The use of crumb rubber for replacing fine aggregate in cold mixture asphalt

In order to consider the environmental impact, this study investigated the effect of crumb rubber on the mechanical performance of cold mixture asphalt. Crumb rubber was obtained from the process of recycling waste tires, which this waste material becomes a major environmental problem due to the rapid increase in the number of motor vehicles in Indonesia. Cold mixture asphalt is an environmental friendly option on flexible pavement, which reduces energy consumption because it does not need heat during the process as in hot mixture asphalt. In this study, laboratory tests were conducted for Dense Graded Emulsion Mixture Type IV. The first stage in this study was to perform laboratory experiments on compacted mixture to determine the optimum residual bitumen content. In the next stage, a series of tests on crumb rubber mixtures were conducted in the optimum residual bitumen content condition to investigate the effect of crumb rubber as a partial replacement of fine aggregate. Fine aggregate in cold mixture asphalt was replaced with 50% of crumb rubber. Three different sizes of crumb rubber, 20 mesh (0.841 mm), 40 mesh (0.42 mm) and 60 mesh (0.25 mm), were applied in a series of laboratory experiments. Tests were done using Marshall Test equipment to obtain the mechanical performance of cold mixture asphalt. The finding indicated that finer crumb rubber produced higher stability than the larger size of crumb rubber. Even though the use of crumb rubber decreased stability of mixtures, it still met the minimum specified requirement of cold mixture asphalt. The stability of the crumb rubber cold mixtures were also comparable to hot mixture asphalt. Replacement of fine aggregate with crumb rubber on cold mixture asphalt is expected to overcome the environmental problems by reuse the waste materials to preserve the natural aggregates.