Improving fracture and moisture resistance of cold mix asphalt (CMA) using crumb rubber and cement

Due to environmental and economic advantages, cold mix asphalt (CMA) can be considered as a good alternative to conventional hot mix asphalt (HMA). Nevertheless, it has inferior performance compared to HMA, so that the application of CMA is not recommended in the surface layer of pavements subjected to high traffic volume and/or regions with very cold or hot climate. Considering the high potential of distress occurring in the CMAs, this research is aimed at investigating the effect of crumb rubber (CR) on fracture and moisture damage resistance of the CMAs. Different CR percentages were applied through two different modification methods and, then by means of Semi-Circular Bending (SCB) test, the fracture energy and flexibility index (FI) of modified CMAs were obtained and compared with the unmodified HMA and CMA. The moisture sensitivity of the modified CMAs was also evaluated using modified AASHTO T 283. Moreover, the effects of the addition of cement along with CR were investigated. The results show that simultaneous use of 14% CR and 2% cement in the CMA can considerably improve the fracture and moisture damage resistance so that it has comparable performance to the conventional HMAs.