Mechanical properties of asphaltic concrete mixture with crumb rubber and aged binder

A major problem affecting environmental pollution is the unprecedented increase of waste scrap-tires. Furthermore, a rapid economic and industrial growth generates increase in the quantities of solid waste materials includes millions pieces of scrap-tires in the worldwide. The lack of proper controlled use such wastes would lead to be added disposal costs, increase illegal dumping and inadequate storage, and could increase the risk of fires and environmental damages. In this research study, an attempt to inspire a green technology which is more environment-friendly that can provide an economic value is a major consideration in the use of the crumb rubber (CR) as a modifier material in asphaltic mixtures. In asphaltic concrete production technology, there are two methods to introduce waste CR in the roads construction either as aggregates during dry process or as a binder modifier during wet process. The wet process is the most popular method as compared to the dry process. The primary objective of this study was to investigate the effect of adding CR as a modifier material before and after bitumen aging on the ACW 14 mix performance properties using wet process. The research study had three phases. In the first phase, modified bitumen binders were prepared and tested before and after exposure to aging process, and then investigate the CR to resist temperature variations. In the second phase, Marshall Test was conducted on asphalt mixtures containing different bitumen contents to determine the optimum bitumen content (OBC). The OBC was added to design the rubberized ACW 14 mixes. Finally, the performance of rubberized ACW 14 asphalt mixtures containing various CR contents in term of Marshall, indirect tensile strength, stiffness, permeability and moisture susceptibility were investigated and compared with non-reinforced mixtures. The result of binders’ tests and analysis showed that CR can improve the asphalt binder and it is able to decrease the aging degree and reducing the temperature sensitivity. The results also indicated that the Marshall stability, stiffness and indirect tensile of rubberized asphalt samples were obviously higher before and after aging process in comparison with that of unmodified samples. The permeability of rubberized ACW 14 asphalt mixtures were higher; as well as the aged samples had higher permeability values compared with unaged samples due to increase air voids. Further, the results show that the addition of CR into the mixture has a significant effect on the water-induced damages resistance. In this research study, the OBC was found to be 5.2 % by weight of the total mix, while the optimum amount of the added CR (OC CR) was found to be 10 % by weight of the bitumen binder