Evaluation of fracture and moisture damage performance of wax modified asphalt mixtures

In this study the fracture and moisture damage characteristics of wax modified asphalt mixtures were evaluated. Two types of commercial waxes (FT-paraffin and Asphaltan B) were added to bitumen of penetration grade 70/100. Using this wax modified and unmodified bitumen; total 48 specimens were produced from two sources of aggregates and two levels of gradation. Bitumen properties were determined by conventional test methods, Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) testing. Thermal Stress Restrained Specimen Test (TSRST) was used to evaluate low temperature cracking resistance and cracking behavior of asphalt mixture was investigated at 0°C using Superpave Indirect Tensile Test (IDT). The influence of wax on the asphalt mixture resistance to cracking and moisture damage performance has been evaluated using Hot Mix Asphalt (HMA) fracture mechanics and Superpave IDT test results. The addition of FT-paraffin and Asphaltan B showed better cracking and moisture damage resistance of the asphalt mixture compared to unmodified mixture, but FT-paraffin showed the largest effect on cracking resistance while Asphaltan B showed highest resistance to moisture damage. In BBR test results, mixtures modified with FT-paraffin showed lower limit m value (LmT) which implies minor negative effect in stress relaxation. However, according to TSRST results, the mixtures with both waxes had nearly same fracture temperature as mixture with unmodified bitumen.