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http://wmr.sagepub.com/content/21/2/83The online version of this article can be found at:

DOI: 10.1177/0734242X0302100202

2003 21: 83Waste Manag ResMustafa Tuncan, Ahmet Tuncan and Altan Cetin

The use of waste materials in asphalt concrete mixtures

Published by:

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International Solid Waste Association

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Waste Manage Res 2003: 21: 8392

Printed in UK all rights reserved

Waste Management & Research 83

Copyright ISWA 2003

Waste Management & ResearchISSN 0734242X

IntroductionDisposal of industrial wastes is a worldwide problem.

Environmental awareness of the drawbacks of landfill sites

is forcing nations to look for better ways to recycle indus-

trial wastes. The use of industrial wastes as additives in

asphalt mixtures is not a new technique. Additives have

been used in road construction for more than 80 years (Al-

Abdul-Wahhab & Al-Amri 1991). They are incorporated

in asphalt mixtures to enhance the properties and perfor-

mance of asphalt concrete pavements. Large scale use of

rubber from waste tyres in asphalt mixtures appears attrac-

tive and promising from the engineering and environmen-

tal point of view. Pavements made of rubber and plastic

modified asphalt concrete have better skid resistance, lesscracking and a longer pavement life in comparison to con-

ventional asphalt pavements (Al-Abdul-Wahhab & Al-

Amri 1991, Flynn 1993). Studies have been done to

investigate the effects of rubber particles from tyres in the

preparation of asphalt concrete mixtures in the laboratory.

In these investigations, scrap rubber was used to modify

the asphalt at 10%, 20% and 30% of aggregate weight

(Haas et al. 1983). Khedaywi et al. (1994) reported that

while the softening point of the binder increased, penetra-

tion and ductility of the binder decreased with increasing

rubber content.

Mustafa TuncanAhmet TuncanAltan CetinDepartment of Civil Engineering, Anadolu University, Iki Eylul

Kampusu, 26470, Eskisehir, Turkey.

Keywords: Waste tyre, crumb rubber, waste plastic, Marshall sta-bility, indirect tensile strength, moisture susceptibility, wmr 5064.

Corresponding author: Mustafa Tuncan, Department of CivilEngineering, Anadolu University, Iki Eylul Kampusu, 26470,

Eskisehir, Turkey.

Fax: 90-222-323 95 01 E-mail: [email protected]

Received 23 January 2003, accepted in revised form 18 February

2003.

The purpose of this study was to investigate (a) the effects

of rubber and plastic concentrations and rubber particle

sizes on properties of asphalt cement, (b) on properties of

asphalt concrete specimens and (c) the effects of fly ash,

marble powder, rubber powder and petroleum contami-

nated soil as filler materials instead of stone powder in the

asphalt concrete specimens. One type of limestone aggre-

gate and one penetration-graded asphalt cement (75-100)were used. Three concentrations of rubber and plastic (i.e.

5%, 10% and 20% of the total weight of asphalt cement),

three rubber particle sizes (i.e. No. 4 [4.75mm] 20 [0.85

mm], No. 20 [0.85mm] 200 [0.075mm] and No. 4

[4.75mm] 200 [0.075mm]) and one plastic particle size

(i.e. No. 4 [4.75mm] 10 [2.00mm]) were also used. It

was found that while the addition of plastic significantly

increased the strength of specimens, the addition of rub-

ber decreased it. No. 4 [4.75mm] 200 [0.075mm] rub-

ber particles showed the best results with respect to the

indirect tensile test. The Marshall stability and indirect

tensile strength properties of plastic modified specimens

increased. Marble powder and fly ash could be used as

filler materials instead of stone powder in the asphalt con-

crete pavement specimens.


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Mustafa Tuncan, Ahmet Tuncan, Altan Cetin

84 Waste Management & Research

Many studies have shown that the addition of rubber to

asphalt concrete mixtures in amounts ranging from 10% to

30% of the asphalt binder increases the viscosity and resis-

tance to moisture damage and reduces the susceptibility to

temperature and the tendency to flow (Haas et al. 1983,

Lalwani et al. 1982, Oliver 1982). Addition of crumb rub-

ber to hot-mix asphalt concrete was reported by severalauthors to improve rheological properties of the asphalt

such as viscosity, softening point, penetration, temperature

susceptibility, strength and durability (Khedaywi et al.

1994).

Deterioration of asphalt pavements leading to perma-

nent deformation or rutting is one of the major problems in

Turkey. It has considerably reduced the service lives of

pavements and increased maintenance costs. In hot

weather, the dynamic stiffness of the asphalt pavement

decreases and thus higher stresses are transmitted to the

layers below, resulting in greater deformation (Brown1978).

Using industrial wastes in the asphalt concrete pave-

ment can not only decrease environmental problems but

also improves some properties of the pavement. Several

authors investigated the effects of fly ash on properties of

asphalt mixtures (Ali et al. 1996). Results of these studies

indicated that fly ash could be used as a mineral filler to

improve the resilient modulus characteristics and stripping

resistance. The New Jersey Environmental Engineering

Protection department conducted a study to evaluate the

feasibility of using petroleum contaminated soil in the pro-

duction of hot-mix asphalt (Meegoda et al. 1996). Test

results showed that this asphalt produced a much better

paving material with higher stability values than standard

hot-mix asphalt. The durability of the asphalt against freez-

ing and thawing was the same as that of the control mix-

tures.

In this study, the effects of waste materials as additives

and filler materials on the properties of asphalt concrete

pavement mixtures were investigated.

Materials

Aggregate

One type of limestone aggregate was used in this study.

This aggregate is the most commonly used for asphalt con-

crete pavement construction in Turkey. The gradation and

some other properties of the aggregate determined in the

laboratory are given in Fig. 1 and Table 1 respectively.

Asphalt cement

One penetration-grade asphalt cement 75-100 is widely

used in Turkey. This asphalt was obtained from the Asphalt

Work Site of the Municipality of Eskisehir, Turkey. This

type of asphalt was chosen because it is widely used in

pavement construction in the city of Eskisehir. Table 2

gives a summary of the test results obtained from the

asphalt cement in the laboratory. Amounts of saturates,

aromatics, resins and asphaltenes in the asphalt cement are5.1%, 63.8%, 18.6% and 12.5%, respectively.

Crumb rubber

Crumb rubber used in this study was obtained by chopping

scrap automobile and truck tyres. The specific gravity of

the rubber is 1.11. Crumb rubber from three size ranges,

No. 4-20, No. 20-200 and No. 4-200 was used as a modifi-

er at 5%, 10% and 20% by total weight of asphalt cement.

Grain size distributions of crumb rubber are given in Fig. 2.

The scanning electron microscopy picture of a crumb rub-

ber particle between the No. 40 and No. 60 sieves is shownin Fig. 3a.

Plastic

Discarded plastic grocery bags, dry cleaning bags and

household plastics were used. The use of polymers to mod-

ify the characteristics of the asphalt pavement in asphalt

cement mixtures is acceptable in the highway construction

industry (Flynn 1993). Some of the concerns about the use

of recycled plastic as an asphalt cement modifier are per-

formance and durability, cost effectiveness, availability,

recyclability, health and environmental impacts. The plas-

tic generally comes from grocery bags and household plas-

tics. In this study, plastic from a single size range between

the No. 4 and No. 10 sieves was used as a modifier at 5%,

10% and 20% by total weight of asphalt cement. The scan-

ning electron microscopy picture of a plastic particle is

shown in Fig. 3b.

Filler materials

Industrial wastes such as fly ash, marble powder and petro-

leum contaminated soil (PCS) were used as filler materialsto prepare asphalt concrete mixtures. Some properties and

hydrometer analyses of fly ash, marble powder and PCS are

given in Table 3 and Fig. 4 respectively.

Fly ash

Fly ash is an industrial residue of the coal burning process.

It was obtained from a coal fired power plant near the city

of Ankara, Turkey. This fly ash is a fine silt size material

consisting of spherical glassy particles and is composed of

45.68% silicon oxide, 9.04% aluminum oxide, 7.04% iron

oxide and 15.20% calcium oxide. The total amount of sili-

con, aluminum and iron oxides is 61.76%. The minimum

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85Waste Management & Research

acceptable requirement is 50% to be a type C fly ash(Conner 1990). Type C fly ash, used in this study, has a

higher lime content than type F fly ash and therefore it can

be self-cementing.

Petroleum contaminated soil (PCS)

Petroleum drilling waste was used as petroleum contami-

nated soil. Wastes contain drilling mud and cuttings.

Drilling mud is normally classified as oil-based or water-

based (Rogers 1963). Drilling cuttings are the solid cut-

tings which are brought to the surface from a well during

boring. PCS consists of chloride, barite, bentonite clay,

caustic soda, carboxyl methyl cellulose and crude oil.

Laboratory studyExperiments were conducted at the laboratories of the

Department of Civil Engineering at Anadolu University in

Eskisehir, Turkey. In this study, the optimum asphalt

cement content in the regular asphalt concrete without

any waste was found to be 4.5%, using the Marshall stabil-

ity test. Therefore, an asphalt cement content of 4.5% by

weight of aggregate was used for all specimens regardless of

the amount of rubber or plastic added to the asphalt

cement. The Marshall stability test procedure was used to

prepare test specimens. A total of 160 rubber and plastic

modified specimens were prepared. Five specimens of each

industrial waste modified mixtures were tested. A total of

220 industrial waste modified specimens were prepared.

The Marshall stability and flow test (ASTM D1559), theindirect tensile test (AASHTO T283) and the compres-

sive strength test (ASTM D1074) were performed to

determine the mechanical properties of industrial waste

modified asphalt concrete specimens. The moisture sus-

ceptibility test (AASHTO T283) was also performed by

using both the Marshall stability and the indirect tensile

tests for conditioned and control specimens. Softening

point, penetration and ductility of rubber and plastic mod-

ified asphalt cement were determined using ASTM D36,

ASTM D5 and ASTM D113, respectively.

Table 1: Properties of Aggregate.

Properties Values

Los Angeles Abrasion Test [%] 24(ASTM C131)

Soundness [% loss of Na2SO4 ] 1.0(ASTM C88)Flakiness Index [%] 11(BS 812)Stripping Resistance [%](ASTM D1664)

AC (60-70)* 55-60AC (150-200)# 50-55

*AC (60-70): Asphalt cement penetration of 60-70#AC (150-200): Asphalt cement penetration of 150-200

Fig. 1: Grain Size Distributions of Aggregate and Upper and Lower Limit Specifications of Turkish General Directorate for Highways 1994.



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Preparation of rubber and plastic modified asphaltcement mixtures

First, asphalt cement was heated in an oven at a tempera-

ture of at least 160C. Second, the required amount of

asphalt was weighed into the beaker, then the amount of

rubber and plastic required to yield the desired rubber-to-

asphalt ratio or plastic-to-asphalt ratio was added. The

beaker was placed on a hot plate to maintain a mixing tem-

perature of at least 160C. Third, the laboratory mixer was

placed so that the propeller was about 15 mm above the

bottom of the beaker. The mixer was then started, and the

prepared amount of rubber or plastic was added gradually

to the beaker while stirring. The speed of the mixer was

increased up to 500 rpm. The mixing was continued for at

least 30 minutes until a homogeneous rubber or plastic

modified binder was obtained. Finally, the rubber or the

plastic modified asphalt cement was mixed with the heat-

ed aggregate to prepare rubber or plastic modified asphalt

concrete mixtures.

Preparation of industrial waste modified asphalt concretemixtures

Five percent of stone powder was replaced by an equal

weight of industrial waste finer than the No. 200 sieve.

These wastes were oven dried at 105C before using as

fillers. Specimens were prepared according to the Marshalltest procedure (ASTM D1559).



Table 2: Properties of Asphalt Cement.

Properties Values

Penetration [0.1 mm] at 25C, 100 g, 5 s 83(ASTM D5)Softening Point [0C], ring and ball 45(ASTM D36)Ductility [10 mm] at 25C 100+

(ASTM D113)Specific Gravity 1.024(ASTM D70)

Table 3: Properties of Filler Materials.

Type of Filler Specific pH Electrical Conductivity Organic Matter Gravity [mS/cm] Content [%]

(ASTM D854) (EPA Method 9045) (Wilcox 1946) (ASTM D2974)

Fly ash 2.33 12.34 10.38 1.1

Petroleum Contaminated Soil 2.66 8.74 35.8 6.51Marble Powder 2.72 9.69 0.24 1.5

Fig. 2: Grain Size Distributions of Crumb Rubber.



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Experimental results

The effect of rubber and plastic concentration and rubberparticle size on properties of asphalt cement

Fig. 5a shows that the softening points of the asphalt

cement increases with an increase in the amount of rubber

and plastic added. In the case of plastic, there is a chemi-

cal reaction between the asphalt and plastic. Therefore,

plastic modified asphalt cement has a very high softening

point. Addition of rubber and plastic reduces susceptibilityto temperature of asphalt cement according to softening

points. Fig. 5b shows that the penetration decreases with

an increase in the amount of rubber and plastic in the

asphalt cement. Asphalt cement with No. 4-20 rubber par-

ticle sizes shows higher penetration, whereas asphalt

cement with No. 4-200 and No. 20-200 rubber particle

sizes shows the lowest penetration. Addition of rubber gen-

erally improves the viscosity of asphalt cement. Fig. 5c

shows that the ductility of asphalt cement decreases with



Fig. 3: Scanning Electron Microscopy Pictures of : (a) Crumb RubberSample (between No. 40 and No. 60); (b) Plastic Sample.

Table 4: Marshal Stability Test Results of Control Specimens.

Properties Values

Asphalt Content [%] 4.5Bulk Specific Gravity 2.470

Void Total Mix [%] 2.33Flow [mm] 2.44Stability [kN] 15.53

Fig. 4: Hydrometer Analyses of Industrial Wastes.



7/11

increasing rubber and plastic content. Asphalt cement

with finer than No. 100 rubber particle size shows slightly

higher ductility, whereas asphalt cement with No. 4-20

rubber particle sizes shows the lowest ductility. Asphalt

cement with finer than No. 100 and No. 20-200 rubber

particle sizes are more homogeneous than that of No. 4-

200 and No. 4-20 rubber particle sizes. Addition of coarse

rubber particles reduces the penetration and ductility of

asphalt cement. Addition of plastic in the asphalt cement

also decreases the penetration and ductility to around zero

and makes the asphalt cement very hard, stiff and brittle.

The effect of rubber and plastic on asphalt concretemixtures

Marshall stability and flow test

The Marshall stability test results of control specimens pre-

pared with an optimum asphalt cement content of 4.5%

are given in Table 4. The variation of Marshall stability andflow values are given in Fig. 6. It was found that while the

addition of rubber decreased the Marshall stability, the

addition of plastic increased it. This is because plastic melts

in the asphalt cement and therefore binds the aggregates.

Marshall stability of rubber modified asphalt concrete spec-

imens are above the limit value of 8.83 kN (Standard

1994), except with the addition of 20% rubber between

No. 4 and No. 20 sieves. Marshall stability significantly

decreased after adding 10% rubber. Addition of rubber

increased the flow properties of asphalt concrete mixtures.

However, the addition of plastic decreased it. When theMarshall stability and flow test standard is applied, the flow

values of modified mixtures are within the limits of 2 mm

and 4 mm (Standard 1994). While the flow values of

crumb rubber particle sizes between No. 20 and No. 200

sieves and between No. 4 and No. 200 sieves were within

the limits, those of No.4-20 rubber particle sizes were

above the limits. Therefore, this mixture was not suitable

for the asphalt concrete pavement. The addition of rubber

above 10% did not show good results according to the

Marshall stability test (Al-Abdul Wahhab & Al-Amri

1991).

Indirect tensile strength test

The indirect tensile strength test is very useful in predict-

ing long-term flexible pavement performance (Foxworthy

et al. 1996). The variations of indirect tensile strength with

rubber and plastic content are given in Fig. 7. Indirect ten-

sile strength of mixtures decreased as the amount of rubber

increased. Addition of 20% rubber between No. 4 and No.

200 sieves decreased indirect tensile strength values by 7%.

However, the largest decrease (36%) occurred by mixingrubber particle sizes between No. 20 and No. 200 sieves.

This was because of the fine rubber particles in the mix-

ture. When the rubber consisted of coarse rubber particles,

indirect tensile strength increased. This occurred when the

rubber particle sizes were used between No. 4 and No. 200

sieves. Tensile strength of plastic modified asphalt cement

was increased, with an increase in the amount of plastic.

Asphalt cement with 20% plastic increased the indirect

tensile strength value by 69%. A chemical reaction

occurred between the plastic and asphalt cement and also

between the crumb rubber and asphalt cement, therefore,

the strength of specimens increased.



Fig. 5: Effect of Rubber or Plastic Content on : (a) Softening Point;(b) Penetration; (c) Ductility of Asphalt Cement.



8/11

Compressive strength test

The compressive strength test results are given in Fig. 8.

While additions of 5% and 10% rubber increased the

strength values by 10% and 5% respectively, compared to

the control specimens, addition of 20% rubber decreased

its value by 12%. Addition of rubber increased the strain

capacity of specimens. Therefore, addition of rubber

increased the flexibility and toughness. These results

showed that the addition of rubber improved the strengthof the pavement, as long as the amount added in the trial

did not exceed about 12%.

Moisture susceptibility test

Damage to asphalt concrete pavements caused by moisture

is an important problem. The moisture damage in asphalt

concrete is due to the loss of adhesion or the loss of cohe-

sion, but both mechanisms are interrelated (Hicks 1991).

It can be seen from Fig. 9a that Marshall stability of rubber

and plastic modified and conditioned specimens were

slightly increased and decreased, respectively, compared to

the control specimens. Indirect tensile strength of rubber

and plastic modified and conditioned specimens were

slightly decreased compared to the control specimens (see

Fig. 9b). Moisture susceptibility of the plastic modified and

conditioned specimens was stronger than that of the rub-

ber modified and conditioned specimens. While indirect

tensile strength of rubber modified and conditioned speci-

mens decreased compared to the control specimens, the

Marshall stability of rubber modified and conditioned spec-

imens increased. In fact, the Marshall stability of rubbermodified and conditioned specimens should decrease com-

pared to the control specimens. Therefore, Marshall stabil-

ity did not show a good indication of the strength

variations of rubber modified asphalt concrete mixtures.

However, the indirect tensile strength test showed more

reliable results than the Marshall stability test.

The effect of industrial wastes as filler material on asphaltconcrete mixtures

Stone powder was replaced by fly ash, marble powder, rub-

ber powder and petroleum contaminated soil (PCS) as a

filler material. These wastes were sieved to pass the No.



Fig. 6: (a) Marshall Stability; (b) Flow Values of Rubber or PlasticModified Specimens.

Fig. 7: Indirect Tensile Strength of Rubber or Plastic ModifiedSpecimens.

Fig. 8: Compressive Strength of Rubber Modified Specimens.



9/11

200 sieve. The Marshall stability and flow test, the indirect

strength test, the compressive strength test and the mois-

ture susceptibility test were performed on these industrial

waste modified asphalt concrete mixtures.

Marshall stability and flow test

Marshall stability and flow test results are given in Fig. 10.

While addition of rubber significantly reduced the

Marshall stability value by 73%, addition of marble powder

increased its value by 10% compared to the control speci-

mens. Addition of PCS and fly ash decreased the Marshallstability values by 1% and 6%, respectively. When the

Marshall stability and flow test standard is applied, the flow

values of mixtures were within the limits of 2 mm and

4 mm (Standard 1994), except for rubber powder modi-

fied specimens. The addition of marble powder showed the

best results according to the Marshall stability test.

Indirect tensile strength test

The indirect tensile test results are given in Fig. 11. While

addition of fly ash increased the indirect tensile strength

value by 1.9%, additions of marble powder and PCS

decreased its values by 0.7% and 25%, respectively, com-

pared to the control specimens. It can be concluded that

PCS negatively affects the asphalt concrete pavement.

This is because it consists of bentonite clay and organic

matter. The addition of fly ash showed the best result

according to this test.

Compressive strength test

It can be seen from Fig. 12 that addition of marble powder

and PCS decreased the compressive strength values by

11% and 27% respectively. However, there was no change

with the addition of fly ash. There was a similarity betweenthe results of the unconfined compressive test and the

indirect tensile test. Addition of fly ash showed the best

result for this test.

Moisture susceptibility test

While the addition of fly ash increased the Marshall stabil-

ity of conditioned specimens compared to control speci-

mens, the addition of other wastes decreased it (Fig. 13a).

The addition of wastes decreased the indirect tensile

strength of conditioned specimens (Fig. 13b). The addition

of fly ash showed the best results according to the Marshall

stability test. However, none of the wastes showed a good



Fig. 9: (a) Marshall Stability; (b) Indirect Tensile Strength of Rubber orPlastic Modified Conditioned Test Specimens and Control Specimens.

Fig. 10: (a) Marshall Stability; (b) Flow Values of Industrial WasteModified Specimens.



10/11

result according to the indirect tensile test.

Conclusions

Addition of crumb rubber

(1)Addition of rubber increased the softening point anddecreased the penetration and ductility of asphalt

cement. Addition of coarse rubber particles disturbed

the homogeneity and also reduced penetration, soften-

ing point and ductility of asphalt cement. Viscosity and

susceptibility to temperature of asphalt cement were

also improved.

(2)Addition of rubber decreased the Marshall stability but

increased the flow properties. All Marshall stability and

flow values of rubber modified asphalt concrete speci-

mens were within the limits of 8.3 kN and 2-4 mm

(Standard 1994), respectively, except for addition of20% rubber particle sizes used between No. 4 and No.

20 sieves according to the Marshall stability and flow

test method. Marshall stability were reduced when the

amount of rubber was more than 10%.

(3)Addition of 10% rubber particle sizes between No. 4

and No. 20 sieves in modified specimens showed the

best results according to the indirect tensile strength

test. Indirect tensile strength values of 5% and 10% rub-

ber modified mixtures were the same as those of the

control specimens.

(4)Addition of rubber increased strain capacity. Therefore,

flexibility and toughness were improved. Compressive

strength were reduced when the amount of rubber was

more than 12%.

(5)While the Marshall stability of conditioned specimens

were slightly increased, indirect tensile strength of con-

ditioned specimens decreased by 25% compared to the

control specimens. Therefore, indirect tensile test

apparently showed more reliable results than the

Marshall stability test. Marshall stability test does not

show the decrease in the stability of conditioned speci-mens.

Addition of plastic

(1)Addition of plastic significantly increased the softening

point and decreased the penetration and ductility of

asphalt cement. Therefore, susceptibility to temperature

and viscosity of asphalt cement were significantly

increased.

(2)While the addition of plastic to asphalt cement signifi-

cantly increased Marshall stability and indirect tensile

strength, it decreased the flow properties. This is

because plastic melts when it is mixed with asphalt



Fig. 11: Indirect Tensile Strength of Industrial Waste ModifiedSpecimens.

Fig. 12: Compressive Strength of Industrial Waste Modified Specimens.

Fig. 13: (a) Marshall Stability; (b) Indirect Tensile Strength of IndustrialWaste Modified Conditioned Test Specimens and Control Specimens.



11/11



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TO), Washington, D.C.

Al-Abdul-Wahhab, H. & Al-Amri, G. (1991) Laboratory evaluation of

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cement, therefore, stronger mixtures are obtained. This

is due to the chemical reaction between the plastic and

the asphalt cement. It also makes the asphalt cement

very hard, stiff and brittle.

(3)Addition of plastic significantly increased the indirect

tensile strength of specimens.

Using industrial wastes as filler material

Additions of fly ash and marble powder showed the best

results among the industrial wastes used in this study.

However, addition of rubber powder showed the worst

result among them because of its very low specific gravity

compared to the others. Fly ash and marble powder can be

safely used instead of stone powder as a filler material in

the asphalt concrete pavement. While the addition of

petroleum contaminated soil (PCS) significantly decreased

the indirect tensile and compressive strength, it did not

decrease Marshall stability. This is because PCS containsbentonite clay and organic matter. It can be concluded

that the indirect tensile test showed more reliable results

than the Marshall stability test.

References


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