EVALUATION OF NANOSILICA MODIFIED STONE MASTIC ASPHALT

Stone mastic asphalt is a gap graded asphalt mixture used in heavily trafficked highways due to its high resistance to rutting. However, stone mastic asphalt has some shortcomings such as more susceptible to moisture damage compared to other types hot mix asphalt and excessive and unstable binder content which leads to rutting when heavy loads are applied at high ambient temperatures. One of the ways to improve the performance of stone mastic asphalt is to modify the bitumen using nanosilica, which has strong absorption, large surface area and excellent stability. The objective of this study is to investigate the use of nanosilica as a bitumen modifier to improve the moisture susceptibility, stiffness and rutting resistance of stone mastic asphalt mixtures. Bitumen PEN 60/70 was modified with nanosilica at 2% by weight of bitumen. The performance of the stone mastic asphalt specimens were then evaluated in terms of its moisture susceptibility, stiffness and rutting resistance. The results obtained from the testing showed that the addition of nanosilica increased the resilient modulus value and reduced the rutting depth of stone mastic asphalt mixes, while achieving the required moisture resistance. It can be concluded that the addition of nanosilica in the bitumen improved the performance of stone mastic asphalt mixtures.