Rutting and moisture resistance evaluation of polyethylene wax–modified asphalt mixtures

One of the methods newly introduced in pavement technology to address environmental concerns and reduce total gas emission is warm mix asphalt (WMA) technology. In this study, polyethylene wax is used to produce WMA mixtures. Although this technology has several positive features, moisture and rutting resistance of WMA mixtures are always questionable. To evaluate moisture and rutting resistance of polyethylene-modified mixtures, indirect tensile strength and dynamic creep tests were used, respectively. Results indicated that polyethylene has positive effect at low compaction temperature on moisture resistance, and also has negative effect on rutting resistance.     

Laboratory evaluation of the effect of bentonite on performance of bitumen and hot mix asphalt mixtures

In this research study, bentonite additive was used to modify original binder (60–70 penetration grade). The experimental program included use of five percentages of bentonite (10%, 15%, 20%, 25%, and 30%) by weight of bitumen. Physical properties of modified and unmodified bitumen were evaluated through penetration grade, softening point, ductility, and temperature susceptibility tests. The performance characteristics of mixtures were determined through indirect tensile strength, resilient modulus, and moisture susceptibility tests. The results demonstrate that addition of bentonite improves Marshall stability, tensile strength, and resilient modulus of mixtures, but led to decrease the resistance to moisture damage.     

The influence of nanoclay on the performance properties and moisture susceptibility of rubberized asphalt mixture

The authors investigated the effect of nanoclay (NC) on the performance properties and moisture susceptibility of rubberized asphalt mixtures. Two percent crumb rubber modifier (CRM) and NC in both combined and separate modes and the effects of each additive on bitumen performance were examined through administering tests of penetration grade, softening point and temperature susceptibility. Also, indirect tensile strength tests in both dry and saturated states were performed to allow for measuring the moisture susceptibility of asphalt mixtures. Moreover, the effect size of both additives on improving the bitumen performance and asphalt mixtures was assessed by running analysis of variance method and sensitivity analysis. The results of the laboratory test and statistical analyses revealed that CRM and NC improved the properties of bitumen and asphalt mixtures. This improvement was associated with the content and type of the additives applied, and also bitumen and asphalt mixtures had the best performance in presence of a combination of CRM and NC.     

岩沥青改性沥青路用性能试验研究

通过车辙试验、冻融劈裂试验及汉堡轮辙试验对两种不同岩沥青改性沥青混合料的路用性能进行试验研究;并与70号普通道路石油沥青混合料进行了汉堡轮辙试验对比。在试验研究的基础上对使用岩沥青改性沥青后沥青混合料的路用性能进行了分析。     

Performance properties of devulcanized waste PET modified asphalt mixtures

The purpose of this research is to evaluate the potential incorporation of the devulcanized polyethylene terephthalate (PET) in enhancing the performance characteristics of modified asphalt mixes. To achieve this aim, seven asphalt mixtures with different percentages of devulcanized waste PET (DWP) (0, 2.5, 5, 7.5, 10, 12.5, and 15 wt% of asphalt binder) were fabricated with wet process. The physical and mechanical properties of unmodified and DWP modified mixtures were investigated using the Marshall stability, indirect tensile strength, and wheel track tests. Based on the test results the presence of PET increases Marshall stability while reduces moisture susceptibility and rutting depth of modified mixtures compared to control mixes. However, superior results obtain for mixtures modified with 7.5–10% of DWP.     

道路沥青温度敏感性研究进展

温度敏感性是道路沥青重要的流变性质之一，综述了道路沥青温度敏感性的研究进展，包括沥青的化学组成与温度敏感性的关系以及温度敏感性评价指标，总结了研究成果，指出了目前存在的问题，并提出将来的研究方向和发展趋势。     

A statistical analysis on the mechanical properties of nanocomposite modified asphalt mixtures

This study aimed to characterize the rate of change that takes place in the mechanical properties of polymer-nanocomposite asphalt (PNMA) mixtures due to altering asphalt binder grade and styrene-butadiene-styrene (SBS) type. Laboratory testing program included Marshall stability, resilient modulus, and wheel-tracking tests. Test results were compared and analyzed statistically by means of two-way analysis of variance and Tukey test. Variance analysis indicated the significant effect of both binder type and SBS grade on mechanical properties of asphalt mixtures. Interaction between binder type and SBS grade is also meaningful in all the experiments. The results also show that the binder type is the primary affecting factor, followed by the SBS grade.     

The rheological behavior of bitumen and moisture susceptibility modified with SBS and nanoclay

The effect of styrene–butadiene–styrene (SBS) and nanoclay additive on performance of pure bitumen and stone matrix asphalt (SMA) mixture was investigated. Different samples with various percentages of nanoclay (2%, 3%, 4%, and 5%) and SBS (0% and 5%) by weight of bitumen were prepared, and the rheological and chemical behavior of bitumen (rotational viscosity, dynamic shear rheometer, SEM, and FTIR), the indirect tensile strength and moisture susceptibility of different mixtures were evaluated. Based on the results, using nanoclay and SBS polymer can improve the rheological behavior of base binder and the resistance of SMA mixtures against moisture damage.     

Warm asphalt mixtures produced with addition of CCBit

There is a growing concern with the environmental damage caused by the various types of industrial activities. Because of that, research in paving has sought alternatives to reduce fuel consumption and emissions of greenhouse gases generated by those. The warm mixtures have received increasing attention because they are capable of decreasing the mixture and compaction temperatures of asphalt mixtures. The objective of this study was to evaluate the effect of the incorporation of CCBit from the mechanical characterization of asphalt mixtures. From the results, it was found that the incorporation of CCBit has the advantage of reducing mixing and compaction temperatures without harming their mechanical behavior.     

Characterization of rutting resistance of EBS-modified asphalt mixtures

Driven by Kyoto protocol to reduce the gas emission, warm mix asphalt (WMA) as an alternative of hot mix asphalt has gained huge interest among researchers. Despite many advantages, rutting resistance of WMAs is always questionable. In this study, ethylene bis(stearamide) (EBS) was used as a wax-based additive to produce WMAs. Samples were produced at three different compaction temperatures. To evaluate rutting resistance of mixtures, all cylindrical specimens were tested by dynamic creep and dynamic modulus tests at various compaction temperatures. Results indicate that rutting resistance of EBS-modified samples are remarkable, especially when compaction temperature is low.     

沥青针入度温敏性表征法的改进试验

为研究针入度温度的关系，扩大针入度测定的温度范围，利用总质量50g和100g加长的针入度针实测沥青在使用温度区间的针入度变化。按不同配重、不同温度和不同贯入时间，比较了四种沥青对温度和贯入时间的反应，利用针入度对数值和温度的关系表征沥青在该温度区间的温度敏感性：。结论认为：应用总质量50g的加长的针入度针可以使测定温度区间和针入度检测范围扩大；而直接用1gp表达式里面的A值，以比较斜率的方式表征沥青对温度变化的敏感性，比较接近实际情况；在实测温度区间内，弹性体改性沥青的温度敏感性较纯沥青为好。     

柔性基层沥青混合料配合比设计研究

针对柔性基层这一特殊层位进行了系统的配合比设计研究,结合实际给出了5种沥青混合料的级配范围,通过马歇尔试验,按照现行规范的流程,分别确定出各级配的最佳油石比。并依据柔性基层抗车辙和抗水损坏能力的需要,对其进行了相应的性能验证试验,结果表明各级配沥青混合料均能很好满足相关规范的要求。     

Effects of nanoclay on hot mix asphalt performance

The purpose of this study was to evaluate of nanoclay effects as an additive on performance of asphalt mixtures. Two types of montmorillonite nanoclay, namely CA and CB, were used at concentrations of 2%, 4%, and 6%. Marshall, indirect tensile strength, resilient modulus, and dynamic creep tests were performed to investigate the effect of additives on moisture susceptibility, structural response, and rutting resistance. The results showed improvement of the asphalt mixture performance by adding nanoclay with respect to all tests. According to the results, samples containing nanoclay CA have better performance in comparison with the samples containing CB.     

Evaluation of rutting resistance of asphalt binders and asphalt mixtures modified with polyphosphoric acid

In this research, a polyphosphoric acid (PPA) additive was used to modify a performance graded binder (PG 58-22). Experimental program included use of three PPA contents (0.5%, 1%, and 1.5%) by weight of bitumen and use of antistripping limestone aggregates. High-temperature rheological properties of asphalt binders were evaluated through the frequency sweep test. Complex modulus test was also used to evaluate rutting characteristics of asphalt mixtures. Results showed that PPA significantly improved rutting resistance of both unmodified asphalt binder and unmodified asphalt mixture, especially for the asphalt binder.     

基于路用性能的沥青混合料高温稳定性评价指标研究

对沥青混合料的动稳定度（标准条件以及非标准条件）、蠕变劲度、高温抗压强度等指标进行了室内试验,结合对应实体工程车辙深度的跟踪观测结果,对各项室内高温指标与现场车辙深度之间的相关性进行了分析。研究表明：0.7 MPa条件下的动稳定度及相对变形、蠕变劲度、抗压强度等指标之间有较好的一致性,与实体工程的高温稳定性之间无明显相关性;1.05 MPa、50%保证率温度条件下的动稳定度,与实体工程的实测车辙深度具有良好的相关性。     

加工工艺条件对胶粉改性沥青性质的影响

用废汽车轮胎粉生产改性沥青不但可以提高沥青的使用性能。还可以解决其"黑色污染"问题。以欢喜岭沥青为原料,采用湿法生产胶粉改性沥青过程中,剪切温度、剪切速率、剪切时间和胶粉加入量等都会影响胶粉改性沥青的性质。     

Evaluating the effect of different asphalt mixtures on hydroplaning using a new lab-scale apparatus

Skid resistance of asphalt pavements is one of the most important road criteria for users' safety. In a rainy condition the skid resistance is largely compromised and when the road surface is flooded, vehicles can experience hydroplaning at a certain critical speed. Tires under hydroplaning conditions become separated from the pavement surface and the ability of tires to increase braking force or cornering traction for stopping or controlling vehicle motion is almost entirely lost. In this study, a new lab-scale apparatus was designed and manufactured, which can stimulate hydroplaning and evaluate the impact of different asphalt mixtures on this phenomenon. To evaluate various mixes, three types of asphalt mixtures with different grading are made and mean texture depth and British pendulum number are measured by six repetitions. By using this apparatus in dry and wet conditions of pavement surface, five different frequencies are tested in terms of hydroplaning. The results show that there is 33% increase in hydroplaning occurrence speed by increasing mean texture depth by 0.5 mm.     

沥青混合料疲劳性能研究及寿命预估的新方法

裂缝是沥青路面破坏的主要形式。裂缝主要分为疲劳裂缝、反射裂缝和温缩裂缝。当沥青路面重复地经受某一荷载应力时就会发生疲劳裂缝。为了减少沥青路面产生疲劳裂缝，必须了解沥青混合料的疲劳产生机理，并对疲劳寿命进行研究。通过概述沥青混合料的疲劳机理，并对最常见AC-20I型沥青混合料进行疲劳试验，回归出基于应变模型疲劳寿命的公式，同时为了提高疲劳寿命方程的实用性，采用SPSS多元回归模型预估疲劳寿命，最后建立室内试验和实际路面的疲劳寿命换算系数。     

Investigation of fatigue life of asphalt mixtures based on the initial dissipated energy approach

The present research study addresses the fatigue life of different asphalt mixtures by means of 4PBF test. To this end, the fatigue behavior of unmodified asphalt mixtures and modified mixtures with styrene-butadiene-styrene polymer and crumb rubber as modifier were investigated in low and medium strain levels. Results showed that there is an excellent correlation between the fatigue lives of different asphalt mixtures in terms of the dissipated energy approach. It can be observed from result that the amount of initial dissipated energy at the 50th loading cycle predicted the fatigue life of asphalt mixtures without performing millions of loading cycles. Furthermore, the initial dissipated approach provides more reliable results from fatigue life of asphalt mixtures in comparison to the traditional fatigue tests.     

微波辐射对稠油化学组成的影响

微波开采技术可通过电磁波向储层释放物理能量,实现从油藏内部和表面同时进行的"体加热"。针对辽河、胜利、吐哈3个油田的普通稠油特性,开展了实验室微波辐射研究,并对辐射前后稠油化学组成进行了定性和定量对比分析。实验结果表明,微波辐射可引发稠油一系列化学反应,主要方向是从较大分子碎裂为较小分子。杂原子化合物易于发生微波化学反应,导致各非烃组分含量的明显变化和分子级分布模式的改变。主要是从分子质量较高的非烃分子裂解出分子质量较小的高极性非烃分子,并从非烃生成烃类化合物。微波辐射也可能会使大芳烃分子发生侧链断裂,但对小分子烃类(饱和烃和芳烃)化合物的分子分布模式无明显影响。