re

mtiorot HNMatioand

facindoneovatiotent oninousfractuepeated, high asphalt

that are developed by using different laboratory testing modes.The most common methods for characterizing the fatigue behaviorof asphalt mixtures are the Wohler approach, dissipated energymethod and fracture mechanics approach [4]. Various kinds of as-phalt mixes with different properties show different fatigue behav-

iors. Specic properties such as aggregate gradation, air void andasphalt content have direct effects on asphalt mixtures [13].

ated and compared with hot mix asphalt HMAmixtures and the ef-fects of different mix properties on fatigue life were assessed.

2. Objective

The main objective of the research presented in this paper wasto characterize the fatigue behavior of SMA and HMA mixtures interms of gradation type, coarseness and neness of gradation, tem-perature and asphalt content. An experimental study of fatigue lifein asphalt concrete material has been made. Fatigue life of each

* Corresponding author. Tel.: +98 21 64543005; fax: +98 21 6414213.E-mail addresses: f.moghadas@aut.ac.ir (F.M. Nejad), eaaki@aut.ac.ir (E. Aaki),

Construction and Building Materials 24 (2010) 11581165

Contents lists availab

Construction and B

evgishar@gmail.com (M.A. Mohammadi).rut rst [1]. Previous researches have been reported that thereare several factors affecting the fatigue lives of bituminous mix-tures. According to the NCHRP APPENDIX II-I and SHRP-A-404[2,3], pavements with different mix stiffness, thickness, subgrademodulus, air void and asphalt content exhibit different fatiguebehaviors.

Numerous models of varying sophistication have been devel-oped to predict the fatigue behavior of asphalt concrete includingelastic, viscoelastic, elastoplastic, viscoplastic, and crack models

reective cracking and reduced noise pollution, however drainageof binder and higher primary costs could be mentioned of its disad-vantages [15]. Due to both the gap-graded nature of SMA mixesand the relatively large proportion of asphalt content, it needs sta-bilization in order to inhibit draindown of asphalt and this require-ment is commonly achieved by adding bers or polymer modiersto the mix [16,17].

In this research, fatigue behavior of SMA mixtures with threedifferent gradations by NMAS of 19, 12.5 and 9.5 mm were evalu-1. Introduction

Asphalt pavements in general arelems world-wide. So much has beenof the mix through research and innlem of fatigue cracking is still persis

The fatigue resistance of a bitumwithstand repeated bending withoutself in the form of cracking from rbeen shown that low asphalt contentto show fatigue cracking, and high a0950-0618/$ - see front matter 2009 Elsevier Ltd. Adoi:10.1016/j.conbuildmat.2009.12.025g serious distress prob-to improve the qualityns. However, the prob-asphalt roads.

mixture is its ability tore. Fatigue manifests it-trafc loading. It has

ir void mixes are pronecontent mixes tend to

Stone matrix asphalt SMA is a gap-graded hot mix that hasgained popularity world-wide. SMA was rst devised in Germanyin the 1960s. In the United States, the SMA technology started anevolution in the early 1990s and has been widely used since [57]. Most of the reports by the researchers highlighted the mixturesgreat potential in resisting permanent deformation or rutting, butignored any potential fatigue resistance of the SMA [8].

Some of the properties of SMA mixtures include its high rutresistance [911], high durability [1214], improved resistance toFatigue behavior of SMA and HMA mixtu

F. Moghadas Nejad, E. Aaki *, M.A. MohammadiDepartment of Civil Engineering, Amirkabir University of Technology, Tehran, Iran

a r t i c l e i n f o

Article history:Received 1 June 2009Received in revised form 5 November 2009Accepted 18 December 2009Available online 12 January 2010

Keywords:HMASMAFatigueIndirect tensile testStiffness modulus

a b s t r a c t

Fatigue crack is a main forvehicular loading, deterioration and growth of the micried out on hot mix asphalmaximum aggregate sizesand fatigue prediction equgradation type, coarseness

journal homepage: www.elsll rights reserved.s

of structural damage in exible pavements. Under the action of repeatedn of the asphalt concrete materials in pavements caused by the accumula-and macro cracks gradually takes place. The indirect tensile tests was car-MA and stone matrix asphalt SMA mixtures comprising different nominalAS in three temperatures of 5, 25 and 40 C. Stiffness modulus, fatigue livesn of the mixtures were developed and characterized in terms of aggregateneness of gradation, temperature and asphalt content.

2009 Elsevier Ltd. All rights reserved.

le at ScienceDirect

uilding Materials

ier .com/locate /conbui ldmat

mixture was measured and the fatigue life prediction equation wasobtained using the regression analysis. Fatigue behavior of the twomixtures was compared to each other and the effect of each mix-ture parameter was investigated.

3. Research approach

To satisfy the objectives of this study, HMA and SMA specimenswere prepared at optimum asphalt content. Limestone aggregate,asphalt with 60/70 penetration, and two aggregate gradationswere used in preparing HMA specimens and the same materialswhere used in preparing SMA specimens with three aggregate gra-dations. Fatigue tests were performed on the prepared Marshallspecimens with a diameter of 10 cm and height of 7 cm to evaluatethe effect of aggregate gradation type, temperature, asphalt con-tent, neness and coarseness of gradation on fatigue life and to ob-

respectively. The limestone was used in the mixture for both

including the mixtures properties are presented in Table 3. The

3.3. Methodology

Fig. 2. Aggregate gradation curve of SMA mixtures types C, B, and A by the NMAS of9.5, 12.5 and 19 mm, respectively.

Table 1Properties of coarse and ne aggregates.

Properties Value

Coarse aggregatesLos angeles abrasion value (%) 25Water absorption (%) 1.2Particle density (g/cm3) 2.622

Fine aggregatesWater absorption (%) 1.8Particle density (g/cm3) 2.597

Table 2Physical properties measured of bitumen.

Parameter measured Test method (AASHTO) Value

Specic gravity at 25 C (g/cm3) T228 1.014Penetration at 25 C (0.1 mm) T49 60Softening point (R and B C) T53 52Viscosity at 120 C (centistokes) T201 882Viscosity at 135 C (centistokes) T201 407Viscosity at 160 C (centistokes) T201 135Ductility at 25 C (cm) T51 >10

Table 3Summary of design results.

Parameter HMAtype H1

HMAtype H2

SMAtype A

SMAtype B

SMAtype C

NMAS (mm) 9.5 12.5 19 12.5 9.5Asphalt content (%) 5.07 4.95 7.8 5.5 6.5Stability 849 800Bulk specic

gravity (g/cm3)2.511 2.579 2.305 2.316 2.319

Air void (%) 3.5 3.5 3.52 3.56 3.86VMA (%) 14.7 14.4 17.1 17.53 17.85VCAmix (%) N.A 35.55 35.58 38.31VCAmix (%) N.A 37.44 38.46 38.72Theoretical maximum

gravity (g/cm3)2.618 2.663 2.492 2.364 2.381

F.M. Nejad et al. / Construction and Buildprocess to develop the optimal gradation and binder content ofSMA mixtures is discussed in another paper [19].coarse and ne aggregates. The properties of coarse and ne aggre-gates are given in Table 1. The bitumen used in SMA and HMA isthe 60/70 penetration bitumen. Results of its properties are listedin Table 2.

3.2. Specimen preparation

HMA specimens were prepared at optimum asphalt contentusing the Marshall Mix design procedure [18]. The optimal grada-tion and binder content of the SMA mixtures are also determinedusing the AASHTO MP8 standard. Furthermore, the ber-stabilizerwas added into the SMA mixture as to improve the mixture perfor-mance and to prevent the binder draindown. The nal resultstain the fatigue life prediction equations of mixtures on specictemperature.

3.1. Materials used

This study included two types of wearing course materials, con-ventional HMA and SMA. The particle size distribution of theaggregates is shown in Fig. 1 for HMA and Fig. 2 for SMA. SMAmix-ture types include type A, B and C with a nominal maximum aggre-gate size of 19, 12.5 and 9.5 mm, respectively and HMA mixturetypes include type H1 and H2 with a NMAS of 9.5 and 12.5 mm,Fig. 1. Aggregate gradation curve of HMA mixtures types H1 and H2 by the NMASof 9.5 mm and 12.5 mm respectively.ing Materials 24 (2010) 11581165 1159Two laboratory tests that were used in this research are theindirect tensile stiffness modulus test and the indirect tensile fati-

gue test which results in a perception of the bituminous materialability for load spreading and its resistance to fatigue cracking.

3.3.1. Indirect tensile stiffness modulus testThe ITSM test [20] was used to determine the tensile properties

of the asphalt concrete which can be further related to the crackingproperties of the pavement. Using the draft version of BS DD 213standard for fatigue behavior characterization, indirect tensilestiffness modulus test was used in order to determine the stiffnessmodulus of the mixtures. Specimens were subjected to a repeateddynamic compressive load across the vertical cross section alongthe depth of the specimen using two loading strips 12.5 mm inwidth. The loading was applied at constant amplitudes of stressfrom 30 to 1000 kPa depending on test temperatures. All materialswere tested at three temperatures (5, 25, and 40 C). The deforma-tion of the specimen was monitored through linear variable differ-ential transducers LVDTs. The LVDTs were clamped vertically onthe diametrical side of the specimen.

3.3.2. Indirect tensile fatigue testThe indirect tensile fatigue test was one of the tests that can

characterize the fatigue behavior of the mixture. The tests wereperformed in controlled stress mode according to the BS DD 213standard. Relationship between tensile stress and number of cycleto failure for each material was established. Linear relationshipwas recorded when log stress is plotted against log cycles to failureand the fatigue life prediction equations were developed. In addi-tion, tensile strains could be determined by using the relationshipbetween stress and stiffness modulus.

4. Test results and discussion

The main objectives of this study were to evaluate the effect ofgradation type, coarseness and neness of gradation, temperatureand asphalt content on fatigue life of hot mix asphalt and stonemastic asphalt specimens at different load magnitudes. To achievethese objectives, HMA specimens with two aggregate gradationsand SMA specimens with three aggregate gradations were pre-pared according to Code 101 standard of Iran Management andProgramming Organization [21] and AASHTO MP8 [22], respec-tively. The prepared specimens were evaluated by performingthe indirect tensile fatigue test using the universal testing machineUTM.

4.1. Indirect stiffness modulus and fatigue life results

The asphalt mixtures stiffness modulus, and fatigue life of spec-imens prepared using different aggregate gradations (H1 and H2gradations for HMA and A, B and C gradations for SMA) were deter-mined at different loading magnitudes (301000 kPa) and differenttemperatures (5, 25 and 40 C). The test results are summarized inTables 4 and 5 for HMA and SMA, respectively. The data shown arethe mean value of two tested specimens for each of the two differ-ent kinds of wearing course mixtures.

The HMAmixtures have the average stiffness signicantly high-er than that of the SMA mixtures at any test temperature. This re-sult is because of the aggregate gradation of HMAmixtures that arecontinuous dense graded and will make the mixture stiffer thanthe gap-graded SMA mixtures [8].

MA

N

49

33

17

12

11

27

12

44

20

16

80

28

150 477 12

44

1160 F.M. Nejad et al. / Construction and Building Materials 24 (2010) 11581165200 467950 13,412

1000 13,529

25 400 2398

500 2200

600 2202

700 1957

800 1768

900 1517

40 100 492Table 4Results of indirect tensile stiffness modulus test and indirect tensile fatigue test for H

Temperature (C) Gradation

HMA type H1 (NMAS:9.5 mm)

Applied stress (kPa) Sm (MPa)

5 800 13,623

850 13,413

900 13,162250 440 23

300 409 1099 500 1906 1224

4 600 1798 603

6 700 1653 404

8 800 1452 170

900 1291 50

14 100 462 2099

24 150 451 914

3 200 422 512mixtures.

HMA type H2 (NMAS:12.5 mm)

f Applied stress (kPa) Sm (MPa) Nf

3,531 800 11,794 422,081

5,471 850 11,824 300,261

2,792 900 11,344 135,224

9,363 950 10,871 98,686

1,764 1000 10,607 67,576

44 400 2107 23285 250 415 158

4 300 396 92

211260797Highlight

Table 5Results of indirect tensile stiffness modulus test and indirect tensile fatigue test for SMA

Temperature (C) Gradation

SMA type A (NMAS:19 mm) SMA type B (N

Applied stress (kPa) Sm (MPa) Nf Applied stress (kPa) Sm (MPa) Nf Applied stress (kPa) Sm (MPa) Nf

5 600 9738 177,781 600

700 9630 147,838 700

800 9533 78,819 800

900 8853 48,303 900

1000 8762 46,412 1000

F.M. Nejad et al. / Construction and Build25 50 1970 37,687 100

100 1565 20,609 200

200 1329 2285 300

300 1087 733 400

400 691 163 500

600

40 10 288 16,242 30Using the regression analysis, the fatigue equations were devel-oped which are in the form of Wohlers fatigue prediction model(Eq. (1)). For every type of the gradation in every three tempera-ture, the fatigue equations are shown in Table 6.

Nf k1 1r k2

1

In Eq. (1), Nf is the number of cycles to failure of the specimen, r isthe applied stress and k1 and k2 are the coefcients related to themixture properties.

30 208 3828 50

50 182 985 75

75 165 323 100

100 147 49 150

200

Table 6Fatigue prediction equations of HMA and SMA mixtures.

Temperature (C) Asphalt type R2 Fatigue equation

5 SMA type A 0.944 Nf = 4 1013r2.989SMA type B 0.958 Nf = 3 1013r2.869SMA type C 0.987 Nf = 1 1024r6.378HMA type H1 0.926 Nf = 2 1026r7.071HMA type H2 0.978 Nf = 3 1030r8.578

25 SMA type A 0.944 Nf = 2 109r2.614SMA type B 0.970 Nf = 3 1012r3.787SMA type C 0.971 Nf = 4 1012r3.647HMA type H1 0.981 Nf = 5 1015r4.684HMA type H2 0.961 Nf = 2 1013r3.823

40 SMA type A 0.910 Nf = 6 106r2.351SMA type B 0.995 Nf = 4 109r3.405SMA type C 0.991 Nf = 1 109r3.021HMA type H1 0.983 Nf = 3 109r2.987989HMA type H2 0.960 Nf = 1 109r2.87910,127 243,813 800 11,741 423,746

10,590 182,639 850 11,482 265,175

10,887 143,423 900 11,346 201,493

10,597 79,159 950 11,379 125,411

10,347 58,261 1000 11,431 104,448

2190 55,429 200 2485 26,140

2155 4969 250 1796 9044

1937 1999 300 2169 4364

1760 544 400 1988 1109

1606 178 500 1812 474

1381 42 600 1630 235

510 36,323 30 618 40,470mixtures.

MAS: 12.5 mm) SMA type C (NMAS: 9.5 mm)

ing Materials 24 (2010) 11581165 1161Using the fatigue prediction equations and the correspondingcoefcients developed for a specic type of asphalt in a particulartemperature, one could compare the fatigue behavior of differentmixtures. Fatigue life of a pavement constructed by a specic as-phalt mixture is affected by different properties of the mixtureincluding type and amount of binder used in the mixture, temper-ature, gradation properties and air void [2,3].

Variations of the k1 and k2 coefcients for SMA and HMA mix-tures are presented in Figs. 3 and 4.

From Figs. 3 and 4, it can be concluded that fatigue life de-creases with increase in temperature. This conrms the previousresearches on this issue [2,3]. Also, it could be seen that, HMA mix-tures generally have greater fatigue lives than SMA mixtures thatmay be because of their aggregate gradation type which includea dense graded structure of aggregates interlocked to each otherin comparison with SMA mixtures by a gap-graded aggregatestructure with stone-on-stone contact.

Also, the fatigue diagrams for SMA and HMA mixtures areshown in Figs. 513. These diagrams are drawn in a way that theresults of the two kinds of mixture by an equal NMAS could becompared in a specic temperature.

4.2. Effects of different parameters on fatigue life

For an appropriate comparison between the fatigue behavior ofHMA and SMA, different affecting parameters of asphalt mixturesshould be correctly considered. In this regard, by considering thevarying and constant parameters in mixtures, the results couldbe analyzed.

496 6598 50 560 9008

448 1335 75 500 2440

391 644 100 473 1133

408 196 150 437 217

370 47 200 384 169

211260797Highlight

uild1162 F.M. Nejad et al. / Construction and BParameters such as gradation type, neness and coarseness ofgradation and the asphalt content could be considered as inuenc-ing factors of fatigue behavior in these series of laboratory tests.However, it should be noted that, the asphalt contents are not con-stant in mixtures. So its effect is considered together with the tem-perature or gradation properties as a constant parameter.

4.2.1. Effect of aggregate type on fatigue lifeConsidering the results of stiffness modulus Sm of bituminous

mixtures (Tables 4 and 5), the HMA mixtures have greater Sm thanSMA mixtures. It should be mentioned that this comparison ismade in mixtures by equal NMASs (e.g. between SMA type C andHMA type H1 by NMAS of 9.5 mm). Thus, it can be found thatthe HMAmixtures should have a greater fatigue life than SMAmix-tures by the same NMAS that could also be drawn from the abovegures.

Fig. 3. Coefcient of k1 in fatigue prediction equation

Fig. 4. Coefcient of k2 in fatigue prediction equationing Materials 24 (2010) 11581165Gap-graded SMA mixtures using stone-on-stone contact, have astructure that makes it greatly rut resistant. This comes from itsstrength against the compressive stresses that is supported by itsstone matrix [2,3,11,19]. It seems that SMA are not capable ofundergoing tensile stresses that will lead to fatigue cracking [8].On the contrary, HMA mixtures with a continuous dense gradedaggregate structure have greater interlocking between the aggre-gates that makes it more resistant to tensile stresses and conse-quently have better fatigue behavior.

4.2.2. Effect of asphalt content and gradation neness and coarsenesson fatigue life

Since all of the mixtures in this study are prepared by the opti-mum air void, increasing the asphalt content will make the mix-ture less stiff and therefore, less fatigue resistant [2]. The resultsshow that the SMA mixtures with greater amount of asphalt con-

for HMA and SMA mixtures in test temperatures.

for HMA and SMA mixtures in test temperatures.

uildF.M. Nejad et al. / Construction and Btent have smaller fatigue lives comparing with the HMA mixtureby the same NMAS.

Considering the effect of asphalt content on fatigue life of SMAmixtures, type C by NMAS of 9.5 mm with the asphalt content per-centage of 6.5% should have a fatigue life less than type B by NMASof 12.5 mm and asphalt content percentage of 5.5%. But the resultsdo not conrm this conclusion. So it can be inferred from the re-sults that the effect of coarseness and neness of aggregate grada-

Fig. 5. Fatigue diagrams of HMA type H1 and SMA type C in 5 C.

Fig. 6. Fatigue diagrams of HMA type H1 and SMA type C in 25 C.

Fig. 7. Fatigue diagrams of HMA type H1 and SMA type C in 40 C.ing Materials 24 (2010) 11581165 1163tion on fatigue behavior is a lot more than the effects of asphaltcontent [1]. Asphalt mixture with ner aggregate gradation willshow a better fatigue behavior than with coarse aggregategradation.

4.2.3. Combined effects on fatigue life comparisonBecause of the same NMAS of 9.5 mm of SMA mixtures type C

and HMA mixtures type H1, they cannot be compared according

Fig. 8. Fatigue diagrams of HMA type H2 and SMA type B in 5 C.

Fig. 9. Fatigue diagrams of HMA type H2 and SMA type B in 25 C.

Fig. 10. Fatigue diagrams of HMA type H2 and SMA type B in 40 C.

uild1164 F.M. Nejad et al. / Construction and Bto the gradation neness and coarseness. Also, because of the sameNMAS of 12.5 mm, SMA mixtures type B and HMA mixtures typeH2 cannot be compared in this respect. The SMA mixtures type Aby NMAS of 19 mm could be compared to both HMA types H1and H2 by the NMASs of 9.5 mm and 12.5 mm, respectively.

dent of the gradation type, asphalt content and other inuenc-

States. USA: National Center for Asphalt Technology Publication; 1992.

Fig. 11. Fatigue diagrams of HMA types H1, H2 and SMA type A in 5 C.

Fig. 12. Fatigue diagrams of HMA types H1, H2 and SMA type A in 25 C.

Fig. 13. Fatigue diagrams of HMA types H1, H2 and SMA type A in 40 C.[6] Karim MR. Fatigue and deformation properties of glass ber reinforcedbituminous mixes. J Eastern Asia Soc Transport Stud 2005;6:997.

[7] Brown ER, Cooley LA. Designing stone matrix asphalt mixtures for rut-resistantpavements. NCHRP Report 425. Washington (DC, USA): TransportationResearch Board, National Research Council; 1999.

[8] Ratnasamy M, Bujang BK. Laboratory diameteral fatigue performance of SMAwith cellulose oil palm ber. Am J Appl Sci 2006;3(9).

[9] Richardson JTG. Stone mastic asphalt in the UK. In: Symposium on stonemastic asphalt and thin surfacing; 1997.

[10] Bellin P. Development, principles and long-term performance of stone masticasphalt in Germany. In: Symposium on stone mastic asphalt and thinsurfacings. SCI Lecture Papers Series. London: Society of Chemical Industry;1997.

[11] Brown ER, Rajib B. Mallick, John E. Haddock, John Bukowski. Performance ofstone matrix asphalt (SMA) mixtures in the United States. In: Proceedings ofthe association of asphalt paving technologists, vol. 66; 1997.

[12] Xue Yongjie, Hou Haobo, Zhu Shujing, Zha Jin. Utilization of municipal solidwaste incineration ash in stone mastic asphalt mixture: pavementperformance and environmental impact. Construct Build Mater2009;23:98996.ing factors in fatigue behavior of asphalt mixtures.2. Stiffness modulus and fatigue life of HMA mixtures are greater

than SMA mixtures with the same nominal maximum aggre-gate size in a specic test temperature that results from the gra-dation type effects on fatigue behavior of asphalt mixtures.

3. An asphalt mixture with ner aggregate gradation has a betterfatigue performance than with coarser aggregate gradation thatis caused by its denser nature.

4. The effects of coarseness and neness of aggregate gradationare greatly more than the effects of asphalt content on fatiguelife of asphalt mixtures.

References

[1] Wen Haang. Fatigue performance evaluation of Westrack asphalt mixturesbased on viscoelastic analysis of indirect tensile test. North Carolina StateUniversity, Department of Civil Engineering; 2001.

[2] NCHRP APPENDIX II-1. Calibration of fatigue cracking models for exiblepavements; 2004.

[3] SHRP A-404. Fatigue response of asphaltaggregate mixer. In: Strategichighway research program. National Research Council; 1994.

[4] Medani TO, Molenaar AAA. Estimation of fatigue characteristics of asphalticmixes using simple tests 2000.

[5] Brown ER. Experiences with stone matrix asphalt in the UnitedComparing with the two types of HMA mixtures, SMA mixturestype A are made of coarser aggregates in addition to its gap-gradedaggregate structures that makes it more vulnerable to fatigue dam-ages. Asphalt mixtures with ner gradation have a better fatiguebehavior because of a better interlocking of the aggregates andmaking a denser mixture [1]. Also, according to the stiffness mod-ulus results (Tables 4 and 5) SMA mixtures type A have smallerstiffness modulus than both HMA mixture types, and it is reason-able that SMA type A have a smaller fatigue life than both HMAmixtures (Figs. 1113).

In addition to the effects of type of gradation and neness andcoarseness of gradation in decreasing the fatigue life of SMA typeA comparing with the HMA types, the percentage of AC 7.8% inSMA type A is also effective in this respect.

5. Conclusions

In this paper a fatigue behavior comparison between SMA andHMA mixtures were presented. The indirect tensile fatigue testingwas carried out and the following conclusions are drawn based onthe comparison performed between the two kinds of mixture:

1. Increasing the temperature will decrease the stiffness modulusand the fatigue life of asphalt mixture. This trend is indepen-

ing Materials 24 (2010) 11581165[13] National Asphalt Pavement Association. Guidelines for materials. Production,and placement of stone matrix asphalt (SMA). Technical Working Group(TWG); 1994 [Publication No. IS 118].

[14] Cooley Jr Allen, Hurley Graham C. Potential of using stone matrix asphalt(SMA) in Mississippi. USA: National Center for Asphalt TechnologyPublication; 2004.

[15] Austroads. Technical note 16: stone mastic asphalt. ARRB TransportationResearch; 2004.

[16] Serfass JP, Samanous J. Fiber-modied asphalt concrete characteristics,application and behavior. J Assoc Asphalt Paving Technol 1996;65:193230.

[17] Sreyya T, Halit O, Atakan A. Investigation of rutting performance of asphaltmixtures containing polymer modiers. Construct Build Mater2007;21(2):32837.

[18] White TD. Marshall procedures for design and quality control of asphaltmixtures. In: Proceedings, association of asphalt paving technologists, vol. 54;1985.

[19] Moghadasnejad F, Mohammadi MA, Aghasoltan A. Dening aneffective gradation for stone mastic asphalt wearing courses. In: Proceedingsof 8th international congress on civil engineering, Shiraz University, Iran;2009.

[20] BS Draft DD 213. Elastic stiffness: method for determination of indirect tensilestiffness of bituminous mixtures; 1993.

[21] Code 101. Standard of iran management and programming organization;2003.

[22] AASHTO MP8. Standard specication for designing stone matrix asphalt(SMA); 2008.

F.M. Nejad et al. / Construction and Building Materials 24 (2010) 11581165 1165

Fatigue behavior of SMA and HMA mixturesIntroductionObjectiveResearch approachMaterials usedSpecimen preparationMethodologyIndirect tensile stiffness modulus testIndirect tensile fatigue test

Test results and discussionIndirect stiffness modulus and fatigue life resultsEffects of different parameters on fatigue lifeEffect of aggregate type on fatigue lifeEffect of asphalt content and gradation fineness and coarseness on fatigue lifeCombined effects on fatigue life comparison

ConclusionsReferences