Starch as a modifier for asphalt paving materials

This paper investigates the viability of using starch (ST) as a new modifier for asphalt paving materials. Different ratios of ST (2.5, 5.0, and 7.5% by weight of asphalt) were blended with 70/100 paving grade asphalt. Unmodified and modified asphalt binders were subjected to physicochemical, alkali, acid and fuel resistance tests. The performance tests including, Marshall stability, Marshall Quotient (MQ), tensile strength, tensile strength ratio, flexural strength, rutting resistance and resilient modulus (MR) were carried out on unmodified and modified stone matrix asphalt (SMA) mixtures. The analyses of test results show that the performance of ST-modified asphalt mixtures are better than conventional and styrene–butadiene–styrene (SBS)-modified mixtures. The rutting potential, moisture susceptibility and temperature susceptibility can be reduced by the inclusion of ST in the asphalt mixture. The laboratory MR values are lower than the calculated ones using the empirical equations. The results also revealed that this modifier can be used as anti-stripping agent. It also shows resistance to fuels and most common chemicals. A ST content of 5% by weight of asphalt is recommended for the improvement of the performance of asphalt concrete mixtures similar to that investigated in this study.     

Laboratory comparison study for the use of stone matrix asphalt in hot weather climates

Stone matrix asphalt (SMA) is a hot mixture asphalt consisting of a coarse aggregate skeleton and a high binder content mortar. It was developed in Germany during the mid-1960s and it has been used in Europe for more than 20 years to provide better rutting resistance and to resist studded tyre wear. The main objective of this research study was to compare the performance of the normally used dense graded asphalt mixtures, named in this research as control mixtures, and SMA mixtures. Samples from both mixtures were fabricated at their optimum asphalt contents that were 5.3% for control mixtures and 6.9% for SMA mixtures. Comparison performance tests that included Marshall stability, loss of Marshall stability, split tensile strength, loss of split tensile strength, resilient modulus, fatigue, and rutting testing were performed on both mixtures. Test results showed that although the control mixtures have higher compressive and tensile strengths, SMA mixtures have higher durability and resilience properties. In addition, although the research could not prove the superiority of SMA in rutting resistance because of the limited sample sizes, field performance of SMA mixtures proves its superiority. Therefore, especially in hot weather climates, these properties, (durability, resilience and rutting resistance) give SMA mixtures advantages over dense graded mixtures.     

High temperature properties of wax modified binders and asphalt mixtures

The influence of adding two commercial waxes (FT-paraffin and polyethylene wax) to binders of penetration grades 50/70 and 160/220 were investigated for high temperature performance of binders and asphalt concrete mixtures. Binder properties were determined by conventional test methods, dynamic mechanical analysis and bending beam rheometer testing. The high temperature properties of asphalt concrete were investigated using the French rutting tester.The addition of FT-paraffin and polyethylene wax increased the rutting resistance of mixtures for both types of binder. The FT-paraffin modified asphalt mixtures showed the best rutting resistance.Adding polyethylene wax showed the highest stiffening effect in terms of rutting factor by DMA for the binders. However, this could not be verified in asphalt mixture testing. Adding FT-paraffin improved the rutting resistance of asphalt mixtures containing low or high penetration binder, but for the mixture containing high penetration binder the specification limit was exceeded.     

橡胶-硅藻土复合改性沥青混合料抗水侵蚀性能研究

在前期硅藻精土最佳掺量13％的基础上,在改性沥青中分别复掺0、11％、13％、15％、17％、19％、21％的废橡胶粉,采用旋转压实的方式成型混合料试样,分别进行(浸水)马歇尔试验、冻融劈裂试验和浸水车辙试验.结果表明:当废橡胶粉掺量为17％时,改性沥青混合料的浸水马歇尔残留稳定度达到峰值,冻融劈裂强度比达到最大,较单...     

复合式SMA桥面铺装混合料配比设计及高温抗车辙性能研究

为了提升桥面铺装的高温抗车辙性能,采用马歇尔配合比设计方法对3种SMA沥青混合料分别进行级配设计及体积指标验证,选用轮辙试验和车辙试验对所设计的5种复合式SMA桥面铺装结构组合的高温性能评价指标进行测试.结果表明,SMA混合料沥青析漏损失及飞散损失均满足技术要求,SMA具有合理的最大沥青用量,且粘附性良好;提出的5种复...     

Laboratory evaluation of HMA with high density polyethylene as a modifier

This paper investigates the viability of using high density polyethylene (HDPE) as a modifier for asphalt paving materials. Different ratios of HDPE by weight of asphalt were blended with 80/100 paving grade asphalt. Unmodified and modified asphalt binders were subjected to physicochemical and homogeneity tests. The performance tests including, Marshall Stability, Marshall Quotient (MQ), tensile strength, tensile strength ratio, flexural strength and resilient modulus were carried out on unmodified and modified hot asphalt mixtures. The analyses of test results show that the performance of HDPE-modified asphalt mixtures are better than conventional mixtures. The moisture susceptibility and temperature susceptibility can be reduced by the inclusion of HDPE in the asphalt mixture. A HDPE content of 5% by weight of asphalt is recommended for the improvement of the performance of asphalt concrete mixtures similar to that investigated in this study.     

多次再生沥青混合料沥青组分迁移及其性能

通过室内试验模拟沥青混合料的多次再生过程,探讨了多次再生沥青的物理性质变化特征和组分迁移规律;通过马歇尔试验确定多次再生沥青混合料的配合比,利用单轴贯入强度试验、半圆弯拉试验和冻融劈裂试验对其使用性能进行了评价,并通过沥青混合料性能试验仪(AMPT)分析了其相位角在温度和加载频率同步耦合作用下的变化规律.结果表明:沥青经历多次再生后流变性能变差,高温性能提升,低温性能衰减显著;再生剂在旧沥青中的增溶作用随着其掺量的提高而增强,随着再生次数的增加呈指数规律衰减;再生沥青混合料的高温稳定性随再生次数增加呈对数规律增长,水稳定性对再生次数的敏感度较低,3次再生后其马歇尔体积指标均可满足规范要求;1次再生沥青混合料的动态黏弹特性与全新料较为接近,2次再生后,其弹性效应增强,低温抗裂性能劣化加速.综上所述,沥青混合料经多次再生后,应重点关注其低温性能的恢复情况.     

Utilization of municipal solid waste incineration ash in stone mastic asphalt mixture: Pavement performance and environmental impact

The objective of this study is to the use of municipal solid waste incinerator (MSWI) fly ash as a partial replacement of fine aggregate or mineral filler in stone matrix asphalt (SMA) mixture. For saving natural rock and reusing solid waste, basic oxygen furnace slag (BOF slag) was used as part of coarse aggregate. And this makes SMA mixtures contain more than 90% solid waste materials by mass. A comparative study of the performance of two mixes designed using superior performance asphalt pavements (SUPERPAVE) and Marshall mix design procedures was carried out in this research. Samples from both mixes were prepared at the design asphalt contents and aggregate gradations and were subjected to a comprehensive mechanical evaluation testing. These tests included Marshall stability, water sensibility, resilient modulus, fatigue life and rutting. In all the performed tests SUPERPAVE mixtures proved their superiority over Marshall mixtures. TCLP test for environmental impact indicated that asphalt is an effective stabilization and solidification agent for heavy metal in MSWI ash. The heavy metal leachates in TCLP tests have great positive correlation with their initial concentration in waste. But Ni is an exception that lower initial concentration leaded to higher cumulative leaching rate.     

废玻璃沥青混合料性能的试验研究

将废玻璃用于沥青混合料来铺筑沥青路面,有助于废物利用和环境保护,并对沥青层的表面特征产生一定影响.废玻璃在沥青路面中应用的关键是改善玻璃与沥青的粘附性,试验结果表明,采用高粘度的改性沥青或以水泥作为抗剥落剂可以有效地提高玻璃与沥青的粘附性.掺加一定比例的废玻璃对沥青混合料的设计沥青用量影响不大,但会降低沥青混合料的密度,并使沥青混合料试件的马歇尔稳定度、抗车辙能力和抗滑性略有降低;随着废玻璃用量的增加,沥青层表面的反光性增加.     

密级配沥青混合料沥青膜厚度优选

通过Bailey,Superpave和马歇尔三种方法设计级配,选用六种沥青含量进行了车辙试验,研究了沥青膜厚与车辙动稳定度之间的关系,提出了基于高温性能的密级配沥青混合料沥青膜厚的建议.     

Laboratory comparison of the crumb-rubber and SBS modified bitumen and hot mix asphalt

The use of crumb rubber (CR) recycled from waste tires using an ambient grinding process was evaluated at two stages in asphalt formulation. First, bitumen modified with crumb rubber was evaluated by rotational viscometery (RV), dynamic shear rheometry (DSR) and conventional binder tests. Hot asphalt mixtures including crumb-rubber-modified bitumen were then evaluated by determining the permanent and fatigue characteristics and stiffness moduli of control and modified mixtures. The properties of the crumb-rubber-modified bitumen and asphalt mixtures were compared to different contents of styrene–butadiene–styrene (SBS) modified-bitumen and asphalt mixtures. The tests showed that to achieve the same performance, as with SBS-modification, the CR-content must be used at much higher than SBS. 8%-CR modification was determined as the most suitable content according to both binder and mixture tests.     

Evaluating permanent deformation in asphalt rubber mixtures

Permanent deformation or rutting, one of the most important distresses in flexible pavements, has long been a problem in asphalt mixtures, mainly in countries with high temperatures such as Brazil. Throughout the years, researchers have used different test methods to estimate the rutting performance of asphalt mixtures. One of the alternatives to reduce permanent deformation in asphalt pavement layers is through the use of mixtures produced with asphalt rubber. Crumb rubber from waste tires introduced into the asphalt is one of suitable application to dispose the tires and used as an additive to enhance the properties of the conventional asphalts. This work aims at comparing the rutting performance of asphalt rubber mixtures (with dense and gap-graded aggregate gradation) with the conventional dense graded mixture most used in Brazil. The asphalt rubber mixtures were produced by the wet process using continuous blend and terminal blend asphalt rubber. To study their performance, two laboratory tests, the Repeated Simple Shear Test at Constant Height (RSST-CH) and the Accelerated Pavement Testing Simulator Test (wheel tracking) were carried out. The testing results confirmed that the use of asphalt rubber binder improves significantly the resistance to rutting. The highest resistance is presented by the mixtures produced with continuous blend binders and gap-graded aggregate gradation. The results of both testing apparatus can be correlated by a linear relationship. The testing results allowed concluding that the characteristics of the asphalt rubber binders cannot be used to predict the permanent deformation resistance of the asphalt rubber mixtures.     

沥青掺量对密级配沥青混合料路用性能影响

进行了不同沥青掺量下AC-13C密级配沥青混合料试件的马歇尔稳定度、车辙、冻融劈裂试验,分析了不同沥青掺量对混合料强度特性、高温稳定性、水稳定性的影响。结果表明,利用混合料的抗车辙性能及冻融残留强度两个试验能够合理确定沥青最佳掺量,而马歇尔稳定度试验高估了沥青掺量范围。由此在进行密级配沥青混合料路面结构设计时,抗车辙性能及冻融残留强度应作为确定最佳沥青掺量的主要控制指标,而马歇尔稳定度可作为参考指标,弥补实际操作的不足。     

Study on properties of recycled tire rubber modified asphalt mixtures using dry process

To minimize waste tires pollution and improve properties of asphalt mixtures, properties of recycled tire rubber modified asphalt mixtures using dry process are studied in laboratory. Tests of three types asphalt mixtures containing different rubber content (1%, 2% and 3% by weight of total mix) and a control mixture without rubber were conducted. Based on results of rutting tests (60 °C), indirect tensile tests (−10 °C) and variance analysis, the addition of recycled tire rubber in asphalt mixtures using dry process could improve engineering properties of asphalt mixtures, and the rubber content has a significant effect on the performance of resistance to permanent deformation at high temperature and cracking at low temperature.     

回收料掺量对温拌再生沥青混合料性能的影响

通过室内试验研究了回收沥青混合料(RAP)掺量(质量分数)对Evotherm温拌再生沥青混合料高温稳定性、低温性能、水稳定性及疲劳性能的影响.结果表明:采用Evotherm温拌技术可将RAP掺量提高到50%;温拌再生沥青混合料的高温稳定性、水稳定性及低温性能均随RAP掺量的增加先升后降,且在RAP掺量为30%~40%时出现峰值;疲劳性能随RAP掺量的增加逐渐降低,且应变水平越高降低幅度越大;温拌再生沥青混合料的高温稳定性、水稳定性较热拌再生沥青混合料差,疲劳性能优于热拌再生沥青混合料;在相同RAP掺量下,温拌再生沥青混合料与热拌再生沥青混合料的低温性能相当.     

Performance based binder type selection using mixed integer programming technique

The rationale behind an asphalt mix design is optimizing the binder content for the desired aggregate gradation to satisfy the specified volumetric and strength requirements. The designed asphalt mix should be durable and cost effective. The mechanical behavior of a designed asphalt mix is affected by the traffic loading and climatic variations. To improve the mechanical properties of asphalt mixes, additives are added to the base asphalt binder. These binders are called modified asphalt binders. The objectives of the present study are to compare the performance of asphalt mixes with different binders by two different mix design methods and to optimize the asphalt binder type to achieve the desired performance. Two methods of mix design namely, Marshall and Superpave mix design methods are considered. The performances of asphalt mixes viz., tensile strength, moisture damage, densification and rutting resistance were compared. The results indicated a statistically significant difference in the optimum asphalt binder content from the two mix design methods. The Marshall method of asphalt mix design is found to yield lower optimal asphalt binder content when compared to the Superpave method of mix design. The moisture susceptibility and construction densification index of asphalt mixes designed using Superpave method were found to be significantly lower than that of the mixes designed by Marshall method. Optimization using a Mixed Integer Linear Program (MILP) indicated that the polymer modified asphalt binder outperforms the requirements of engineering properties when compared to other commercial binders used in the study.     

多碎石沥青混凝土路用性能的研究

研究了掺与未掺木质素纤维的多碎石沥青混凝土的路用性能，其中包括马歇尔稳定度，水稳定性，低温抗裂性，高温稳定度，疲劳耐久性和抗 滑性能，并与密级配沥青混凝土进行了对比，结果表明，多碎石沥青混凝土是一种性能优良的沥青混和料。     

The effects of using lime and styrene–butadiene–styrene on moisture sensitivity resistance of hot mix asphalt

This study focuses on determining the effects of styrene–butadiene–styrene (SBS) and using mineral filler with lime on various properties of hot mix asphalt especially moisture damage resistance. The asphalt cement was modified with 2%, 4% and 6% SBS. The lime treated mixtures containing 2% lime by weight of the total aggregate as filler. The physical and mechanical properties of polymer modified binder and binder–aggregate mixes were evaluated through their fundamental engineering properties such as dynamic shear rheometer (DSR), rotational viscosimeter (RV) for binders, Marshall stability, stiffness modulus, indirect tensile strength and moisture susceptibility for mixes. The retained Marshall stability (RMS) and tensile strength ratio (TSR) values were calculated to determine the resistance of mixtures to moisture damage. To investigate clearly the effective of SBS and lime seven freeze–thaw cycle was applied to specimens at TSR test. The results indicate that application of SBS modified binders and lime as mineral filler one by one improves the stability, stiffness and strength characteristic of hot mix asphalt. According to retained Marshall stability it is concluded that addition of only 2% lime have approximately same effect with addition of 6% SBS. Using lime together within the SBS modified mixes exhibit high accordance and exacerbates the improvement of properties. Specimens containing both 2% lime and 6% SBS, have the highest stiffness modulus which is 2.3 times higher than those of the control mixture and showed the least reduction in tensile strength ratio while maintaining 0.70 tensile strength ratio after seven freeze–thaw cycle.     

胶粉掺量对沥青混合料高温抗变形性能的影响

将废旧橡胶轮胎制备成橡胶粉作为沥青改性剂使用,是目前非常热门的研究方向.该研究探讨了不同掺量的再生胶粉对沥青混合料高温抗变形性能的影响.首先在实验室内通过手工研磨将废旧轮胎加工为大小约为60目的胶粉颗粒;然后将胶粉与基质沥青混合,预先制备成胶粉体积掺量分别为10％、20％、30％和40％的四种胶粉改性沥青;设计沥青混合...     

粗骨架沥青混合料路用性能

通过试验研究,系统分析了Superpave和SMA沥青混合料的路用性能,包括原材料性能,级配分析,混合料马歇尔稳定度,水稳定性,低温抗裂性,高温稳定度,疲劳耐久性和抗滑性能,并与密级配沥青混凝土进行了对比分析。