Reclaimed Asphalt Pavement Limits to Meet Surface Frictional Requirements

Abstract

Reclaimed asphalt pavement (RAP) is widely used to construct new asphalt pavement layers, but its use is often limited in surface courses because of concerns about frictional performance, especially in areas where polish-resistant aggregates are scarce or not available. The goal of the research reported in this paper was to determine the maximum amount of RAP that can be blended with high-friction aggregates and used in surface mixes without significantly impacting frictional properties. The properties of RAP from six different sources were evaluated to determine typical RAP characteristics and used to fabricate a mixture simulating a worst-case scenario RAP with a low-friction aggregate. That RAP mixture was used to evaluate the frictional characteristics of two types of hot-mix asphalts with various amounts and types of high-friction aggregates. Specimens were subjected to laboratory polishing to simulate the effects of traffic. Results suggest that the threshold level of RAP in surface mixes that will not have detrimental effect on their frictional properties was about 30%, even when the RAP contained a highly polishable aggregate.