In the Electric Arc Furnace Steelmaking process,iron and steel scrap and fluxes (lime anddolomite) are again placed in a refractory linedvessel. Carbon electrodes are lowered into thevessel, and an electric arc is induced. This arcis maintained to melt and refine the scrap steel,lime and dolomite. After 40 to 50 minutes theresultant molten products are 70 to 90 tonnesof steel and 8 to 10 tonnes of slag.

2. PRODUCTION AND PROCESSING STEELFURNACE SLAGS


2.4 Processing - Crushing andScreening

Steel furnace slag is processed in a mannersimilar to the production of aggregates at anyquarry.

Slag is fed to crushers and after reducing to therequired maximum size is screened into therequired grades. For asphalt and thinbituminous surfacings, aggregate sizes areusually 20 mm, 14 mm, 10 mm, 7 mm and slagfines. After conditioning and weathering, variousaggregates may be combined in designproportions to produce a blended aggregate asspecified by the customer.

It is possible to recover further metallics aftercrushing. This occurs using the same methodsas described in Section 2.3. Recovery ofmetallics after crushing is the only significantdifference when comparing operations of a slagprocessor to those of a quarry.

Steel Furnace Slag Processing Plant, PortKembla NSW.

2.5 Stockpiling - Conditioning andWeathering

Steel furnace slags in Australia may containsmall amounts of expansive product such asburnt lime and dolomite. Also, the slag particlesthemselves can be expansive until they are fullyhydrated. Sufficient moisture and time must beprovided to enable these materials to reactbefore the aggregate can be used.

This may be achieved by either:-

• Stockpiling the slag aggregates forsufficient time to allow moisture from theatmosphere (i.e. rain and humidity) to reactwith the slag particles, lime and dolomite,or

• Regularly watering the slag aggregates,thereby accelerating the conditioningprocess.

A test has been developed by the CSIRO (2) toensure sufficient weathering has taken place.This is discussed in Section 3.2.12.

2.6 Quality Assurance Procedures

In Australia, and particularly New South Wales,it is normal industry practice to supplyaggregates and roadbase under a QualityAssurance regime. Producers of BOS slagaggregates have in place registered QualityAssurance schemes.

The Quality Assurance schemes, which havebeen adapted and improved from UK and USAexperience, provide detailed procedurescovering all aspects of slag production andprocessing. Testing is performed regularly withaggregates being tested prior to dispatch toprovide the customer with confidence in slagmaterials.


3.2 Physical Properties

The physical properties of steel furnace slagaggregate are described below and summarisedin Table 3.2.

3.2.1 Grading

Steel furnace slag aggregates are screened intoindividual sizes that conform to standardaggregate grading specifications. From theindividual sizes it is possible to blend aggregatesto gradings as required for use in asphalt. Theindividual sizes are also suitable for use in thinbituminous surfacings.

The only minor difference in grading betweensteel furnace slag and quarry products is thatsteel furnace slag aggregate generally will have

a slightly lower percentage of material passingthe 75 micron sieve. This is often an advantagein asphalt as it allows more flexibility in the typeand quantity of filler added.

Graded Aggregates

3. PROPERTIES OF BASIC OXYGEN STEELMAKINGAND ELECTRIC ARC FURNACE SLAGS

3.1 Chemistry

Typical Chemistry of both BOS and EAF slags, after appropriate conditioning and weathering asdiscussed in Section 2.5, are shown in Table 3.1.

Table 3.1 - Chemistry of Steel Furnace Slags

Constituents as Oxides BOS Slag (%) EAF Slag (%)

Calcium Oxide (CaO)

% Free Lime

40

0 – 2

35

0 - 1

Silicon Oxide (SiO2) 12 14

Iron Oxide (Fe2O3) 20 29

Magnesium Oxide (MgO) 9 7.7

Manganese Oxide (MnO) 5 5.7

Aluminium Oxide (Al2O3) 3 5.5

Titanium Oxide (TiO2) 1 0.5

Potassium Oxide (K2O) 0.02 0.1

Chromium Oxide (Cr2O3) 0.1 1

Vanadium Oxide (V2O5) 1.4 0.3

Sulphur (S) 0.07 0.1


3.2.2 Average Least Dimension

The Average Least Dimension (ALD) of steelfurnace slag aggregates is generally higher thanfor naturally occurring aggregates of the samenominal size. This reflects the cubical shape ofthe aggregates.

It has also been shown that the higher ALD alsooccurs on the lower size fractions eg 4.75 mmto 6.7 mm. This property has been linked withimproved performance of asphalt in terms ofdeformation resistance. For the fraction 6.7 mmto 9.5 mm a typical ALD is 6.7 mm and for 4.75to 6.7 mm the range is 4.5 mm to 5.2 mm. Inboth cases these results exceed the value forwhat is considered to be well shaped aggregatefor use in asphalt.

3.2.3 Particle Shape

BOS slags have a predominantly cubical particleshape. This is verified by the low results forMisshapen Particles of less than 10% for 2:1and less than 2% for 3:1 when tested byproportional calipers in accordance with AS1141.14 (3).

The cubical shape of steel furnace slagaggregates is an advantage for aggregateinterlock and hence improving the deformationresistance of asphalt containing BOS Slag.

In sprayed seal applications, the particle shapeof steel furnace slag aggregates is well withinspecification limits.

3.2.4 Fractured Faces

All steel furnace slag has 100% fractured faceswhen tested in accordance with Roads andTraffic Authority (NSW) Test Method RTA T239(4). Fractured faces also improve the aggregateinterlock and hence matrix stability.

3.2.5 Density

The particle densities of steel furnace slags areas follows:-

• EAF slag

• in the order of 3,300 kg/m3, dry

• 3,400 kg/m3, Saturated Surface Dry(SSD).

• BOS slag

• 3,300 kg/m3 to 3,400 kg/m3, dry

• 3,350 kg/m3 to 3,450 kg/m3, SSD.

While these densities are higher than those ofconventional aggregates, this does not translatedirectly to a proportional increase in the cost ofplaced asphalt. While there may be increasesin haulage costs and a reduction in m3/tonne ofasphalt laid, costs of binder, mixing and placingare the same as when using conventionalaggregates.

3.2.6 Particle Strength

Steel furnace slags have high particle strength,which is an advantage for asphalt.

The high particle strength combines well withthe cubicle shape to give a matrix which is ableto transfer very high loads, and is very resistantto deformation in asphalt. Testing for particlestrength is performed in accordance with AS1141.22 (5).

The high particle strength combined with thecubical shape makes steel furnace slagaggregates suited to applications such as stonemastic asphalt and open grade wearingsurfaces. In both these types of asphalt there isconsiderable direct contact between aggregateparticles.

In sprayed seals, strong particles significantlyreduce the risk of the seal flushing due to particlebreakdown, which reduces the effective averageleast dimension of the aggregate particles.

BOS slag has a dry strength of about 250 kN.The dry strength can range up to 350 kN for thesmaller particle fractions such as 7 mm and 10mm. The wet strength is in the range of 230 kNto 300 kN.

For BOS slag the wet/dry strength variation isin the range 5 to 20% and for EAF slag the wet/dry strength variation is in the range 5 to 15%.These low values indicate materials whereparticle strength is not significantly affected bymoisture.

3.2.7 Abrasion Resistance

Abrasion resistance is tested using the LosAngeles Abrasion test in accordance with AS


1141.23 (6). The Los Angeles Value (B) for BOSslag is in the range of 12 to 18. For EAF slagthe Los Angeles Value is of the order of 16.

These results indicate that steel furnace slagshave a high abrasion resistance, which again isan advantage for asphalt. This is particularly sowhen the asphalt is in high stress areas such asheavily trafficked domestic and industriallocations and intersections.

3.2.8 Water Absorption

The water absorption of steel furnace slag issimilar to naturally occurring aggregates. Thewater absorption for both BOS and EAF slag is1% to 2% for coarse aggregates (7 mm andlarger). For fine aggregates, the waterabsorption is 2% to 4%. These results areconsistent with naturally occurring aggregatesand indicate that additional bitumen is notrequired for absorption.

The surface area of steel furnance slagaggregates is slightly greater than naturallyoccuring aggregates due to cubical particleshape and the vesicular nature of the particlesurface. Additional binder in the order of 0.5%by mass is required to coat the increased surfacearea.

3.2.9 Skid Resistance

Steel furnace slag has a Polishing AggregateFriction Value PAFV (9) (which is similar to thePolished Stone Value Test) greater than mostnaturally occurring aggregates. The range ofvalues for BOS slag is usually 52 to 58 and forEAF slag 58 to 63. The naturally occurringaggregates with PAFVs greater than thesevalues are some rhyolites and scorias whichtend to have lower wet strengths and abrasionresistance than steel furnace slag.

Steel furnace slag aggregates have beensuccessfully used in high accident areas suchas intersections and low radius curves withreduced accident rates resulting (12). Thefriction measurements determined by theSideways Force Coefficient RoutineInvestigation Machine (SCRIM) have also beenshown to be high.

Typical SCRIM results for steel furnace slagaggregates from case studies are presented inSection 7. Table 3.3 provides typicalinvestigatory skid resistance levels for SCRIMvalues. (13)

Table 3.2 - Table of Important Properties of BOS and EAF Slags

Property EAF Slag BOS Slag

Particle Density (AS1141.5 & 6)(7) (8)

3,300 kg/m3 dry3,400 kg/m3 SSD

3,300 to 3,400 kg/m3 dry3,350 to 3,450 kg/m3 SSD

Particle Shape (AS1141.14) (3) < 10% 2:1< 2% 3:1

< 10% 2:1< 2% 3:1

Dry Strength (AS1141.22) (5) 275 to 350 kN 250 to 350 kNWet Strength (AS1141.22) (5) 240 to 300 kN 230 to 300 kNWet / Dry Strength Variation(AS1141.22) (5)

5 - 15% 5 - 20%

Water Absorption(AS1141.5 & 6) (7) (8)

1% to 2% coarseaggregate

2% to 4% fineaggregate

1% to 2% coarseaggregate

2% to 4% fine aggregate

Fractured Faces (RTA T239)(4) 100% 100%LA Abrasion (AS1141.23)(6) 16(B) 12 to 18 (B)Polishing Aggregate FrictionValue (AS1141.41/42)(9) (10)

58 to 63 52 to 58

Sodium Sulphate Soundness(AS1141.24) (11)

< 4% < 4%


INVESTIGATORY LEVELS OF SFC50 at 50km/h or equivalent

0.30 0.35 0.40 0.45 0.50 0.55 0.60

CORRESPONDING RISK RATINGS

SiteCategory Site Description

1 2 3 4 5 6 7

1(See notes)

Traffic light controlledintersectionsPedestrian/school crossingsRailway level crossingsRoundabout approaches

INVESTIGATION

2 Curves with tight radius < 250mGradients > 5% and >50m longFreeway/highway on/off ramps

ADVISED

3(See notes)

Intersections

4 Manoeuvre-free areas ofundivided roads

5 Manoeuvre-free areas of dividedroads

INVESTIGATORY LEVELS OF SFC20 at 20km/h or equivalent

0.30 0.35 0.40 0.45 0.50 0.55 0.60

CORRESPONDING RISK RATING

SiteCategory Site Description

1 2 3 4 5 6 7

6 Curves with radius < 100m INVESTIGATION

7 Roundabouts ADVISED

KEY TO THRESHOLDS AT OR BELOW WHICH INVESTIGATION IS ADVISED

all primary roads, and for secondary roads with more than 2,500 vehicles per lane per day

roads with less than 2,500 vehicles per lane per day

NOTES for Table 3.2:• The difference in Sideways Force Coefficient values between wheelpaths (Differential Friction

Levels) should be less than 0.10 where the speed limit is over 60km/h; or less than 0.20 where thespeed limit is 60km/h; or less than 0.20 where the speed limit is 60 km/h or less.

• Investigatory levels are based on the minimum of the four point rolling average skid resistance foreach 100m section length.

• Investigatory Levels for Site Categories 1 and 3 are based on the minimum of the four point rollingaverage skid resistance for the section from 50m before to 20m past the feature, or for 50mapproaching a roundabout.

Table 3.3 - Examples of Investigatory Skid Resistance Levels


3.2.10 Resistance to Stripping

Steel furnace slags have a strong affinity forbitumen. This has been evidenced by excellentresults when steel furnace slag is tested by theModified Lottman procedure in accordance withRTA test method T640 (14). Samples are testedfor modulus in a dry state and then treated bysoaking in hot water and sometimes freezingprior to being tested for a wet modulus. Theresults of these tests when performed on asphaltcontaining steel surface slag aggregates haveexceeded current requirements indicating a highresistance to stripping or moisture damage.

This result would be anticipated in manyrespects due to the presence of hydrated limeon the surface of steel furnace slag particles.Hydrated lime is a known agent for improvingthe resistance to stripping and is often added toasphalt as a filler for this purpose.

For use in sprayed sealing applications, BOSslag aggregates tested in accordance with RTATest Method T230 (15)- Plate Stripping Test, willgive conforming results when the appropriateprecoating agent is used.

3.2.11 Aggregate Soundness

Testing of steel furnace slag aggregates foraggregate soundness using RTA Test MethodT266 (16) has shown that there is very littleparticle loss. Results are less than 4%compared to the current RTA specificationrequirements of less than 12%.

3.2.12 Expansion Characteristics andCSIRO Research

It is possible for small amounts of burnt lime anddolomite to be contained in steel furnace slags.Free lime contents for Australian steel furnaceslags are generally significantly lower than forother countries. For EAF slags, the amount ofburnt lime is very low, usually less than 0.5%.For BOS slags the percentage is 0 to 2%although usually less than 1%. Burnt limehydrates very quickly in the presence ofadequate moisture and steel furnace slagproducers have in place appropriate handlingprocedures to allow this hydration to occur.

To provide the asphalt producers and theircustomers with appropriate assurancesregarding the expansion characteristics of steel

furnace slags, CSIRO have developed a testmethod for characterising the potential of a steelfurnace slag sample to expand (2). The testinvolves a short immersion period of a sampleunder water after being saturated under vacuum.This allows moisture to come into contact withany expansive materials very quickly. Thegrading of the sample is taken before and aftertesting. This data is used as a measure of theextent of any breakdown of slag particles dueto the effect of expansion.

This test method is considered to be a significantimprovement on previous test procedures whichdepended on artificially elevated temperaturessuch as in an autoclave which is not reflectiveof field experience. The vacuum methodprovides an accelerated process at ambienttemperatures.

To date it has been shown that there is very littlepotential for expansion in the smaller particlesizes such as 7 mm and 10 mm, in some caseseven for slag which has had very limitedweathering. For 14 mm and larger sizes theresearch has shown that weathering is requiredin most cases before incorporation of theaggregate in asphalt. Work is continuing toobtain sufficient data to enable further guidelinesfor acceptance to be established.

It should be noted that asphalt is a veryappropriate use for steel furnace slags in respectto potential expansion. This is for a number ofreasons.

1 Bitumen coats the steel furnace slagparticles. This minimises the opportunityfor moisture infiltration into the particles.Also, the high affinity between bitumen andsteel furnace slag means that there isminimal opportunity for stripping andhence moisture infiltration into theaggregate particles.

2 Asphalt is a visco-elastic material that isable to tolerate a small amount ofexpansion.

In Australia, there have been no instances ofexpansion where appropriately weathered steelfurnace slag has been incorporated in asphalt.This is after supply of over 350,000 tonnes upto 1999.


4.1 General

This section describes the types of asphalt mixesin which steel furnace slag aggregates can beused.

4.2 Asphalt Mix Types

The types of asphalt commonly used that couldincorporate steel furnace slag aggregates are:-

• Dense Graded Asphalt (DGA)(or Asphaltic Concrete)

Dense graded asphalt comprises a mixture ofcontinuously graded aggregates, sands, fillerand bitumen which is mixed and placed hot. It isthe most common type of asphalt.

• Open Graded Asphalt (OGA)

Open graded asphalt (or porous asphalt) has alarge proportion of coarse aggregate and only asmall amount of fine aggregate resulting in ahigh void content (18 to 25%). It is used as alow noise, low spray wearing surface application

• Stone Mastic Asphalt (SMA)

Stone mastic asphalt (SMA) is a durable andrut resistant surfacing mix (sometimes alsocalled Coarse Gap Graded Asphalt (CGGA)). Ithas a large percentage of coarse aggregate withstone on stone contact, with the remaining airvoids partially filled with mastic comprising fines,filler and bitumen.

• Fine Gap Graded Asphalt (FGGA)

Fine gap graded mixes are a modified form ofdense graded mix specifically developed toachieve durable asphalt mixes for use in lighttraffic areas such as residential streets and lightlytrafficked roads .

• Ultra-Thin Asphalt (UTA) Surfacingsincluding Thin Open Graded Asphalt.

Ultra-thin asphalt surfacings have beendeveloped as a means of restoring surfacecharacteristics of otherwise sound pavementswith the shape correction and surface propertiesof asphalt but with a minimal thickness ofasphalt.

Ultra-thin asphalt surfacings are of two majortypes:

• Thin open graded asphalt placed with amodified asphalt paver that applies abinder layer immediately ahead of theasphalt layer, and

• Modified, small sized dense gradedasphalt mixes.

Detailed descriptions of these mix types andguidelines for the selection of mixes for particularapplications can be gained from AUSTROADS1998a (17).

Steel furnace slag aggregates can beincorporated into any of the above mix types asan alternative to natural aggregates or to takeadvantage of the unique properties of steelfurnace slag aggregates.

4.3 The Advantages of SteelFurnace Slag Aggregate inAsphalt.

The properties of steel furnace slag aggregatethat can be advantageously used in asphalt are:-

a) Cubical particle shape and 100 percentfractured faces provide strong aggregateinterlock and improves resistance topermanent deformation under traffic.

b) High particle strength combined withcubical particle shape and abrasionresistance makes steel furnace slagaggregate suitable for wearing surfaceapplications such as dense gradedasphalt, stone mastic asphalt and opengraded asphalt, even in heavily traffickedapplications.

c) High skid resistance makes steel furnaceslags suitable for wearing surfaceapplications in high stress situations.

d) The strong affinity for bitumen and the highresistance to stripping makes steel furnaceslag aggregates suitable for use in asphaltwhere conditions are encountered wherestripping may occur.

4. USE OF STEEL FURNACE SLAGS IN ASPHALT


e) The use of modified binders with steelfurnace slag aggregate in asphalt can beeffective in providing mixes that areresistant to bleeding and rutting in highstress situations. Guidelines for theselection and use of modified binders canbe found in AUSTROADS 1998b (18).

Case studies illustrating the use of steel furnaceslag aggregates in asphalt are provided inSection 7.

Detailed guidelines on how to incorporate steelfurnace slag aggregates into the design ofasphalt are provided in Section 5.


5.1 Overview

Mix design for asphalt containing steel furnaceslag aggregates is very similar to mix design forasphalt containing other aggregates. Someallowances however need to be made for thehigher density of steel furnace slag. Forexample, the bitumen content expressed as apercentage of the total mix, will be slightly moreon a volume basis as for asphalt containingnaturally occurring aggregates but will be slightlyless on a mass basis due to the higher particledensity of the steel furnace slag aggregate.

The AUSTROADS Pavement Research Group(APRG) in May 1997, published “Selection andDesign of Asphalt Mixes: Australian ProvisionalGuide” (19). Mix designs should be undertakenin accordance with this Guide.

5.2 Target Grading

The target grading will depend upon the end useof the asphalt. AUSTROADS Guide to theSelection of Road Pavement Surfacings (17)and local practice can be used to determine theappropriate maximum particle size or nominalsize of the asphalt. The grading will dependupon the traffic loading, underlying materials,type of bitumen to be used and the localenvironment.

To make up the required target grading, coarseaggregate, fine aggregate and filler are gradedand then a blended design is formulated. Theblending of the constituent materials may takeplace at the steel furnace slag supplier’s depotor alternatively individual particle sizes may besupplied to the asphalt producer’s plant.

5.3 Bitumen Content

The selection of bitumen content is often basedupon experience with similar mixes. It may alsobe based on achieving a minimum bitumen filmthickness. The calculation for binder filmthickness is presented below. For steel furnaceslag aggregate, its higher particle density needsto be taken into account.

Once a trial binder content has been selectedthen a trial mix may be batched at bindercontents + 0.5% of the target. Compactions atvarying numbers of cycles of the GyratoryCompactor are performed and the bulk densityand air voids are plotted against GyratoryCompactor cycles.

The following parameters are also measuredand plotted against binder content for theappropriate number of Gyratory Compactorcycles for the traffic category:

• air voids

• bulk density

• Voids in Mineral Aggregate (VMA)

• Voids Filled with Binder (VFB).

Binder Film Thickness Calculation

WhereF = film thickness (µm)Q

EB= effective binder content

(% by mass of mix)Q

BIT= total binder content

(% by mass of mix)A

c= surface area of aggregate blend

- corrected for density(m2/kg)ρ

BIT= density of binder at 25oC (t/m3)

The surface area of the aggregate is calculated from:-

TA = (2 + 0.02a + 0.04b + 0.08c +0.14d+.0.30e + 0.60f + 1.60g) x 0.20482

A = (TA x 2.65)/ ρCOMP

ρCOMP

= combined particle density of components

A = surface area of aggregate (m2/kg)a = percentage passing 4.75 mm sieveb = percentage passing 2.36 mm sievec = percentage passing 1.18 mm sieved = percentage passing 0.60 mm sievee = percentage passing 0.30 mm sievef = percentage passing 0.15 mm sieveg = percentage passing 0.075 mm sieve

5. ASPHALT MIX DESIGN USING STEELFURNACE SLAG AGGREGATES

FQ

Q AEB

BIT BIT

=−100

1 103

ρ


5.4 Resistance to Stripping

Steel furnace slags have a strong affinity forbitumen. This is due in part to the presence ofhydrated lime on the surface of weathered steelfurnace slag aggregates. Hydrated lime isadded to bitumen to promote resistance tostripping. With weathered steel furnace slag thehydrated lime is already present on the surfaceof the aggregate where it is needed.

AUSTROADS has been investigating a testingprocedure for resistance to stripping or moisturedamage for some time. At present, the ModifiedLottman procedure is the most widely used inAustralia (19).

Results from tests performed on asphaltcontaining steel furnace slag under the ModifiedLottman procedure, RTA T640 (14), shows thatsteel furnace slag aggregates have a highresistance to stripping. Results are usually over95% for the ratio of indirect modulus (wet/dry)for asphalt containing steel furnace slag as bothcoarse and fine aggregate. Currentspecifications have a minimum requirement of80%.

Field performance in regard to stripping ormoisture damage of asphalt containing steelfurnace slag has been very good.

5.5 Moduli Values

The moduli of mixes are often obtained,particularly for medium to heavily traffickedroads. The range of modulus values for full slagmixes, tested in accordance withAS2891.13.1(20), is between 3,000 and 7,000MPa. The conditions for this test represent atemperature environment of 25oC and a vehicletravel speed of about 25 km/h. The test resultsneed to be corrected to give modulus values forother temperature and design speed values.

These values are well above those usuallyassumed for design of pavement layers.

5.6 Sample Mix Design

A sample mix design is shown in the table 5.1.Other mix designs are provided in Section 7 -Case Studies

These are provided to show some of thecharacteristics of asphalt containing steelfurnace slag aggregates.

Test Met hods Results ProductionTolerances

AS 2891.2.2 (21)AS 2891.9.2 (22)

120 CyclesBulk Density (t/m3) 2.798

RTA T605 (23) Max Density (g/ml) 2.931AS2891.8 (24) Air Voids (%)

V.M.A. (%)V(f)B (%)

4.517.073.6

3.0 to 6.0MIN 15%

AS2891.2.2 (21)AS2891.9.2 (22)AS2891.8 (24)

350 CyclesBulk Density (t/m3)Air Voids (%)

2.8552.6 > 2.5%

RTA T607 (25) Bitumen Content (%) 4.9 4.8 - 5.4RTA T607 (25) Combined Aggregate Grading

37.50 mm26.50 mm19.00 mm13.20 mm9.50 mm6.70 mm4.75 mm2.36 mm1.18 mm0.600 mm0.300 mm0.150 mm0.075 mm

10010010097847862392518127

4.7

10088-9875-8965-7951-6533-4120-3012-228-16

4.0-9.03.0-6.0

RTA T607 (25) Filler to binder ratio (%) 0.9 0.6-1.2Bitumen film thickness (µm) 11.5 > 7.5Temp. of sample 162

Table 5.1 - Dense Graded 14mm Asphalt


6.1 General

This section describes the types of thinbituminous surfacings that can incorporate steelfurnace slag aggregates. The types ofsurfacings described include sprayedbituminous surfacings and those applied as aslurry.

6.2 Types of Sprayed BituminousSurfacings

The types of sprayed bituminous surfacingscommonly used that could incorporate steelfurnace slag aggregates are:-

• Primerseals

A primerseal is an initial treatment where aprimerbinder is sprayed onto a preparedpavement surface and is covered with a layerof aggregate. It allows immediate trafficking, andallows for the delay in placing the final surfacingfor logistical or operational reasons. Primersealsare generally only designed for a short life.

• Seals and reseals

A seal is formed by the spraying of one or moreapplications of binder and covering it with oneor more layers of aggregate.

• Special application seals

Strain Alleviating Membranes (SAMs)

A Strain Alleviating Membrane (SAM) is asprayed seal surfacing with a binder containinga relatively large amount of rubber or polymermodifier. It is used to absorb strains that occurin the pavement and reduce reflection cracking.

Strain Alleviating Membrane Interlayers (SAMIs)

A strain alleviating membrane interlayer (SAMI)is similar to a SAM but placed as an interlayerunder asphalt.

High Stress Seals (HSS)

A High Stress Seal (HSS) is a bituminous seal,or reseal treatment that is subject to heavier than

normal traffic loading due to braking,accelerating or turning vehicles.

Polymer Modified Binders (PMBs) are oftenutilised in SAMs, SAMIs and HSS to gainenhanced performance.

• Reinforced seals

Fibre reinforced seals

Fibre reinforced seals usually use a polymermodified emulsion and the application processuses a purpose-built sprayer which, on a singlepass:-

• Sprays binder onto the pavement,

• Cuts the required amount of fibre glass tolength, generally in the range 50mm to90mm, and blows this onto the first layerof binder,

• Sprays a second layer of binder over thecut fibres,

The bitumen and fibre layers are immediatelycovered with a lightly spread aggregate whichis locked into place using a racked in aggregate.

Geotextile Reinforced Seals

The two common types of geotextile reinforcedseal are:-

- single coat (often using a modified binder)

- double coat (using modified or unmodifiedbinder in the first spray of binder andslightly or unmodified binder in the secondlayer)

Geotextile reinforced sprayed seals areproduced by spraying a layer of bitumen onto apavement (bond coat), then covering thisbitumen with a layer of geotextile and lightlyrolling.

A single or double application seal is then appliedover the geotextile.

6. USE OF STEEL FURNACE SLAG IN THINBITUMINOUS SURFACINGS


6.3 Types of Slurry Surfacings

There are two basic types of slurry surfacings;a basic slurry mixture usually known as slurryseal and an enhanced mixture which is usuallydesignated microsurfacing.

• Slurry Seals

Slurry seals are composed of a graded mixtureof sand and fine aggregate containing filler,cement and unmodified bitumen usually in theform of an anionic emulsion and are generallyplaced in thicknesses around 1 to 1.5 times thenominal mix size. The maximum size ofmaterials in a slurry seal varies from sand to7mm aggregate (26).

• Microsurfacing

Microsurfacing is similar to slurry sealing exceptthat polymer modified bitumen emulsions areused to provide faster setting for earliertrafficking, greater resistance to rutting, greaterdurability and improved flexibility. Larger sizesof aggregate and multiple applications are alsofeasible. Other terms for microsurfacing includemicroasphalt, cold overlay and microseal.

6.4 Use of Steel Furnace SlagAggregate in Thin BituminousSurfacings

Steel furnace slag aggregates can beincorporated into any of the above thinbituminous surfacing applications as analternative to natural aggregates or to takeadvantage of the unique properties of steelfurnace slag aggregates.

The properties of steel furnace slag aggregatesthat are advantageous when utilised in thinbituminous surfacings seals are:-

a) High aggregate strength, which limitsaggregate breakdown and minimisesflushing and moisture ingress.

b) High abrasion resistance and skidresistance, which makes steel furnaceslag aggregate suitable for use in sprayedseals in high stress areas.

c) Cubical aggregate shape with a highpercentage of fractured faces whichmakes steel furnace slag aggregatesuitable for multiple application sprayedseals as it assists in the “locking up” ofthe aggregate.

In utilising steel furnace slag aggregate insprayed seal applications, the spread rate ofaggregate in m2/m3 is the same as forcomparable naturally occurring aggregates butthe higher density of the steel furnace slagaggregates needs to be accounted for inassessing the mass of aggregate required.

As with all materials the use of steel furnaceslag aggregate needs to be evaluated on a valuefor money basis.


7.1 BHP Steelworks Road System -Port Kembla

7.1.1 General

Asphalt containing steel furnace slag has beenproduced since 1980 at the Boral Asphalt Plant,which is situated within the BHP Port KemblaSteelworks. For that period asphalt containingsteel furnace slag was used in all types ofapplications within the steelworks areas andcontinues to be used throughout the works.

Since 1990, following the proven performanceof steel furnace slag asphalt’s, asphaltcontaining steel furnace slag has been used onroads for Councils, the Roads and TrafficAuthority and civil contractors (27).

The BHP internal road network consists of over20 km of roads that have been constructed from

slag materials. Some 6 km of the network wasconstructed or reconstructed during 1990/91.These roads were constructed from blastfurnace slag roadbases and surfaced withasphalt containing steel furnace slag.

7.1.2 Asphalt Mix Design

Asphalt for the steelworks road system wasdesigned using conventional methods andincorporated as much steel furnace slag aspossible. All aggregate fractions down to 7 mmwere steel furnace slag. The remainder of thegrading was made up from steel furnace slagfines and/or quarry produced fines e.g. . basaltand sand.

The bitumen used was C320 with no addedpolymers or other modifiers.

A typical mix is as shown in Table 7.1.

7. CASE STUDIES

Aggregate Grading% passing AS sieve 19.0mm% passing AS sieve 13.2 mm% passing AS sieve 9.5mm% passing AS sieve 6.7 mm% passing AS sieve 4.75 mm% passing AS sieve 2.36 mm% passing AS sieve 1.18 mm% passing AS sieve 600 µm% passing AS sieve 300 µm% passing AS sieve 150 µm% passing AS sieve 75 µm

10099917356473629189

6.7

Bitumen Content - DryAggregate Total Mix

5.5%5.2%

Voids 5.5%Voids filled by bitumen 71.1%Briquette Density 2.683 kg/m3

Maximum Density 2.838 kg/m3

Table 7.1 - Typical Asphalt Properties for a Dense Graded 14mm Mix Containing 55%Steel Furnace Slag


7.1.3 Pavement Design and Loading

Pavements within the steelworks area wereconstructed using slag roadbases. During theconstruction of pavements in 1990/91 blendedroadbase consisting of 60% steel furnace slagand 40% granulated blast furnace slag was usedfor most of the roadways. This material gainssufficient strength through reaction of lime andslag to give unconfined compressive strengthsin the range of 4 to 8 MPa. It is thus consideredto be a heavily bound material with modulusvalues over 5,000 MPa as calculated using theformulas in the AUSTROADS Guide to theStructural Design of Road Pavements (1992),Section 6.3.2.3 Modulus Correlation’s (28).Therefore these pavements have deflections ofless than 0.2 mm and very low curvatures ofless than 0.06 mm.

Most subgrade within the steelworks area iseither sand or various slags. Hence thesubgrade CBR is greater than 10 in most areas.

Asphalt placed over heavily bound material issubject to high compressive stresses due to thevery low deformation of the base layer. Thismakes rutting or other deformation of the asphaltthe most likely failure mechanism, particularly ifslow moving vehicles with heavy wheel loadingsare using the pavement. Fatigue of asphaltsurfacing on a heavily bound pavement isunlikely to occur provided that a good bond isachieved between asphalt and base. Any failureis most probably a result of fatigue in the baselayer.

The movement of large amounts of materialswithin the steelworks is facilitated by vehiclescapable of carrying heavy loads. These vehiclesimpart very high axle and wheel loads on theasphalt surfacing, as shown in Table 7.2. Theseloads are generally applied at low speeds. Allvehicles are required to travel at less than 50km/h and the larger vehicles at less than 30km/h.

Some 2,000,000 tonnes of slag are movedannually on these roads as well as variousmetallics and water carts. There are alsomovements of Cat 992 loaders whose tyres areprotected by chains. Very high local stressesoccur under the chains necessitating highdeformation and abrasion resistance from anyasphalt pavements.

There is also the movement of 1,500,000 tonnesof coal into the Port Kembla Steelworks areaand the movement of 1,000,000 tonnes ofprocessed slag products over these pavementsin triaxle semi-trailers.

Within the steelworks area there are three majorroundabouts, which are used regularly by theheavily loaded vehicles. Very high stresses areplaced on the asphalt wearing surface as highwheel and axle loads pass over these sections.

7.1.4 Wearing Surface Performance

When due consideration is given to the hightraffic loads within the road network of the Works,inspections have not revealed any areas ofsignificant deformation or rutting on asphalt.Even within roundabout areas there have notbeen any degradation due to rutting or shoving.This demonstrates the high deformationresistance of asphalt containing steel furnaceslag aggregate. Some widely spaced shrinkagecracking does appear in the pavements but thishas had no adverse effect on the performanceof the asphalt. There is also some crocodilecracking present in high stress areas indicatingthat the bound base/subbase may be nearingthe end of its design life.

7.2 Roads and Traffic Authority -Illawarra District

Roads maintained by the Roads and TrafficAuthority’s Illawarra District Office are used bymany triaxle semi-trailers transporting coal toPort Kembla for steelmaking and export. Thesame roads carry much of the industrial producefrom the Wollongong area. Most of the triaxlesemi-trailers are able to carry the maximum legalload through the use of permits and many areusing ‘super single’ tyres which have highercontact pressures and hence increaseddamaging effect.

To carry these high loadings it has beennecessary to construct heavily bound or deeplift asphalt pavements. In both cases thesepavements have asphalt wearing surfaces. Thehigh loading and low deflection pavementscreate conditions which increase thesusceptibility of asphalt to deformation throughrutting or shoving.


Picton Road, Wilton

On some sections of pavement where the largenumber of heavy vehicles were braking andturning it was decided to trial asphalt with steelfurnace slag aggregate during the early 1990’s.After initial successful trials asphalt containingsteel furnace slag became accepted for manysituations.

7.2.1 Intersection of F6 - Freeway andNorthern Distributor - Wollongong

The intersection of the F6 - Freeway and theNorthern Distributor at Gwynneville known as“Crystal Corner” has an Annual Average DailyTraffic of 50,000 vehicles with an estimatedpercentage of commercial vehicles of 20%.Previously traffic lights controlled the intersectionand southbound traffic was required to stop orslow down prior to turning right onto the NorthernDistributor. The regular stopping of the vehiclesand acceleration through the intersectionresulted in high stresses being imparted ontothe asphalt surface. This section has flat terrainprior to and through the intersection.

During the 1980’s and early 1990’s a number ofwearing surface treatments were placed on theapproaches to Crystal Corner and through theintersection. All needed to be replaced afterrelatively short periods due to deformation.

Table 7.2 - Typical Design Axle Loads used for roads within BHP - Port Kembla

Vehicle Type Gross Axle LoadingAnd Configuration

Elevated Platform Carriers

50t 96t 96t

8.9 m 2.4 m

Highway Trucks

7t 15t 22t

3.7m 2.4m 5.5 m 2.4m 2.4m

Euclids

18t 50t

4.2 m

Caterpillar 992

46t 46t

4.6 m


A 14mm dense grade asphalt containing steelfurnace slag aggregate was placed in 1992. Thebinder was C320 bitumen with 5% gilsonite.Gilsonite hardens the binder and increases rutresistance. This wearing surface performed wellup to 1998 when it was replaced during theconstruction of a grade separated intersection.In evidence of the materials suitability andperformance characteristics, steel furnaceaggregates were again selected for the newworks

7.2.2 Other Roads within the Network

Other sections of the Highway Network havealso been surfaced with asphalt containing steelfurnace slag. This has been done to increaseskid resistance in areas with high accident ratesand to increase deformation resistance. Variousbinders have been used as shown in Table IV.Early SCRIM results for these sections areencouraging. On Bulli Pass the SCRIM testinghas given mean results in the range 0.73 to 0.85after 2.5 years.

Princes Highway, Bulli Pass

This is an excellent result. It is realised thatcontinued monitoring will be required forassurance of long term performance.

Table 7.3 indicates sections of the network whichhave been surfaced with asphalt for performancereasons. Many other sections have beensurfaced with asphalt containing steel furnaceslag because steel furnace slag is the mosteconomic aggregate.

These sections are mainly 14 mm dense grademixes although Macquarie Pass includes aStone Mastic Asphalt (SMA) section withnominal size 10 mm.

Princes Highway, Helensburgh

7.2.3 Asphalt Mix Designs

The predominant mix used by the RTA is 14 mmdense grade and typical blend proportions areshown in Table 7.4. A blended 14 mm steelfurnace aggregate has been mixed with sand,filler (flyash) and bitumen, which in the typicalmix shown is of type AR 320/1000. AR 320/1000 has similar properties to C600 bitumen athigh temperatures for deformation resistanceand also has fatigue characteristics of C170bitumen at low temperatures. It is also knownas “Multigrade” bitumen. The RTA has alsomade 20 mm dense grade and 10 mm opengrade mixes containing steel furnace slag.

Mixing in accordance with the proportions shownin Table 7.4 gives a mix with typical propertiesas shown in Table 7.5. This mix has beenreported to give excellent results whencompacted using the gyratory compactor for 350cycles. The percentage of voids remaining inthe asphalt after this number of cycles has been2.5 or greater. This indicates a mix that is veryunlikely to deform.

7.3 Pennant Hills Road

A number of sections of Pennant Hills Roadbetween Carlingford and Pennant Hills inSydney are surfaced with asphalt containingsteel furnace slag. There is also one sectionthat consists of a nominal 200 mm of asphaltover lean mix concrete.

Pennant Hills Road is a very heavily traffickedroad with some of it on a steep grade. Thereare frequent intersections, which are controlledby traffic lights. During the 1990’s the road hasbeen widened, intersections improved and newpavements constructed. This initially led to a


Table 7.3 - The Binder used on Sections of the Highway Network where Asphaltcontains Steel Furnace Slag

Section BinderAngels Creek, Corrimal C320 + 5% GilsoniteKerang Ave to Rothery Road, Woonona C320 + 5% GilsoniteBulli Pass AR 320/1000 BitumenHelensburgh Curves AR 320/1000 BitumenPicton Road Climbing Lane AR 320/1000 BitumenMt Ousley to Picton Road Turning Lane AR 320/1000 BitumenF6 – Northern Distributor Intersection AR 320/1000 BitumenMacquarie Pass AR 320/1000 BitumenCambewarra Mountain and BarrengarryMountain – Kangaroo Valley

AR 320/1000 Bitumen

Product Percentage14mm blended steel furnace slag aggregate 87.9Sand 5.0Filler – flyash 2.5Bitumen - type AR 320/1000 4.6

Aggregate Grading % passing AS sieve19.0 mm% passing AS sieve 13.2 mm% passing AS sieve 9.5 mm% passing AS sieve 6.7 mm% passing AS sieve 4.75 mm% passing AS sieve 2.36 mm% passing AS sieve 1.18 mm% passing AS sieve 600 m% passing AS sieve 300 m% passing AS sieve 150 m% passing AS sieve 75 m

10097847156433023125.74.0

Bitumen Content 4.6%Voids 5.0%Voids filled by bitumen 70.3%Briquette Density 2.786 kg/m3

Maximum Density 2.932 kg/m3

Table 7.4 - Typical mix proportions for 14mm Dense Graded Asphalt Mix

Table 7.5 - Typical Asphalt Properties for a Dense Graded 14mm Mix


number of problems with deformation and ruttingof wearing surfaces.

Steel furnace slag was used by Boral Asphalt inthe wearing surface of a number of sections asa means to improve the resistance todeformation and rutting.

CSR Emoleum constructed the pavement at theintersection of the M2 Motorway on Pennant HillsRoad. This consists of three nominal 60 mmlayers of 20 mm dense grade asphalt. Steelfurnace slag was used as both the coarse andfine aggregate.

7.4 Tomerong Bypass

Steel furnace slag aggregate was chosen forthe asphalt surfacing of Tomerong Bypass,South of Nowra on the Princes Highway in NSW.In 1996 a thin (nominal 20 mm) 10 mm opengrade asphalt layer over a rubberised bitumenseal was placed on the existing pavement. Thislow cost treatment provided improved ride, skidresistance and waterproofing. Steel furnace slagwas chosen because of its shape and skidresistance properties as well as meeting all otherspecification requirements.

In an open grade mix using a strong well shapedaggregate allows for an improved matrix withgood aggregate interlock for load dispersion andtransfer.

Some 7 km of single carriageway wereresurfaced and the use of steel furnace slag inthin asphalt has become more widely accepted.

The wearing surface has performed well to date.

7.5 Roberts Road, Padstow

CSR Emoleum used steel furnace slagaggregates in the wearing surface of Roberts

Road at Padstow in Sydney. A 30 mm layer of10 mm open grade asphalt was placed and thecoarse aggregate consisted of 10 mm steelfurnace slag. Steel furnace slag was chosenfor its skid resistance properties as well as itsshape.

The paving of the wearing surface took place in1997 and after to date there is no sign of anydeterioration.

7.6 The Newcastle Region

7.6.1 Newcastle BHP Steelworks

Steel furnace slag aggregate asphalt’s havebeen used in the past throughout the Newcastlearea (29). Newcastle BHP steelworks was oneof the first sites in which slag asphalt’s weretrialed in the region.

Trials using steel furnace slag in asphalt mixeswere commenced in 1987. Due to the steelfurnace slag’s success, approximately 3 kms ofpavement have been reconstructed around theworks in areas subjected to severe traffic stress.This includes major haul roads, intersections andareas of localised braking and accelerating. Itshould be noted here that base pavements havealso been constructed using slag materials.Typical designs for 10mm and 14mm asphalticconcrete are as given in Table 7.6.

An asphalt trial in 1992 was carried out withinBHP in conjunction with the RTA (30). Thesection of road was constructed to serviceheavily laden trucks carting iron ore to stockpiles.The trial enabled the comparison of theperformance of a number of different highstrength asphalt designs. The results indicatedthat given the strength characteristics of steelfurnace slag asphalt, the slag asphalt performsas well as the high strength mixes and mixesthat had the addition of Gilsonite.

14mm Asphalt 10mm Asphalt

Size Material % in mix % in mix

14mm Steel furnace slag 21.9 -10mm Steel furnace slag 12.9 26.95/7mm Steel furnace slag 17.0 12.8Dust Crusher dust 28.4 37.1Sand Dune / river 11.8 14.4Filler Flyash 2.5 2.8

Bitumen C320 5.5 6.0

Table 7.6 - Typical Mix Designs - BHP Newcastle Steelworks


7.6.2 Kooragang Island

Trials have been carried out on KooragangIsland to test steel furnace slag asphalt’s as wellas slag base courses. The trial site was anindustrial waste disposal area and, as such, themajority of traffic was heavily laden vehicles.

The project involved the reconstruction andsealing of approximately 1km of road. Thepavement was completed in April 1992 and hasbeen subject to more than 200 truck movementsper day. An all steel furnace slag 10mm asphaltwas laid at a thickness of 35mm. The areachosen was the access way to levy banks. Themain section of pavement has shown somelongitudinal cracking associated with subpavement layer movements. High lateral forcesfrom trucks occur at a turn off area where thesteel furnace slag asphalt has performed verywell.

7.6.3 New England Highway

With the RTA involvement in the successful trialasphalt pavements on BHP land, a full trialsection was carried out on the New EnglandHighway. The trial was situated at Hexham at

the beginning of the New England Highway andis approximately 1.3km long, with a traffic countof 34,500 vehicles per day (1992) on this road.Two control pavements were also placed tocompare steel furnace slag to proven crushedrock asphalt mixes. Andesite aggregate andRhyolite aggregate were used as controlpavements.

The trial was a rehabilitation of a dividedcarriageway constructed on a low embankmenton a flat grade. The existing asphalt wasremoved and 60mm of steel furnace slag AC 20asphalt placed followed by 40mm of AC 14wearing surface incorporating the two controlsections. Mix parameters for these pavementsare shown in Table 7.7.

Class 170 binder was used with variations asrequired for the known aggregatecharacteristics.

An objective of the testing was to assess theskid resistance of the steel furnace slag mix.SCRIM testing has shown the steel furnace slagto be performing equal to that of the controlpavements in all properties, and better than thecontrol pavements from a serviceability point ofview.

Table 7.7 - Mix parameters used for the New England trialsMix Description (all dense graded)

AS Sieve Size 14mm 14mm 14mm 20mm(mm) Steel furnace slag Andesite Rhyolite Steel furnace slag26.5 10019.0 100 100 100 92-10013.2 92-100 92-100 92-100 80-949.5 73-87 73-87 71-85 65-796.7 55-69 59-73 58-72 52-66

4.75 48-62 54-68 51-65 45-592.36 40-50 46-56 43-53 37-471.18 29-39 37-47 33-43 28-38

600 µm 23-31 30-38 26-36 22-30300 µm 12-20 16-24 16-24 12-20150 µm 5.5-10.5 7.5-12.5 6.5-11.5 7-1270 µm 4.9-7.9 6.8-9.8 7.4-10.4 6.0-9.0

Bitumen Binder( % of total mix 4.9 – 5.7 5.0 – 5.8 5.1 – 5.9 4.5 – 5.3

by mass )Voids 4.7 4.7 4.7 4.7

Stability 16-40 16-40 16-40 16-40SCRIM TEST RESULTS

On curve1 0.42 – 0.58(mean 0.50

sd 0.05)

0.41 –0.67(mean 0.53

sd 0.08)On straight1 0.50 – 0.62

(mean 0.56sd 0.04)

0.45 – 0.59(mean 0.52

sd 0.05)1 After 2 to 3 years


1. MAW. K.J. (1991) Steel Slag its use andDevelopment in the United Kingdom. ASAInternational Seminar “Slag – The Materialof Choice, July 1991.

2. CSIRO (1998) BOS Slag AggregatePerformance Testing and AcceptanceCriteria - CSIRO Building Construction andMaintenance - Report BRE 050.

3. AS 1141.14-1995 Methods for samplingand testing aggregates - Particle shape,by proportional caliper

4. RTA Test Method T239 Fractured Facesof Coarse Aggregate

5. AS 1141.22-1996 Methods for samplingand testing aggregates - Wet/dry strengthvariation.

6. AS 1141.23-1995 Methods for samplingand testing aggregates - Los Angelesvalue.

7. AS 1141.5-1996 Methods for samplingand testing of aggregates - Particle densityand water absorption of fine aggregate.

8. AS 1141.6.1-1995 Methods for samplingand testing aggregates - Particle densityand water absorption of coarse aggregate- Weighing-in-water method.

9. AS 1141.41-1999 Methods for samplingand testing aggregates - Polishedaggregate friction value - Horizontal bedmachine.

10. AS 1141.42-1999 Methods for samplingand testing aggregates - Pendulum frictiontest.

11. AS 1141.24-1997 Methods for samplingand testing aggregates - Aggregatesoundness - Evaluation by exposure tosodium sulfate solution.

12. VicRoads (1993) - Steel Slag Aggregate -Materials Technology DepartmentTechnical Note 9.

13. RTA/VicRoads (1995) - A Guide for theMeasurement and Interpretation of SkidResistance using SCRIM”, August 1995.

14. RTA Test Method T640 Assessment ofPropensity for Stripping of BituminousMixes.

15. RTA Test Method T230 Resistance toStripping of Aggregates and Binders.

16. RTA Test Method T266 Soundness ofAggregates (By Use of Sodium SulphateSolution).

17. AUSTROADS (1998a) - AUSTROADSGuide to the Selection of PavementWearing Surfaces (Draft).

18. AUSTROADS (1998b) - AUSTROADSspecification framework for polymermodified binders. AUSTROADSPavement Research Group Report No.19.

8. REFERENCES


19. AUSTROADS (1997) - Selection anddesign of asphalt mixes - Australianprovisional guide. Austroads PavementResearch Group Report No.18.

20. AS 2891.13.1-1995 Methods of samplingand testing asphalt - Determination of theresilient modulus of asphalt - Indirecttensile method.

21. AS 2891.2.2-1995 Methods of samplingand testing asphalt - Sample preparation- Compaction of asphalt test specimensusing a gyratory compactor.

22. AS 2891.9.2-1993 Methods of samplingand testing asphalt - Determination of bulkdensity of compacted asphalt -Presaturation method.

23. RTA Test Method T605 Maximum Densityof Bituminous Plant Mix.

24. AS 2891.8-1993 Methods of sampling andtesting asphalt - Voids and densityrelationships for compacted asphalt mixes.

25. RTA Test Method T607 Bitumen Contentand Aggregate Grading of BituminousMixtures – Reflux Method.

26. RTA (1997) - Guide to Slurry Sealing.Pavements and Scientific ServicesBranch.

27. FENTON B (1996) - The use of steelfurnace slag aggregate in asphalt in theWollongong area. Proc 18th ARRB Conf.

28. AUSTROADS (1992) - Guide to theStructural Design of Road Pavements.

29. FRANCIS C and BROWN D - Steel SlagAsphalt - A trial in Newcastle. 9th AAPAInternational Asphalt Conference.

30. HEATON, B S (1995) - Developments inthe use of slags from iron and steel plantsin road pavements. Research report no.113.08.1995, Department of CivilEngineering & Surveying, University ofNewcastle.

31. AS 1141.11-1996 Methods for samplingand testing aggregates - Particle sizedistribution by sieving.


AC Asphaltic Concrete

ALD Average Least Dimension

ARRB Australian Road Research Board

BF Blast Furnace

BOS Basic Oxygen Steel

CGGA Coarse Gap Graded Asphalt

DGA Dense Graded Asphalt

DGB Dense Grade Base

DGS Dense Grade Sub-base

EAF Electric Arc Furnace

FGGA Fine Gap Graded Asphalt

GBFS Granulated Blast Furnace Slag

GGBFS Ground Granulate Blast Furnace Slag

GP General Purpose Cement

HSS High Stress Seal

LH Low heat Cement

OGA Open Graded Asphalt

OPC Ordinary Portland Cement

PAFV Polished Aggregate Friction Value

RTA Roads & Traffic Authority, NSW

SAM Strain Alleviating Membrane

SAMI Strain Alleviating Membrane Interlayer

SBC Slag Blended Cement

SCRIM Sideways Force Coefficient Routine Investigation Method

SMA Stone Mastic Asphalt

SR Sulphate Resisting Cement

SSD Saturated Surface Dry

SSF Steel Slag Fines

UCS Unconfined Compressive Strength

VFB Voids Filled with Binder

VMA Voids in Mineral Aggregates

9. COMMON INDUSTRY ACRONYMS &ABBREVIATIONS


Aggregates

Material complies with the specified Gradingrequirements for fine and coarse aggregates. Itmay be produced from rock, gravel metallurgicalslag or artificial stone.

Asphalt (Hot Mix)

A mixture of bituminous binder and aggregatewith or without mineral filler produced hot in amixing plant. It is delivered, spread andcompacted while hot. The term Asphalt which isin common use in Australia, is an abbreviationfor Asphaltic Concrete.

Bound Pavements

Pavements composed of granular materialsincorporating sufficient amounts of bindingagent(s) to produce significant flexural stiffness.

Coarse Aggregates

Material having a nominal size of not less than5mm and complying with the requirementsAustralian Standard AS1141.11 (31).

Cubical Aggregates Particles

An aggregates particle which is approximatelycube-shaped.

Fine Aggregates

Material having a nominal size of less than 5mmand complying with the requirements AustralianStandard AS1141.11 (31).

Grading (Aggregates)

The proportion of the various particle sizespresent in an aggregate, expressed as apercentage by mass of the whole.

Heavily Bound Base

A bound pavement layer having a UnconfinedCompressive Strength (UCS) value greater than4 MPa.

Mat

A surface condition in which the aggregate isproud of the surface and the binder isapproximately two thirds of the way up the sidesof the aggregate particles.

Polished Aggregate Friction Value

A measure, on scale of 0 to 100, of the resistanceof an aggregate to polishing under the action oftraffic as determined in standard laboratory tests.

Polishing

A condition whereby the surface of an aggregatebecomes smooth under the action of traffic. Thistends to reduce tyre/road friction.

Precoating

The coating of an aggregate with an oil, waterof bituminous based material, with or without anadhesion agent, to suppress the dust andimprove the subsequent adhesion of bituminousmaterial.

SAM (Stain Alleviating Membrane)

A sprayed seal with the binder containing arelatively large concentration of rubber orpolymer modifier. It is used to provide amembrane to absorb strains that occur in a roadpavement and thereby reduce reflectioncracking.

SAMI (Stain Alleviating MembraneInterlayer)

Similar to SAM, but provided as an interlayerbefore placing an Asphalt overlay (usually athicker and more highly modified binder than aSAM)

Skid Resistance

The frictional resistance provided by thepavement surface to the vehicle tyres duringbraking of cornering manoeuvers. It is usuallymeasured on wet surfaces.

10. GLOSSARY OF TERMS


Sprayed Seal

A thin surface layer of bituminous materialcovered with aggregate which, as the uppermostpavement layer, is directly subjected to theforces of vehicular traffic.

Vesicular Slag

The term vesicular as applied to slag means theparticles contain voids which tend to beunconnected to each other, occurring throughouteach particle and appearing as blind holes onthe particle surface.

Weathered Steel Furnace Slag

Steel furnace slag is considered to be weatheredwhen it has been exposed in its finished form toboth atmospheric and controlled conditions toallow the full hydration of any lime present .

Wearing Surface

That part of pavement upon which the traffictravels.

Bleeding (seals)

A surface condition in which an excess of freebinder completely covers the aggregate. Thereis no surface texture.

Flushed Surface

A smooth pavement surface due to the presenceof excess binder.

Gyratory Compactor

A controlled method of compacting asphaltsamples where an axial load is applied 1 to 3degrees from the perpendicular as the samplerotates. Each application of the load is termeda cycle.

Modulus (resilient)

The ratio of stress to recoverable strain underrepeated loading conditions. Also referred toas elastic stiffness.

Rutting

The longitudinal vertical deformation of apavement surface in a wheel path, measuredrelative to a straightedge placed at right anglesto the traffic flow and across the wheel path.

Shoving

Lateral displacement of pavement structure bybraking, accelerating or turning vehicles.

Stripping

A separation of the binder film from the surfaceof aggregate, usually in the presence of water.


This Guide is the product of a considerable co-operative effort between the NSW Roads and TrafficAuthority, VicRoads, Transit New Zealand, the Australian Asphalt Pavement Association and theAustralasian Slag Association to better understand the behaviour of and develop the utilisation ofindustrial slag products.

The valuable contribution of experience and expertise of the following people is gratefullyacknowledged:-

Val Brizga Roads & Traffic Authority NSW

Warren Carter CSR Emoleum

Norm Clifford Steelstone

Russell Crabb Boral Asphalt

Gordon Dobson Steel Cement

Bruce Fenton Australian Steel Mill Services

Chris Francis Roads & Traffic Authority NSW

Phil Gallagher Australian Asphalt Pavement Association

Peter Hanley Steelstone

Brian Heaton Consultant

Craig Heidrich Australasian Slag Association

Wayne James Australian Steel Mill Services

David Jones BHP Port Kembla

Adam Kelly Steelstone

Joe Krsul Roads & Traffic Authority NSW

Lance Midgley VicRoads

David Mangan Australian Asphalt Pavement Association

Greg McAlister Australian Steel Mill Services

Ian Moreland Slag Reduction New Zealand

Doug Prosser Australasian Slag Association

Martin Venour BHP Newcastle

Phil Walter Roads & Traffic Authority NSW

Geoff Youdale Consulting Engineer

Special thanks go to Bruce Fenton and Geoff Youdale who co-ordinated the compilation and editingof the Guide.

11. ACKNOWLEDGEMENTS

A Guide to the Use of Steel Furnace Slag in Asphalt and Thin ...2 A Guide to the Use of Steel...

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