Determine the Impact of Degree of Blending and Quality of Reclaimed Asphalt Pavement on Predicted Pavement Performance using Mechanistic-Empirical Design Guide (MEPDG)

Abstract

Past studies have indicated binder from reclaimed asphalt pavement (RAP) aggregates do not fully blend within the hot mix asphalt (HMA), resulting in a partial degree of blending (DOB). The degree of blending is defined as the percentage of RAP binder that is effectively mobilized within the mix. Most state agencies assume full blending, which is an assumption that may lead to under asphalting or a relatively stiffer mix. However, it is unclear how this will affect the predicted pavement performance. Quality of RAP is yet another parameter that affects performance and DOB. This study focuses on determining the impact of DOB and RAP quality on predicted pavement performance using MEPDG level I analysis of 25% RAP mixes with three RAP sources. Dynamic complex modulus tests were conducted on each RAP source with two conditions: full blending and a calculated “Actual” DOB. MEPDG level I analysis was conducted using typical structures, climate, and traffic conditions for the state of New Jersey. Also rutting and fatigue cracking performance between the two DOBs were compared for each of the RAP sources. The results indicate that DOB has a negligible effect on fatigue and rutting performance for the three RAP sources tested, all of which had actual DOB values greater than 85%. Therefore, with hot mix asphalt consisting of RAP with such high DOB values, the full blending assumption would be cost effective and would not compromise the pavement performance. RAP with a uniform gradation would further reinforce this; however, it does not necessarily correspond to better performance, other RAP properties are at play.