Performance Evaluation of Hot Mix Asphalt Using 19.0mm NMAS Superpave Gradations

Abstract

Aggregates are the key construction material used in building industry and largest portion of asphalt concrete. Asphalt pavement is composed of binder and aggregate. In asphalt pavement 94 to 95% is aggregate whereas remaining portion is binder that acts as gluing gent. Therefore, gradation is an influential characteristic of aggregate that affects the performance of HMA mixtures like fatigue cracking and permanent deformation. Superpave mix design procedure was followed in this research and Superpave gradation concept includes control points and restricted zone. In Superpave method, the gradation is not permissible to pass through the restricted zone and it was believed that the gradation that compliance with the restricted zone will produce the mixtures that will easily prone to rutting and not provide good performance. This research focus on the performance of 19.0mm NMAS Superpave gradation that is passing above the restricted zone (ARZ), through the restricted zone (TRZ) and below the restricted zone (BRZ). Superpave volumetric was evaluated for the gradations passing ARZ, TRZ and BRZ and the results drawn from the analysis by using statistical software Minitab-15 shows that the gradation passing TRZ shows lowest VMA value followed by ARZ and then BRZ. Hamburg Wheel Tracker test was conducted to evaluate the consequence of rutting potential of each gradation at 20,000 passes. The results shows that the gradation that is passing below the restricted zone was considered as more rut resistant appears to be more rut susceptible as compare to ARZ and TRZ. The result shows that TRZ has highest resilient modulus followed by ARZ and BRZ. The MR values decrease with increase in load duration and temperature because with increase in load duration the accumulated strains in the specimen increases correspondingly decrease in resilient modulus whereas at higher temperature asphalt becomes viscous and aggregate contribution more significant. Two level factorial design was done on ARZ, TRZ and BRZ and the results shows that load duration and temperature individual as well as two way interaction has significant effect on gradations. The overall performance evaluation as well as volumetric analysis of ARZ, TRZ and BRZ shows that the gradation that passed TRZ not only satisfy the volumetric criteria of Superpave but also performs better followed by the gradation that passed ARZ and BRZ.