Evaluating the Effect of SBR Polymer Modified Bitumen on the Moisture Susceptibility of HMA

Using anti-striping additives is the most optimal method to improve the strength of asphalt mix against moisture. In this survey, it is tried to review the effect of using polymeric materials as bitumen modifiers on the reduction of moisture damage of hot asphalt mix. To investigate the effect of polymeric materials, repetitive loading test in dry and wet condition together with thermodynamic parameters have been used. The results showed that using Styrene-Butadiene Rubber (SBR) have led to improve the ratio of wet to dry module of asphalt mixes, showing their strength against moisture damage. Moreover, SBR have increased the conjunction free energy and have decreased the released energy of system in striping event and this indicates drop in system’s tendency to striping. Moisture susceptibility index which is the surface percent of aggregates exposed to moisture have been obtained according to the measuring the components of surface free energy of bitumen and aggregate and asphalt mix module in loading cycles. The results of this index showed similar results to the ratio of dry module to wet module. Obtained results represents that SBR has led to considerable decrease in striping percentage in samples of controlled asphalt mixes.