Improving moisture and fracture resistance of warm mix asphalt containing RAP and nanoclay additive

Abstract

Using warm mix asphalt (WMA) and reclaimed asphalt pavement (RAP) has both significant environmental and financial benefits for countries; however, fracture resistance of RAP in subzero temperatures and moisture susceptibility of WMA has been a setback for utilizing these technologies broadly in the field. Since the fracture behavior of WMA and RAP has not been studied simultaneously, this study undertakes to assess the performance of WMA mixtures incorporating various content of RAP materials with the addition of nano clay as additive. In order to meet this objective, fracture toughness of semi-circular bend (SCB) specimens made by different RAP ratio (0, 20, 30 and 40%) and nano clay content (0 and 3%) was studied in two subzero temperatures (−10 and −20 °C) under pure mode I, pure mode II, and two distinct mixed-modes (I/II). Moreover, indirect tensile strength (ITS) and AASHTO T283 tests were conducted to assess the influence of RAP and nano clay on moisture damage of WMA. The results show that the use of both RAP and nano clay has beneficial impacts on WMA mixtures in terms of fracture and moisture resistance. Moreover, the fracture resistance of samples rose with decreasing temperatures, and WMA mixtures are more prone to crack at mode mixities. Overall, the simultaneous use of WMA, RAP, and nano clay seems as an environmentally-friendly mixture that promises a better efficiency compared to conventional WMA.