One of the effective parameters in the occurrence of fatigue cracking distress is the asphalt binder properties used, which must be controlled by appropriate asphalt binder or additives. In this study, the effect of using Ultra-High-Molecular-Weight Polyethylene (UHMWPE) was investigated on the fatigue cracking potential of asphalt mixtures. Two types of aggregates, asphalt binder performance grade (PG) 64-16, and UHMWPE additive in two percent of the asphalt binder were used in this study, which were tested at two temperatures and five different stress levels. Marshall mix design and indirect tensile fatigue test (ITFT) were used to determine the optimum content of the asphalt binder and the fatigue life of asphalt mixtures, respectively. The results of this study indicated that the application of polymer additives increased the fatigue life of the asphalt mixtures. The fatigue life of specimens made with granite aggregates was longer than those made with limestone aggregates, and the increased life due to the use of UHMWPE was longer in samples made with granite aggregates. As expected, increasing in temperature and stress levels reduced the fatigue life of the asphalt mixtures. This decrease was much lower in samples made of asphalt binder modified with polymeric materials than in control samples.

There are several experimental methods for improving the moisture strength of asphalt mixtures. Utilization of anti-stripping materials is the most prevalent method. In the present paper, the influence of polymer materials on asphalt binder was investigated using repetitive loading test in wet and dry conditions along with thermodynamic parameters based on the Surface Free Energy components of asphalt binder and aggregates. The results obtained from the present study indicated that using Styrene Butadiene Rubber polymer has improved the asphalt mixtures strength against the moisture damage, especially in the specimens made of granite aggregates. Also, Styrene Butadiene Rubber polymer increased the cohesion free energy and reduced the energy released by the system during the stripping event, which represented a decrease in the tendency for stripping. The stripping percentage index, which is obtained by a combination of the results of the repetitive loading test in wet and dry conditions along with the results of thermodynamic parameters, represented that the specimens made of controlled asphalt binder in the loading cycles under wet conditions had a higher stripping rate. It was also concluded that the modulus loss rate in the control asphalt mixtures was faster than the modified specimens.