Evaluating the Impact of Reclaimed Asphalt Pavement on the Mechanical Performance of Hot Mix Asphalt

Abstract

This study  assessed the impact of integrating reclaimed asphalt pavement (RAP) and its moisture condition on the mechanical performance of hot mix asphalt (HMA). Using the standard Marshall method,  mixtures with 0%, 10%, 20%, 30%, 40%, and 50% RAP were prepared, and for each mix, the optimum asphalt content (OAC)  was found. Two moisture states of RAP (oven-dried and saturated surface-dried) were examined to assess its sensitivity to residual moisture. The results showed that adding more RAP to the mix lowered the OAC from 5.22% (control) to 4.87% (50% RAP), reflecting the influence of the aged binder. When the RAP levels were higher, the Marshall stability was enhanced, and the flow decreased, which meant that the mixture was stiffer. However, at high RAP levels, stiffness often exceeded the allowed limits. RAP mixtures showed increasing tensile strength values up to 20% RAP, but   decreased at higher levels. Residual moisture in RAP greatly affected mechanical performance. Specimens prepared with saturated RAP were less stable, had higher flow, and had a much lower indirect tensile strength than dry specimens, which was exacerbated after 20% RAP. Up to 20% RAP can be used without lowering the quality of the mixture, as shown by the fact that RAP levels and moisture conditions, as well as volumetric (V_a, VMA, VFA) and mechanical parameters, meet SCRB R/9 2007 and ASTM performance standards. Suggestions include managing RAP moisture by properly stacking it, either by covering it or using conical-shaped stockpiles.