Evaluation of Moisture Damage and Stripping of Asphalt Concrete Prepared With New Additives of Polymer Modified Bitumen

The moisture induced damage and stripping are two of common reasons of premature failure of flexible pavement. The current research involved an extensive experimental investigation on two types of polymers (Novolac and PVA) as modifiers in order to produce Polymer Modified Bitumen (PMB). Different ratios of both additives were investigated for rheological properties of binder and mechanical properties of Hot Mix Asphalt (HMA). The rheological properties of PMB were evaluated by penetration, softening point, ductility and thin film oven tests. The mechanical properties of HMA were assessed by Marshall Stability test, Retained Marshall Stability test, indirect tensile strength test, Tensile Strength Ratio (TSR), and striping test. The results of tests showed that the Novolac modifier improves the cohesion properties of binder and the adhesion of binder to aggregate. The PVA modifier mainly improves the adhesion of binder to aggregate with less degree of that of using Novolac. Both modifiers significantly improve moisture sensitivity and decrease the stripping of HMA. Also, the results showed that the addition of 2% of Novolac to binder to produce PMB represents the optimum option. The HMA with PMB Novolac 2% improves the Marshall Stability, Retained Marshall Stability, and TSR by 45%, 14% and 44% respectively. The very small amount of these additives compared with mix components and their reasonable price make them a superior and practical solution for premature failure of flexible pavement