This paper presents the results of a laboratory-based experimental investigation on the properties of asphalt binder and hot-mix asphalt (HMA) mixes modified by locally available crumb rubber, which was used as a partial replacement of asphalt by weight. In this study, fine crumb rubber with a particle size in the range of 0.3–0.6 mm, obtained from scrap tires, was added to the asphalt binder through the wet process. Crumb rubber contents of 5%, 10%, 15%, and 19% by weight of asphalt were added to the virgin binder in order to prepare the modified asphalt binder samples, while the unmodified asphalt binder was used as the control sample. The crumb rubber modified binder samples were examined for measuring viscosity indirectly using the penetration test, and temperature resistance using the softening point test. Later, both the modified and unmodified asphalt binders were used to produce HMA mixes. Two categories of HMA mix commonly used in Malaysia—namely, AC 14 (dense-graded) and SMA 14 (gap-graded)—were produced using the modified asphalt binders containing 5%, 10%, 15%, and 19% crumb rubber. Two AC 14 and SMA 14 control mixes were also produced, incorporating the unmodified asphalt binder (0% crumb rubber). All of the AC 14 and SMA 14 asphalt mixes were examined in order to determine their volumetric properties, such as bulk density, voids in total mix (VTM), voids in mineral aggregate (VMA), and voids filled with asphalt (VFA). In addition, the Marshall stability, Marshall flow, and stiffness of all of the AC 14 and SMA 14 mixes were determined. Test results indicated that the modified asphalt binders possessed higher viscosity and temperature resistance than the unmodified asphalt binder. The viscosity and temperature resistance of the asphalt binders increased with the increase in their crumb rubber content. The increased crumb rubber content also led to improvements in the volumetric properties (bulk density, VTM, VMA, and VFA) of the AC 14 and SMA 14 mixes. In addition, the performance characteristics of the AC 14 and SMA 14 mixes—such as Marshall stability, Marshall flow, and stiffness—increased with the increase in crumb rubber content. However, the AC 14 mixes performed much better than the SMA 14 mixes. The overall research findings suggest that crumb rubber can be used to produce durable and sustainable HMA mixes, with manifold environmental benefits, for use in flexible pavements carrying the heavy traffic load of highways.

中文翻译：

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包括从废旧轮胎中获得的本地碎橡胶在内的热拌沥青混合料的材料特性和环境效益

本文介绍了基于实验室的实验研究的结果，该实验研究了由当地可得的碎屑橡胶改性的沥青粘合剂和热混合沥青（HMA）混合物的性能，该橡胶被用作部分沥青的重量替代。在这项研究中，通过湿法向废料中添加了由废轮胎获得的粒径在0.3–0.6 mm范围内的细碎橡胶。为了制备改性沥青粘合剂样品，将5重量％，10重量％，15重量％和19重量％的沥青橡胶含量添加到原始粘合剂中，而未改性沥青粘合剂用作对照样品。使用渗透测试间接检查了碎胶改性的粘合剂样品的粘度，并使用软化点测试间接测试了耐热性。之后，改性沥青和未改性沥青粘合剂均用于生产HMA混合物。马来西亚常用的两类HMA混合物即AC 14（致密等级）和SMA 14（间隙等级）是使用含有5％，10％，15％和19％碎胶的改性沥青粘合剂生产的。还生产了两种AC 14和SMA 14对照混合物，其中掺入了未改性的沥青粘合剂（0％碎屑橡胶）。检查了所有AC 14和SMA 14沥青混合料，以确定其体积特性，例如堆积密度，总混合料中的空隙（VTM），矿物骨料中的空隙（VMA）和填充沥青的空隙（VFA）。此外，确定了所有AC 14和SMA 14混合物的马歇尔稳定性，马歇尔流量和刚度。试验结果表明，改性沥青结合料比未改性沥青结合料具有更高的粘度和耐温性。沥青粘合剂的粘度和耐热性随其碎胶含量的增加而增加。废胶含量的增加还导致AC 14和SMA 14混合物的体积特性（体积密度，VTM，VMA和VFA）得到改善。此外，AC 14和SMA 14混合物的性能特征（例如马歇尔稳定性，马歇尔流动性和刚度）随碎橡胶含量的增加而增加。但是，AC 14混合物的性能要比SMA 14混合物好得多。总体研究结果表明，碎胶可用于生产耐用且可持续的HMA混合物，具有多种环境效益，