The Effects of Crumb Rubber and Sasobit on Resistance Parameters of Hot Mix Asphalt

To improve the performance and durability of hot mix asphalt against different kinds of distresses, various additives are used. Among these additives, using crumb rubber has showed to have positive effects on increasing the resistance of ashalt mixtures against fatigue and rutting. Also, the use of Sasobit has been effective on decreasing the temperature of mixture and compaction and therby decreasing the aging during the production stage. The purpose of the present study was to investigate the single effects of rubber powder and Sasobit as well as the combined effects of these two additives on parameters such as Marshal stability in dry and wet states, fatigues at different levels of strain, rutting and resilient modulus. Different mixtures were prepared individually with rubber powder (10, 15 and 20 percent) as well as Sasobit (1, 2 and 3 percent) and then mixtures with optimal amount of each additive resulting from different mixtures wer prepared and underwent relevant tests. Results showed that adding the rubber powder and Sasobit, individually and combined, led to an increase in the resistance parameters. The Marshal ratio in dry state (1 and 10 percent) and in wet state (1 and 15 percent) for sasobit and rubber powder, respectively, reached its maximum level. In the beam fatigue test and rutting, the optimum percentages of sasobit and rubber powder were found to be 2% and 15% and the rutting percentage in 2% and 3% sasobit was similar. Increasing the resilient modulus with different amounts of additives was not significant. The highest impact of these two additives was on the fatigue resistance and rutting parameters. The effect of concurrent use of these two additives on increasing fatigue resistance and rutting was remarkable.