Fatigue response of HMA containing modified bitumen with nano-clay and nano-alumina and its relationship with surface free energy parameters

This study investigated the fatigue response of hot mix asphalt (HMA) containing nano-clay and nano-alumina modified bitumen and its relationship with surface free energy (SFE) parameters. Four-point bending fatigue test was performed on the HMA specimens made with limestone and siliceous aggregates and the bitumen modified with 2%, 4% and 6% nano-additives. The SFE parameters of modified bitumens with nano-additives and HMAs were measured by Sessile drop and universal sorption device procedures, respectively. The results showed improvement in the fatigue life of both limestone and siliceous mixtures after modification with nano-particles. The highest fatigue life was obtained for the HMA made with limestone aggregate and 6% nano-alumina. Several fatigue life definitions including the traditional and dissipated energy based criteria were used to predict the fatigue life of modified HMAs. According to SFE measurements, the acidic and basic SFE components of modified bitumen decreased and increased by increasing the nano-additives, respectively. Furthermore, the aggregate–bitumen adhesion energy and adhesion magnitude increased by increasing the nano-additives in both studied aggregate types. The results of statistical analysis confirmed the significance of relationship between the HMA fatigue resistance and SFE parameters.