- Email: [email protected]
Influence of using polymeric aggregate treatment on moisture damage in hot mix asphalt
Construction and Building Materials 47 (2013) 1523–1527
Contents lists available at SciVerse ScienceDirect
Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Influence of using polymeric aggregate treatment on moisture damage in hot mix asphalt F. Moghadas Nejad a, M. Arabani b, Gh.H. Hamedi a,⇑, A.R. Azarhoosh a a b
Department of Civil & Environmental Engineering, Amirkabir University of Technology, Tehran 15875, Iran Department of Civil Engineering, University of Guilan, Rasht, Iran
h i g h l i g h t s Wet samples have lower ITS values in comparison to the ones for dry samples. Use of PE coating in both aggregates causes TSR values to improve significantly. Using PE increases the strength of mixtures against moisture. A significant increase in the ratio of wet/dry stiffness modulus was obtained by PE.
a r t i c l e
i n f o
Article history: Received 29 November 2012 Received in revised form 7 May 2013 Accepted 17 June 2013
Keywords: HMA Moisture damage Polyethylene Indirect tensile strength Indirect tensile stiffness modulus
a b s t r a c t Moisture damage in hot mix asphalt (HMA) occurs due to a loss of adhesion and or cohesion, resulting in the reduced strength or stiffness of the HMA and the development of various forms of pavement distress. One of the convenient approaches to decreasing moisture sensitivity in HMA is coating the aggregate surface with a suitable agent. In this research, the effects of two types of polyethylene (PE), namely high density polyethylene (HDPE) and low density polyethylene (LDPE), on moisture damage of asphalt mixtures were evaluated. Two types of aggregates representing a considerable range in mineralogy (granite and limestone) were evaluated during the course of this study. To assess the impact of PE on moisture damage of HMA, control mixtures (without PE) and mixtures containing PE in dry and wet conditions were tested using indirect tensile strength (ITS) and indirect tensile stiffness modulus (ITSM) tests. The results showed that the ratio of wet/dry values of ITS and ITSM for mixtures containing limestone was higher than those of the samples with granite aggregate. The results of the laboratory tests indicate that PE increases the wettability of asphalt binder over the aggregate and the adhesion between the asphalt binder and aggregate, especially in the mixtures containing acidic (granite) aggregate prone to moisture damage. The aggregates treated with HDPE showed better resistance against moisture damage in both aggregates that were used in this study. Ó 2013 Published by Elsevier Ltd.
1. Introduction Many highway agencies have been experiencing premature failures that diminish the performance and service life of the pavements. One of the major causes of premature pavement failure is the moisture damage of the asphalt mixture layer [1]. The extent of moisture damage, also called moisture susceptibility, depends on internal and external factors. The internal factors are related to the properties of the materials and the microstructure distribution, while the external factors include the environmental conditions, production and construction practices, pavement design, and traffic level [2]. Several mechanisms responsible for adhesion and debonding between the bitumen and aggregate are identified ⇑ Corresponding author. Tel.: +98 9356018017; fax: +98 2517738456. E-mail address: [email protected] (Gh.H. Hamedi). 0950-0618/$ - see front matter Ó 2013 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.conbuildmat.2013.06.060
in the literature. Most of these mechanisms are based on physiochemical interactions between the bitumen and the aggregate, and can be classified into the following three broad categories: (1) mechanical adhesion, (2) physical adhesion, and (3) chemical bonding [3]. Moisture damage is of great negative impacts on asphalt pavement. It exacerbates the service performance (e.g., rutting, cracking) for asphalt mixture under traffic load [4]. Moisture entering from the surface or weakening from the bottom layers of asphalt pavement causes the asphalt film to detach from the aggregate surface or soften the binder through an emulsification process. The weakening resulted from this moisture damage is commonly referred to as stripping because the asphalt film is usually stripped from the aggregate particles [5]. Moisture reduces the internal strength of the HMA mix, the stresses generated by traffic loads increase significantly and lead to fatigue cracking or rutting of
1524
F. Moghadas Nejad et al. / Construction and Building Materials 47 (2013) 1523–1527
the HMA layer. In general, susceptibility of HMA to fatigue and rutting caused by moisture damage are determined by tensile strength tests [6]. Additives have been used for improving the performance of HMA pavements to various distresses. The use of the anti-stripping agent is the most common method to improve the moisture susceptibility of asphalt mixtures [7]. In order to improve adhesion and reduce moisture sensitivity in asphalt mixtures, two general categories of anti-stripping agents become apparent. The first category suggests the aggregate surface to be coated by a suitable agent that will reverse the predominant electrical charges at the surface and thus reduce the surface energy of the aggregate. The second approach is to reduce the surface energy of the binder with suitable agents and give an electrical charge opposite to that of the aggregate surface [8]. 1.1. Literature review Of the many ways to prevent moisture damage in pavements, the use of anti-stripping additives is deemed the most effective. Historically, lime and amines have been used to address stripping in asphalt mixtures [9]. The use of other materials as anti-stripping additives could be beneficial against moisture damage of asphalt mixtures. Wasuidian et al. [10] evaluated the moisture sensitivity of two types of HMA mixtures made with two types of aggregate with and without styrene–butadiene–rubber (SBR) treatment for moisture-induced damage potential. SBR coating altered the aggregate surface from hydrophilic to hydrophobic and thereby increased the wettability of the asphalt binder over the aggregate. Sebaaly et al. [11] examined the resilient modulus and tensile strength properties of the field mixed laboratory compacted samples measured at both wet and dry conditions, and showed that aggregate coating with hydrated lime and polymer (UP5000) exhibited better moisture resistance than the control and mixtures containing liquid anti-stripping agents. In their study, Kim et al. [12] presented an approach to help understand moisture damage mechanisms and to evaluate the effects of moisture damage resisting agents. To this end, various cases of performance testing of HMA samples induced by moisture damage and several fundamental property measurements (stiffness, strength, toughness, and bonding energy) of mixture components were conducted. Testing data and analyses demonstrated that the use of anti-stripping additives contributed to moisture damage resistance due to the synergistic effects of mastic stiffening, toughening, and advanced bonding characteristics at mastic-aggregate interfaces. Moghadas Nejad et al. [6] studied the effects of nanomaterial coating, namely Zycosoil, on the moisture damage of asphalt mixtures. The results of their study showed that aggregate coating with a suitable agent caused an increase in the ratio of wet/dry values of indirect tensile strength and indirect tensile fatigue in treated samples compared to the control mix. In another study, the performance of three anti stripping additives – a lime treated aggregate, an amine treated asphalt and a polymer treated aggregate, was studied by Williams and Miknis [13]. Samples were prepared with the untreated asphalt and aggregate, the treated asphalt with untreated aggregate and untreated asphalt with each treated aggregate. In their research, the observation of the asphalt-aggregate interface before and after freeze-thaw cycling showed that the polymer coated aggregate samples performed better than the amine treated asphalt and lime treated aggregate samples. 2. The statement and objectives of the present study One approach to reduce moisture susceptibility is the use of a coating aggregate treatment system providing a protective barrier
on the aggregate, which repels water and waterproofs the aggregate while providing an improved bonding with the asphalt binder. To this end, effects of PE polymer coating on aggregates were evaluated in this study based on ITS and ITSM tests, with and without PE coating. The specific objectives of this study are to: Study the effect of adding PE on the HMA properties. Evaluate the effect of PE as an anti-stripping agent on the moisture damage of HMA. Evaluating the behavior of HMA mixtures under ITS and ITSM tests in dry and wet conditions with and without PE treated aggregates. Selection of aggregate, asphalt binder and anti-stripping additive systems which are more resistant to the moisture damage.
3. Materials 3.1. Aggregate and asphalt binder Two types of aggregates were evaluated in the study. The two aggregates (limestone and granite) represent a considerable range in mineralogy and an associated degree of stripping. The chemical compositions of the aggregates are listed in Table 1. The physical properties of the two types of aggregates are given in Table 2. The gradation of the aggregates used in the study (mean limits of ASTM specifications for dense aggregate gradation) is given in Table 3. The nominal size of this gradation was 19.0 mm. To characterize the properties of the base asphalt binder, conventional test methods, such as the penetration test, softening point test and ductility were performed. The engineering properties of the asphalt binder are presented in Table 4.
3.2. Additives PE is the most popular plastic in the world. This material is a semi crystalline material with excellent chemical resistance, good fatigue and wear resistance and a wide range of properties. It has a very simple structure. A molecule of PE is a long chain of carbon atoms, with two hydrogen atoms attached to each carbon atom. They are light in weight and provide good resistance to organic solvents with low moisture absorption rates [14]. Two types of PE grades were used in this research. Their properties are shown in Table 5. LDPE offers good corrosion resistance and low moisture permeability. It can be used in applications where corrosion resistance is important, but stiffness, high temperatures, and structural strength are not. HDPE offers excellent impact resistance, light weight, low moisture absorption and high tensile strength [14].
4. Experimental set up and procedure The following tests were performed on each sample in three duplicates. For each aggregate blend and asphalt binder, at least three separate samples were produced to determine the reproducibility of the results.
4.1. Mix design methodology The asphalt mixtures were designed by using the standard Marshal mix design procedure with 75 blows on each side of the cylindrical samples. Samples were compacted and tested by deploying the following standard procedures: the bulk specific gravity (ASTM D2726), the stability and flow test (ASTM D1559), and the maximum theoretical specific gravity (ASTM D2041).
Table 1 Chemical composition of the two types of aggregates. Properties
Limestone
Granite
pH Silicon dioxide, SiO2 (%) R2O3 (Al2O3 + Fe2O3) (%) Aluminum oxide, Al2O3 (%) Ferric oxide, Fe2O3 (%) Magnesium oxide, MgO (%) Calcium oxide, CaO (%)
8.8 3.8 18 1 0.4 1.2 51.3
7.1 68.1 16.2 14.8 1.4 0.8 2.4
1525
F. Moghadas Nejad et al. / Construction and Building Materials 47 (2013) 1523–1527 Table 2 Physical properties of the aggregate. Test
Standard
Specific gravity (coarse agg.) Bulk SSD Apparent Specific gravity (fine agg.) Bulk SSD Apparent Specific gravity (filler) Los Angeles abrasion (%) Flat and elongated particles (%) Sodium sulfate soundness (%) Fine aggregate angularity
ASTM C 127
Limestone
Granite
Specification limit
2.612 2.643 2.659
2.654 2.667 2.692
– – –
2.618 2.633 2.651 2.640 25.6 9.2 2.56 46.65
2.659 2.661 2.688 2.656 19 6.5 1.5 56.3
– – – – Max 45 Max 10 Max 10–20 Min 40
ASTM C 128
ASTM ASTM ASTM ASTM ASTM
D854 C 131 D 4791 C 88 C 1252
Table 3 Gradation of the aggregates used in the study. Sieve (mm) Lower–upper limits Passing (%)
19 100 100
12.5 90–100 88
4.75 44–74 65
Table 4 Results of the experiments conducted on 60/70 penetration grade asphalt binder. Test
Standard
Result
Penetration (100 g, 5 s, 25 °C), 0.1 mm Penetration (200 g, 60 s, 4 °C), 0.1 mm Penetration ratio Ductility (25 °C, 5 cm/min), cm Solubility in trichloroethylene, % Softening point, °C Flash point, °C Loss of heating, % Properties of the TFOT Residue Penetration (100 g, 5 s, 25 °C), 0.1 mm Specific gravity at 25 °C, g/cm3 Viscosity at 135 °C, cSt
ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM
64 23 0.36 112 98.9 51 262 0.75
D5-73 D5-73 D5-73 D113-79 D2042-76 D36-76 D92-78 D1754-78
ASTM D5-73 ASTM D70-76 ASTM D2170-85
60 1.020 158.5
Table 5 Properties of two types of PE. Test 3
Density(g/cm ) Water absorption, 24 h (%) Tensile strength (MPa) Tensile elongation at yield (%)
Standard
LDPE
HDPE
ASTM-D792 ASTM-D570 ASTM-D638 ASTM-D638
0.92 <0.01 13.4 600–650
0.97 0 23.6 820–850
4.2. Sample preparation for ITS and ITSM tests 4.2.1. Preheating Aggregates were heated for 24 h in an oven to dry them to the maximum extent. The binder was kept in an oven for 2 h at an appropriate mixing temperature.
4.2.2. Aggregate coating In the PE coating method, the aggregates are initially mixed with 0.5 percent water. Then the PE is added and mixed with wet aggregate. Due to the moisture on the surface of aggregates, a thin level of PE is formed over them. The amount of added PE to the aggregates is 0.43 and 0.48 percent of their weight for granite and limestone aggregates, respectively. The sufficient temperature of the created mixture for the melting of PE and spreading it over the aggregate surface is 180–190 °C. Since limestone is porous, an amount of melted PE is pervaded over it. Therefore, the amount of usable PE is more in the case of limestone aggregate. To avoid aggregate lumping, the produced mixture is mixed slowly for 5 minutes. In this manner, 80–90 percent of the aggregates surface is covered by PE. In this step, the temperature is decreased to 150–160 °C, a temperature in which the PE coating has been stiff over the surface of aggregates.
2.36 28–58 56
0.3 5–21 40
0.25 2–10 20
0.106 7–18 9
0.075 4–10 6
4.2.3. Mixing In this stage, the aggregate and asphalt binder mixed continuously until the asphalt binder formed a suitable coverage over the aggregate surface. Enough material is mixed to produce at least six specimens of the asphalt binder content recommended for the mixture. Extra mixture will be needed for trials to establish the compaction required and for determining the maximum specific gravity of the mixture, if these values are not known. 4.2.4. Compaction Some experimentation will be needed to find the correct compactive effort that will yield 7 ± 0.5 percent air voids. The mix was compacted by a Marshal hammer to form the samples with the required density and 7 ± 0.5 air voids. 4.2.5. Preconditioning The preconditioning of samples was performed according to the AASHTO T 283 standard method. The specimens are separated into two subsets (conditioned and unconditioned), of at least three specimens each, so that the average air voids of the two subsets are approximately equal. A vacuum is applied to partially saturate conditioned specimens to a level between 55% and 80%. Vacuum-saturated samples are kept in a freezer at 18 °C for 16 hours and then placed in a 60 °C water bath for 24 h. After this period of time, the specimens are considered to be conditioned. The other three samples remain unconditioned [15]. All of the samples are brought to a constant temperature, and ITS and ITSM tests are conducted on both unconditioned (dry) and conditioned (wet) specimens. 4.3. Indirect tensile strength (ITS) test procedure The specimen is removed from the bath, the thickness is determined, and then placed on its side between the bearing plates of the testing machine. Steel loading strips are placed between the specimen and the bearing plates. A load is applied to the specimen by forcing the bearing plates together at a constant rate of 2 in. (50.8 mm) per minute.
S ¼ ð2000PÞ=ðp t DÞ
ð1Þ
where P is the peak value of the applied vertical load (kN), t the mean thickness of the test specimen (m), and D is the specimen diameter (m). The indirect tensile strength ratio (TSR) was determined with the following equation:
TSR ¼ 100ðScond =Suncond Þ
ð2Þ
where Scond is the average indirect tensile strength of the wet specimens, and Suncond is the average indirect tensile strength of the dry specimens. 4.4. Indirect tensile stiffness modulus (ITSM) test procedure Indirect tensile stiffness modulus gives the relationship between stress and strain of asphalt mixtures at specific load and temperature [16]. For each mixture, three samples were subjected to a diametric resilient modulus test at 25 °C, and cylindrical specimens with a diameter and height of 101.6 mm and 65 mm were used, respectively. The test was conducted by applying a compressive load with a
F. Moghadas Nejad et al. / Construction and Building Materials 47 (2013) 1523–1527
haversine waveform (loading = 0.1 s and rest = 0.9 s) on the vertical diametric plane of the cylindrical specimen. The ITSM test is a non-destructive test and was conducted in accordance with recognized guidelines [17]. Namely, two sets of five load pulses were applied to the specimen, and the specimen was rotated by 90° after the first set of loadings. Thus, in the second set of loadings, the load was applied perpendicularly to the direction of the first set. The average stiffness modulus of each set was calculated, and the two values were averaged to obtain the final stiffness modulus [18]. Based on the test data, the resilient modulus was computed according to the following equation:
M R ¼ Pðm þ 0:27Þ=ðt DHÞ
ð3Þ
where P is the repeated load (N), t the specimen thickness (mm), DH the recoverable horizontal deformation (mm), and m is the Poisson ratio. The resilient modulus was determined according to ASTM D4123, and a Poisson ratio of 0.35 was applied.
5. Results and discussion 5.1. Mix design and PE content The optimum asphalt content in the control samples made with limestone and granite aggregates were found to be 5.6% and 5.1%, respectively. It is noteworthy that the mix design was performed with the aggregates without any treatment. 5.2. The results and discussion of the indirect tensile strength (ITS) test
Indirect Tensile Strength (kPa)
As shown in Figs. 1 and 2, the ITS values for each dry and wet sample of a mix with and without PE under dry and wet conditions are compared. It was observed that the ITS values of the wet mixes are lower in comparison with the ones for dry mixes at the end of the loading test. This was expected because the presence of water causes a reduction in asphalt-aggregate adhesion, and thus the strength of asphalt mixture samples decrease under loading. The use of PE is not notable on the ITS of samples in dry condition. What is interesting in this data is that the ITS of the mix with HDPE is higher compared to LDPE and control samples without PE in wet
1600 1400 1200 1000 800 600
conditions. A possible explanation for this might be that HDPE has lower moisture permeability. Fig. 3 showed the unconditioned and moisture conditioned tensile strength TSR properties of the HMA mixtures for two types of aggregates. The TSR of the control mixtures (without PE) containing limestone is greater than those of control mixtures containing granite, which leads to better resistance against moisture damage. Since granite has more SiO2 compared to limestone, this causes a reduction in the bond between asphalt and aggregate in the presence of water. The data also shows that the TSR values are significantly improved with the addition of PE for both aggregates. Most aggregates have electrically charged surfaces (polar surfaces). Asphalt binder, which is composed chiefly of high molecular weight hydrocarbons, exhibits little polar activity; therefore, the bond that develops between asphalt and an aggregate is primarily due to relatively weak dispersion forces. PE treatment alters the aggregate surface by increasing its non-polarity for increased wettability of asphalt on the aggregate. All of the TSR values of the PEtreated mixtures are well above 74%. The addition of HDPE and LDPE in mixtures containing granite resulted in an increase in TSR of 21% and 9%, respectively, compared to the control samples.
5.3. The results and discussion of the indirect tensile stiffness modulus (ITSM) test The stiffness modulus results were determined as shown in Fig. 4. Stiffness modulus is an engineering property that describes the stress–strain relationship of the HMA mix. A reduction in the stiffness modulus property after freeze-thaw cycling leads to an increase in the strain experienced by the HMA mixture due to traffic induced stresses. As the HMA is subjected to higher strain, its
90
Tensile Strength Ratio %
1526
70 60 50 40 30 20 10 0
400
Granite
200 0
80
Control Granite+LDPE
Granite
Conditioned
Granite+HDPE
Unconditioned
Limestone
control Treated with LDPE
control Treated with HDPE
Fig. 3. Unconditioned and conditioned TSR values of samples containing granite and limestone aggregate.
Stiffness Moduluse (MPa)
Indirect Tensile Strength (kPa)
Fig. 1. Unconditioned and conditioned indirect tensile strength in samples containing granite aggregate.
1600 1400 1200 1000 800 600 400 200
1400 1200 1000 800 600 400 200 0
0 Limestone
Limestone+LDPE
Conditioned
Limestone+HDPE
Unconditioned
Fig. 2. Unconditioned and conditioned indirect tensile strength values of samples containing limestone aggregate.
Granite(uncond)
Control
Granite(cond)
Limestone(uncond) Limestone(cond)
Control with LDPE
Control with HDPE
Fig. 4. Unconditioned and conditioned stiffness modulus values of samples containing granite and limestone aggregate.
Resilient Moduluse Ratio %
F. Moghadas Nejad et al. / Construction and Building Materials 47 (2013) 1523–1527
1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Granite
Control
Control with LDPE
Limestone
Control with HDPE
Fig. 5. Unconditioned and conditioned stiffness modulus ratio values of samples containing granite and limestone aggregate.
tendency to experience rutting and fatigue cracking would increase [19]. The results of Table 4 show that mixtures with PE have a higher stiffness modulus than those of the control mixture in wet conditions. This means that the use of PE causes an increase in the strength of the mixtures against moisture. The higher wet stiffness modulus of PE mixtures could be related to the fact that inclusion of PE increases the strength of the mixture due to interlocking phenomenon thus making the mixture more resistant to moisture damage. Interlocking strength has been increased due to penetration of melted PE into the voids of aggregates. That part of PE which has penetrated to the surface voids of aggregates constructs a continuous combination with that part of PE located in the space between an aggregate and other aggregates. Hence, interlocking strength between aggregate and asphalt increases. Such a continuous combination is connected with the surface of aggregate on one side and with the asphalt on the other side. The usage of the aggregate coating does not have notable change in the stiffness modulus of the unconditioned samples. An increase of stiffness modulus in the sample containing HDPE is higher compared to the samples containing LDPE in wet conditions. According to the data presented in Table 5, a possible explanation for this might be that HDPE has more tensile strength. Fig. 5 shows the ratio of wet/dry stiffness modulus for the HMA mixtures treated with two types of PE coating. The data of this figure shows that for the two types of aggregate, the use of PE coating has a significant increase in the stiffness modulus ratio. This increase in stiffness modulus ratio is higher in the samples containing granite aggregate that are prone to moisture damage. In the samples containing limestone aggregate, the use of PE has less improvement in stiffness modulus ratio in comparison to the samples containing granite aggregate. 6. Conclusion This research focused on using a method to decrease moisture sensitivity of asphalt mixtures. In this paper, aggregate coating with a suitable agent was used as a suitable method that obtained a resistance mixture of asphalt binder and aggregate against moisture damage. PE coating altered the aggregate surface from hydrophilic to hydrophobic and thereby increased the wettability of the asphalt binder over the aggregate. The following conclusions can be drawn from the present paper:
1527
Wet samples have lower ITS values in comparison to the ones for dry samples at the end of the loading test. In wet conditions, ITS values in the mixtures treated with HDPE are higher compared to LDPE and the control samples without PE. Use of PE coating in both aggregates causes TSR values to improve significantly, especially in the case of granite aggregate. Using PE increases the strength of mixtures against moisture by increasing the stiffness modulus of samples in wet conditions. In samples containing granite aggregate that are prone to moisture damage, a significant increase in the ratio of wet/dry stiffness modulus was obtained by using PE coating.
References [1] Sengoz B, Agar E. Effect of asphalt film thickness on the moisture sensitivity characteristics of hot mix asphalt. Build Environ J 2007;42:3621–8. [2] Mercado AE. Influence of fundamental material properties and air void structure on moisture damage of asphalt mixes, Ph.D. thesis, A&M University, Texas; 2007. [3] Bhasin A. Development of method to quantify bitumen-aggregate adhesion and loss of adhesion due to moisture. PhD thesis, A&M University, Texas; 2006. [4] Xie J, Wu S, Pang L, Lin Juntao, Zhu Z. Influence of surface treated fly ash with coupling agent on asphalt mixture moisture damage. Constr Build Mater 2012;42:340–6. [5] Chen X, Huang B. Evaluation of moisture damage in hot mix asphalt using simple performance and superpave indirect tensile tests. Constr Build Mater 2008;22:1950–62. [6] Moghadas Nejad F, Azarhoosh AR, Hamedi GhH, Azarhoosh A. Influence of using nonmaterial to reduce the moisture susceptibility of hotmix asphalt. Constr Build Mater 2012;31:384–8. [7] Vural Kok B, Yilmaz M. The effects of using lime and styrene–butadiene– styrene on moisture sensitivity resistance of hot mix asphalt. Constr Build Mater 2009;23:1999–2006. [8] Aksoy A, Samlioglu K, Tayfur S, Ozen H. Effect of various additives on moisture damage sensitivity of asphalt mixtures. Constr Build Mater 2005;19:11–8. [9] Yoon HH, Tarrer AR. Effect of Aggregate Properties on Stripping. Transportation Research Record Report No. 1171. Transportation Research Board, National Research Council, Washington DC; 1988. p. 37–43. [10] Wasiuddin NM, Zaman MM, O’Rear EA. Effect of polymeric aggregate treatment using styrene butadiene rubber (SBR) for moisture-induced damage potential. In: Transportation Research Board, 86th Annual Meeting, Washington DC, 2007. [11] Sebaaly PE, Tohme P, Hajj EY, Johnston D. Effectiveness of antistrip additives for bituminous mixtures. Int J Pavements 2004;3:1–7. [12] Kim YR, Lutif JS, Bhasin A, Little DN. Evaluation of moisture damage mechanisms and effects of hydrated lime in asphalt mixtures through measurements of mixture component properties and performance testing. J Mater Civ Eng 2008;20:659–67. [13] Williams TM, Miknis FP. The effect of anti-strip treatments on asphaltaggregate systems: an environemental scanning electron microscope study. J Elastomers Plast 1998;30:282–95. [14] Awwad MT, Shbeeb L. The use of polyethylene in hot asphalt mixtures. Am J Appl Sci 2007;4:390–6. [15] American association of state highways and transportation officials. Resistance of compacted bituminous mixture to moisture induced damage AASHTO T283-99, USA; 2000. [16] Moghaddam TB, Karim MR, Sysammum T. Dynamic properties of stone mastic asphalt mixtures containing waste plastic bottles. Constr Build Mater 2012;34:236–42. [17] British Standards Institution BSI. Method for determination of the indirect tensile stiffness modulus of bituminous mixtures, Draft for Development Report. No. 213, London; 1993. [18] Arabani M, Azarhoosh AR. The effect of recycled concrete aggregate and steel slag on the dynamic properties of asphalt mixtures. Constr Build Mater 2012;35:1–7. [19] Little DN, Epps JA. The benefits of hydrated lime in hot mix asphalt. Arlington (VA): Report prepared for National Lime Association; 2006.
Contents lists available at SciVerse ScienceDirect
Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Influence of using polymeric aggregate treatment on moisture damage in hot mix asphalt F. Moghadas Nejad a, M. Arabani b, Gh.H. Hamedi a,⇑, A.R. Azarhoosh a a b
Department of Civil & Environmental Engineering, Amirkabir University of Technology, Tehran 15875, Iran Department of Civil Engineering, University of Guilan, Rasht, Iran
h i g h l i g h t s Wet samples have lower ITS values in comparison to the ones for dry samples. Use of PE coating in both aggregates causes TSR values to improve significantly. Using PE increases the strength of mixtures against moisture. A significant increase in the ratio of wet/dry stiffness modulus was obtained by PE.
a r t i c l e
i n f o
Article history: Received 29 November 2012 Received in revised form 7 May 2013 Accepted 17 June 2013
Keywords: HMA Moisture damage Polyethylene Indirect tensile strength Indirect tensile stiffness modulus
a b s t r a c t Moisture damage in hot mix asphalt (HMA) occurs due to a loss of adhesion and or cohesion, resulting in the reduced strength or stiffness of the HMA and the development of various forms of pavement distress. One of the convenient approaches to decreasing moisture sensitivity in HMA is coating the aggregate surface with a suitable agent. In this research, the effects of two types of polyethylene (PE), namely high density polyethylene (HDPE) and low density polyethylene (LDPE), on moisture damage of asphalt mixtures were evaluated. Two types of aggregates representing a considerable range in mineralogy (granite and limestone) were evaluated during the course of this study. To assess the impact of PE on moisture damage of HMA, control mixtures (without PE) and mixtures containing PE in dry and wet conditions were tested using indirect tensile strength (ITS) and indirect tensile stiffness modulus (ITSM) tests. The results showed that the ratio of wet/dry values of ITS and ITSM for mixtures containing limestone was higher than those of the samples with granite aggregate. The results of the laboratory tests indicate that PE increases the wettability of asphalt binder over the aggregate and the adhesion between the asphalt binder and aggregate, especially in the mixtures containing acidic (granite) aggregate prone to moisture damage. The aggregates treated with HDPE showed better resistance against moisture damage in both aggregates that were used in this study. Ó 2013 Published by Elsevier Ltd.
1. Introduction Many highway agencies have been experiencing premature failures that diminish the performance and service life of the pavements. One of the major causes of premature pavement failure is the moisture damage of the asphalt mixture layer [1]. The extent of moisture damage, also called moisture susceptibility, depends on internal and external factors. The internal factors are related to the properties of the materials and the microstructure distribution, while the external factors include the environmental conditions, production and construction practices, pavement design, and traffic level [2]. Several mechanisms responsible for adhesion and debonding between the bitumen and aggregate are identified ⇑ Corresponding author. Tel.: +98 9356018017; fax: +98 2517738456. E-mail address: [email protected] (Gh.H. Hamedi). 0950-0618/$ - see front matter Ó 2013 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.conbuildmat.2013.06.060
in the literature. Most of these mechanisms are based on physiochemical interactions between the bitumen and the aggregate, and can be classified into the following three broad categories: (1) mechanical adhesion, (2) physical adhesion, and (3) chemical bonding [3]. Moisture damage is of great negative impacts on asphalt pavement. It exacerbates the service performance (e.g., rutting, cracking) for asphalt mixture under traffic load [4]. Moisture entering from the surface or weakening from the bottom layers of asphalt pavement causes the asphalt film to detach from the aggregate surface or soften the binder through an emulsification process. The weakening resulted from this moisture damage is commonly referred to as stripping because the asphalt film is usually stripped from the aggregate particles [5]. Moisture reduces the internal strength of the HMA mix, the stresses generated by traffic loads increase significantly and lead to fatigue cracking or rutting of
1524
F. Moghadas Nejad et al. / Construction and Building Materials 47 (2013) 1523–1527
the HMA layer. In general, susceptibility of HMA to fatigue and rutting caused by moisture damage are determined by tensile strength tests [6]. Additives have been used for improving the performance of HMA pavements to various distresses. The use of the anti-stripping agent is the most common method to improve the moisture susceptibility of asphalt mixtures [7]. In order to improve adhesion and reduce moisture sensitivity in asphalt mixtures, two general categories of anti-stripping agents become apparent. The first category suggests the aggregate surface to be coated by a suitable agent that will reverse the predominant electrical charges at the surface and thus reduce the surface energy of the aggregate. The second approach is to reduce the surface energy of the binder with suitable agents and give an electrical charge opposite to that of the aggregate surface [8]. 1.1. Literature review Of the many ways to prevent moisture damage in pavements, the use of anti-stripping additives is deemed the most effective. Historically, lime and amines have been used to address stripping in asphalt mixtures [9]. The use of other materials as anti-stripping additives could be beneficial against moisture damage of asphalt mixtures. Wasuidian et al. [10] evaluated the moisture sensitivity of two types of HMA mixtures made with two types of aggregate with and without styrene–butadiene–rubber (SBR) treatment for moisture-induced damage potential. SBR coating altered the aggregate surface from hydrophilic to hydrophobic and thereby increased the wettability of the asphalt binder over the aggregate. Sebaaly et al. [11] examined the resilient modulus and tensile strength properties of the field mixed laboratory compacted samples measured at both wet and dry conditions, and showed that aggregate coating with hydrated lime and polymer (UP5000) exhibited better moisture resistance than the control and mixtures containing liquid anti-stripping agents. In their study, Kim et al. [12] presented an approach to help understand moisture damage mechanisms and to evaluate the effects of moisture damage resisting agents. To this end, various cases of performance testing of HMA samples induced by moisture damage and several fundamental property measurements (stiffness, strength, toughness, and bonding energy) of mixture components were conducted. Testing data and analyses demonstrated that the use of anti-stripping additives contributed to moisture damage resistance due to the synergistic effects of mastic stiffening, toughening, and advanced bonding characteristics at mastic-aggregate interfaces. Moghadas Nejad et al. [6] studied the effects of nanomaterial coating, namely Zycosoil, on the moisture damage of asphalt mixtures. The results of their study showed that aggregate coating with a suitable agent caused an increase in the ratio of wet/dry values of indirect tensile strength and indirect tensile fatigue in treated samples compared to the control mix. In another study, the performance of three anti stripping additives – a lime treated aggregate, an amine treated asphalt and a polymer treated aggregate, was studied by Williams and Miknis [13]. Samples were prepared with the untreated asphalt and aggregate, the treated asphalt with untreated aggregate and untreated asphalt with each treated aggregate. In their research, the observation of the asphalt-aggregate interface before and after freeze-thaw cycling showed that the polymer coated aggregate samples performed better than the amine treated asphalt and lime treated aggregate samples. 2. The statement and objectives of the present study One approach to reduce moisture susceptibility is the use of a coating aggregate treatment system providing a protective barrier
on the aggregate, which repels water and waterproofs the aggregate while providing an improved bonding with the asphalt binder. To this end, effects of PE polymer coating on aggregates were evaluated in this study based on ITS and ITSM tests, with and without PE coating. The specific objectives of this study are to: Study the effect of adding PE on the HMA properties. Evaluate the effect of PE as an anti-stripping agent on the moisture damage of HMA. Evaluating the behavior of HMA mixtures under ITS and ITSM tests in dry and wet conditions with and without PE treated aggregates. Selection of aggregate, asphalt binder and anti-stripping additive systems which are more resistant to the moisture damage.
3. Materials 3.1. Aggregate and asphalt binder Two types of aggregates were evaluated in the study. The two aggregates (limestone and granite) represent a considerable range in mineralogy and an associated degree of stripping. The chemical compositions of the aggregates are listed in Table 1. The physical properties of the two types of aggregates are given in Table 2. The gradation of the aggregates used in the study (mean limits of ASTM specifications for dense aggregate gradation) is given in Table 3. The nominal size of this gradation was 19.0 mm. To characterize the properties of the base asphalt binder, conventional test methods, such as the penetration test, softening point test and ductility were performed. The engineering properties of the asphalt binder are presented in Table 4.
3.2. Additives PE is the most popular plastic in the world. This material is a semi crystalline material with excellent chemical resistance, good fatigue and wear resistance and a wide range of properties. It has a very simple structure. A molecule of PE is a long chain of carbon atoms, with two hydrogen atoms attached to each carbon atom. They are light in weight and provide good resistance to organic solvents with low moisture absorption rates [14]. Two types of PE grades were used in this research. Their properties are shown in Table 5. LDPE offers good corrosion resistance and low moisture permeability. It can be used in applications where corrosion resistance is important, but stiffness, high temperatures, and structural strength are not. HDPE offers excellent impact resistance, light weight, low moisture absorption and high tensile strength [14].
4. Experimental set up and procedure The following tests were performed on each sample in three duplicates. For each aggregate blend and asphalt binder, at least three separate samples were produced to determine the reproducibility of the results.
4.1. Mix design methodology The asphalt mixtures were designed by using the standard Marshal mix design procedure with 75 blows on each side of the cylindrical samples. Samples were compacted and tested by deploying the following standard procedures: the bulk specific gravity (ASTM D2726), the stability and flow test (ASTM D1559), and the maximum theoretical specific gravity (ASTM D2041).
Table 1 Chemical composition of the two types of aggregates. Properties
Limestone
Granite
pH Silicon dioxide, SiO2 (%) R2O3 (Al2O3 + Fe2O3) (%) Aluminum oxide, Al2O3 (%) Ferric oxide, Fe2O3 (%) Magnesium oxide, MgO (%) Calcium oxide, CaO (%)
8.8 3.8 18 1 0.4 1.2 51.3
7.1 68.1 16.2 14.8 1.4 0.8 2.4
1525
F. Moghadas Nejad et al. / Construction and Building Materials 47 (2013) 1523–1527 Table 2 Physical properties of the aggregate. Test
Standard
Specific gravity (coarse agg.) Bulk SSD Apparent Specific gravity (fine agg.) Bulk SSD Apparent Specific gravity (filler) Los Angeles abrasion (%) Flat and elongated particles (%) Sodium sulfate soundness (%) Fine aggregate angularity
ASTM C 127
Limestone
Granite
Specification limit
2.612 2.643 2.659
2.654 2.667 2.692
– – –
2.618 2.633 2.651 2.640 25.6 9.2 2.56 46.65
2.659 2.661 2.688 2.656 19 6.5 1.5 56.3
– – – – Max 45 Max 10 Max 10–20 Min 40
ASTM C 128
ASTM ASTM ASTM ASTM ASTM
D854 C 131 D 4791 C 88 C 1252
Table 3 Gradation of the aggregates used in the study. Sieve (mm) Lower–upper limits Passing (%)
19 100 100
12.5 90–100 88
4.75 44–74 65
Table 4 Results of the experiments conducted on 60/70 penetration grade asphalt binder. Test
Standard
Result
Penetration (100 g, 5 s, 25 °C), 0.1 mm Penetration (200 g, 60 s, 4 °C), 0.1 mm Penetration ratio Ductility (25 °C, 5 cm/min), cm Solubility in trichloroethylene, % Softening point, °C Flash point, °C Loss of heating, % Properties of the TFOT Residue Penetration (100 g, 5 s, 25 °C), 0.1 mm Specific gravity at 25 °C, g/cm3 Viscosity at 135 °C, cSt
ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM
64 23 0.36 112 98.9 51 262 0.75
D5-73 D5-73 D5-73 D113-79 D2042-76 D36-76 D92-78 D1754-78
ASTM D5-73 ASTM D70-76 ASTM D2170-85
60 1.020 158.5
Table 5 Properties of two types of PE. Test 3
Density(g/cm ) Water absorption, 24 h (%) Tensile strength (MPa) Tensile elongation at yield (%)
Standard
LDPE
HDPE
ASTM-D792 ASTM-D570 ASTM-D638 ASTM-D638
0.92 <0.01 13.4 600–650
0.97 0 23.6 820–850
4.2. Sample preparation for ITS and ITSM tests 4.2.1. Preheating Aggregates were heated for 24 h in an oven to dry them to the maximum extent. The binder was kept in an oven for 2 h at an appropriate mixing temperature.
4.2.2. Aggregate coating In the PE coating method, the aggregates are initially mixed with 0.5 percent water. Then the PE is added and mixed with wet aggregate. Due to the moisture on the surface of aggregates, a thin level of PE is formed over them. The amount of added PE to the aggregates is 0.43 and 0.48 percent of their weight for granite and limestone aggregates, respectively. The sufficient temperature of the created mixture for the melting of PE and spreading it over the aggregate surface is 180–190 °C. Since limestone is porous, an amount of melted PE is pervaded over it. Therefore, the amount of usable PE is more in the case of limestone aggregate. To avoid aggregate lumping, the produced mixture is mixed slowly for 5 minutes. In this manner, 80–90 percent of the aggregates surface is covered by PE. In this step, the temperature is decreased to 150–160 °C, a temperature in which the PE coating has been stiff over the surface of aggregates.
2.36 28–58 56
0.3 5–21 40
0.25 2–10 20
0.106 7–18 9
0.075 4–10 6
4.2.3. Mixing In this stage, the aggregate and asphalt binder mixed continuously until the asphalt binder formed a suitable coverage over the aggregate surface. Enough material is mixed to produce at least six specimens of the asphalt binder content recommended for the mixture. Extra mixture will be needed for trials to establish the compaction required and for determining the maximum specific gravity of the mixture, if these values are not known. 4.2.4. Compaction Some experimentation will be needed to find the correct compactive effort that will yield 7 ± 0.5 percent air voids. The mix was compacted by a Marshal hammer to form the samples with the required density and 7 ± 0.5 air voids. 4.2.5. Preconditioning The preconditioning of samples was performed according to the AASHTO T 283 standard method. The specimens are separated into two subsets (conditioned and unconditioned), of at least three specimens each, so that the average air voids of the two subsets are approximately equal. A vacuum is applied to partially saturate conditioned specimens to a level between 55% and 80%. Vacuum-saturated samples are kept in a freezer at 18 °C for 16 hours and then placed in a 60 °C water bath for 24 h. After this period of time, the specimens are considered to be conditioned. The other three samples remain unconditioned [15]. All of the samples are brought to a constant temperature, and ITS and ITSM tests are conducted on both unconditioned (dry) and conditioned (wet) specimens. 4.3. Indirect tensile strength (ITS) test procedure The specimen is removed from the bath, the thickness is determined, and then placed on its side between the bearing plates of the testing machine. Steel loading strips are placed between the specimen and the bearing plates. A load is applied to the specimen by forcing the bearing plates together at a constant rate of 2 in. (50.8 mm) per minute.
S ¼ ð2000PÞ=ðp t DÞ
ð1Þ
where P is the peak value of the applied vertical load (kN), t the mean thickness of the test specimen (m), and D is the specimen diameter (m). The indirect tensile strength ratio (TSR) was determined with the following equation:
TSR ¼ 100ðScond =Suncond Þ
ð2Þ
where Scond is the average indirect tensile strength of the wet specimens, and Suncond is the average indirect tensile strength of the dry specimens. 4.4. Indirect tensile stiffness modulus (ITSM) test procedure Indirect tensile stiffness modulus gives the relationship between stress and strain of asphalt mixtures at specific load and temperature [16]. For each mixture, three samples were subjected to a diametric resilient modulus test at 25 °C, and cylindrical specimens with a diameter and height of 101.6 mm and 65 mm were used, respectively. The test was conducted by applying a compressive load with a
F. Moghadas Nejad et al. / Construction and Building Materials 47 (2013) 1523–1527
haversine waveform (loading = 0.1 s and rest = 0.9 s) on the vertical diametric plane of the cylindrical specimen. The ITSM test is a non-destructive test and was conducted in accordance with recognized guidelines [17]. Namely, two sets of five load pulses were applied to the specimen, and the specimen was rotated by 90° after the first set of loadings. Thus, in the second set of loadings, the load was applied perpendicularly to the direction of the first set. The average stiffness modulus of each set was calculated, and the two values were averaged to obtain the final stiffness modulus [18]. Based on the test data, the resilient modulus was computed according to the following equation:
M R ¼ Pðm þ 0:27Þ=ðt DHÞ
ð3Þ
where P is the repeated load (N), t the specimen thickness (mm), DH the recoverable horizontal deformation (mm), and m is the Poisson ratio. The resilient modulus was determined according to ASTM D4123, and a Poisson ratio of 0.35 was applied.
5. Results and discussion 5.1. Mix design and PE content The optimum asphalt content in the control samples made with limestone and granite aggregates were found to be 5.6% and 5.1%, respectively. It is noteworthy that the mix design was performed with the aggregates without any treatment. 5.2. The results and discussion of the indirect tensile strength (ITS) test
Indirect Tensile Strength (kPa)
As shown in Figs. 1 and 2, the ITS values for each dry and wet sample of a mix with and without PE under dry and wet conditions are compared. It was observed that the ITS values of the wet mixes are lower in comparison with the ones for dry mixes at the end of the loading test. This was expected because the presence of water causes a reduction in asphalt-aggregate adhesion, and thus the strength of asphalt mixture samples decrease under loading. The use of PE is not notable on the ITS of samples in dry condition. What is interesting in this data is that the ITS of the mix with HDPE is higher compared to LDPE and control samples without PE in wet
1600 1400 1200 1000 800 600
conditions. A possible explanation for this might be that HDPE has lower moisture permeability. Fig. 3 showed the unconditioned and moisture conditioned tensile strength TSR properties of the HMA mixtures for two types of aggregates. The TSR of the control mixtures (without PE) containing limestone is greater than those of control mixtures containing granite, which leads to better resistance against moisture damage. Since granite has more SiO2 compared to limestone, this causes a reduction in the bond between asphalt and aggregate in the presence of water. The data also shows that the TSR values are significantly improved with the addition of PE for both aggregates. Most aggregates have electrically charged surfaces (polar surfaces). Asphalt binder, which is composed chiefly of high molecular weight hydrocarbons, exhibits little polar activity; therefore, the bond that develops between asphalt and an aggregate is primarily due to relatively weak dispersion forces. PE treatment alters the aggregate surface by increasing its non-polarity for increased wettability of asphalt on the aggregate. All of the TSR values of the PEtreated mixtures are well above 74%. The addition of HDPE and LDPE in mixtures containing granite resulted in an increase in TSR of 21% and 9%, respectively, compared to the control samples.
5.3. The results and discussion of the indirect tensile stiffness modulus (ITSM) test The stiffness modulus results were determined as shown in Fig. 4. Stiffness modulus is an engineering property that describes the stress–strain relationship of the HMA mix. A reduction in the stiffness modulus property after freeze-thaw cycling leads to an increase in the strain experienced by the HMA mixture due to traffic induced stresses. As the HMA is subjected to higher strain, its
90
Tensile Strength Ratio %
1526
70 60 50 40 30 20 10 0
400
Granite
200 0
80
Control Granite+LDPE
Granite
Conditioned
Granite+HDPE
Unconditioned
Limestone
control Treated with LDPE
control Treated with HDPE
Fig. 3. Unconditioned and conditioned TSR values of samples containing granite and limestone aggregate.
Stiffness Moduluse (MPa)
Indirect Tensile Strength (kPa)
Fig. 1. Unconditioned and conditioned indirect tensile strength in samples containing granite aggregate.
1600 1400 1200 1000 800 600 400 200
1400 1200 1000 800 600 400 200 0
0 Limestone
Limestone+LDPE
Conditioned
Limestone+HDPE
Unconditioned
Fig. 2. Unconditioned and conditioned indirect tensile strength values of samples containing limestone aggregate.
Granite(uncond)
Control
Granite(cond)
Limestone(uncond) Limestone(cond)
Control with LDPE
Control with HDPE
Fig. 4. Unconditioned and conditioned stiffness modulus values of samples containing granite and limestone aggregate.
Resilient Moduluse Ratio %
F. Moghadas Nejad et al. / Construction and Building Materials 47 (2013) 1523–1527
1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Granite
Control
Control with LDPE
Limestone
Control with HDPE
Fig. 5. Unconditioned and conditioned stiffness modulus ratio values of samples containing granite and limestone aggregate.
tendency to experience rutting and fatigue cracking would increase [19]. The results of Table 4 show that mixtures with PE have a higher stiffness modulus than those of the control mixture in wet conditions. This means that the use of PE causes an increase in the strength of the mixtures against moisture. The higher wet stiffness modulus of PE mixtures could be related to the fact that inclusion of PE increases the strength of the mixture due to interlocking phenomenon thus making the mixture more resistant to moisture damage. Interlocking strength has been increased due to penetration of melted PE into the voids of aggregates. That part of PE which has penetrated to the surface voids of aggregates constructs a continuous combination with that part of PE located in the space between an aggregate and other aggregates. Hence, interlocking strength between aggregate and asphalt increases. Such a continuous combination is connected with the surface of aggregate on one side and with the asphalt on the other side. The usage of the aggregate coating does not have notable change in the stiffness modulus of the unconditioned samples. An increase of stiffness modulus in the sample containing HDPE is higher compared to the samples containing LDPE in wet conditions. According to the data presented in Table 5, a possible explanation for this might be that HDPE has more tensile strength. Fig. 5 shows the ratio of wet/dry stiffness modulus for the HMA mixtures treated with two types of PE coating. The data of this figure shows that for the two types of aggregate, the use of PE coating has a significant increase in the stiffness modulus ratio. This increase in stiffness modulus ratio is higher in the samples containing granite aggregate that are prone to moisture damage. In the samples containing limestone aggregate, the use of PE has less improvement in stiffness modulus ratio in comparison to the samples containing granite aggregate. 6. Conclusion This research focused on using a method to decrease moisture sensitivity of asphalt mixtures. In this paper, aggregate coating with a suitable agent was used as a suitable method that obtained a resistance mixture of asphalt binder and aggregate against moisture damage. PE coating altered the aggregate surface from hydrophilic to hydrophobic and thereby increased the wettability of the asphalt binder over the aggregate. The following conclusions can be drawn from the present paper:
1527
Wet samples have lower ITS values in comparison to the ones for dry samples at the end of the loading test. In wet conditions, ITS values in the mixtures treated with HDPE are higher compared to LDPE and the control samples without PE. Use of PE coating in both aggregates causes TSR values to improve significantly, especially in the case of granite aggregate. Using PE increases the strength of mixtures against moisture by increasing the stiffness modulus of samples in wet conditions. In samples containing granite aggregate that are prone to moisture damage, a significant increase in the ratio of wet/dry stiffness modulus was obtained by using PE coating.
References [1] Sengoz B, Agar E. Effect of asphalt film thickness on the moisture sensitivity characteristics of hot mix asphalt. Build Environ J 2007;42:3621–8. [2] Mercado AE. Influence of fundamental material properties and air void structure on moisture damage of asphalt mixes, Ph.D. thesis, A&M University, Texas; 2007. [3] Bhasin A. Development of method to quantify bitumen-aggregate adhesion and loss of adhesion due to moisture. PhD thesis, A&M University, Texas; 2006. [4] Xie J, Wu S, Pang L, Lin Juntao, Zhu Z. Influence of surface treated fly ash with coupling agent on asphalt mixture moisture damage. Constr Build Mater 2012;42:340–6. [5] Chen X, Huang B. Evaluation of moisture damage in hot mix asphalt using simple performance and superpave indirect tensile tests. Constr Build Mater 2008;22:1950–62. [6] Moghadas Nejad F, Azarhoosh AR, Hamedi GhH, Azarhoosh A. Influence of using nonmaterial to reduce the moisture susceptibility of hotmix asphalt. Constr Build Mater 2012;31:384–8. [7] Vural Kok B, Yilmaz M. The effects of using lime and styrene–butadiene– styrene on moisture sensitivity resistance of hot mix asphalt. Constr Build Mater 2009;23:1999–2006. [8] Aksoy A, Samlioglu K, Tayfur S, Ozen H. Effect of various additives on moisture damage sensitivity of asphalt mixtures. Constr Build Mater 2005;19:11–8. [9] Yoon HH, Tarrer AR. Effect of Aggregate Properties on Stripping. Transportation Research Record Report No. 1171. Transportation Research Board, National Research Council, Washington DC; 1988. p. 37–43. [10] Wasiuddin NM, Zaman MM, O’Rear EA. Effect of polymeric aggregate treatment using styrene butadiene rubber (SBR) for moisture-induced damage potential. In: Transportation Research Board, 86th Annual Meeting, Washington DC, 2007. [11] Sebaaly PE, Tohme P, Hajj EY, Johnston D. Effectiveness of antistrip additives for bituminous mixtures. Int J Pavements 2004;3:1–7. [12] Kim YR, Lutif JS, Bhasin A, Little DN. Evaluation of moisture damage mechanisms and effects of hydrated lime in asphalt mixtures through measurements of mixture component properties and performance testing. J Mater Civ Eng 2008;20:659–67. [13] Williams TM, Miknis FP. The effect of anti-strip treatments on asphaltaggregate systems: an environemental scanning electron microscope study. J Elastomers Plast 1998;30:282–95. [14] Awwad MT, Shbeeb L. The use of polyethylene in hot asphalt mixtures. Am J Appl Sci 2007;4:390–6. [15] American association of state highways and transportation officials. Resistance of compacted bituminous mixture to moisture induced damage AASHTO T283-99, USA; 2000. [16] Moghaddam TB, Karim MR, Sysammum T. Dynamic properties of stone mastic asphalt mixtures containing waste plastic bottles. Constr Build Mater 2012;34:236–42. [17] British Standards Institution BSI. Method for determination of the indirect tensile stiffness modulus of bituminous mixtures, Draft for Development Report. No. 213, London; 1993. [18] Arabani M, Azarhoosh AR. The effect of recycled concrete aggregate and steel slag on the dynamic properties of asphalt mixtures. Constr Build Mater 2012;35:1–7. [19] Little DN, Epps JA. The benefits of hydrated lime in hot mix asphalt. Arlington (VA): Report prepared for National Lime Association; 2006.