Evaluation of moderate and high RAP mixtures at laboratory and pavement scales

Abstract

The use of reclaimed asphalt pavement (RAP) to replace the virgin materials in asphalt mixtures can result in significant cost savings and provide environmental benefits. As part of the national efforts to support the increasing use of RAP without adversely affecting the long-term performance of asphalt mixtures, a field evaluation of six asphalt mixtures containing moderate and high RAP contents has been conducted on six test sections at the National Center for Asphalt Technology Pavement Test Track since the third research cycle started in 2006. The objective of this study was to present the latest field and laboratory evaluation results of these six RAP mixtures. The field performance evaluated included rutting, roughness, surface texture and cracking. Sections W4 and W3 were constructed with 20% RAP mixes using PG 67-22 and PG 76-22 base binders, respectively. The four other sections, W5, E5, E6 and E7, were paved with 45% RAP mixtures using four different base binder options, consisting of PG 52-28, PG 67-22, PG 76-22 and PG 76-22 + 1.5% Sasobit. The results of this study show that moderate (20%) and high (45%) RAP contents can be used to produce asphalt mixtures that provide good performance, and a softer base binder can be used to improve the performance of a high RAP mixture. In addition, the creep strain rate determined in the indirect tensile test at 10 °C closely matched the field performance ranking – the mix with a higher creep strain rate exhibited more cracking in the field. The difference between the laboratory and field rank order discussed in this study may be affected by the different laboratory and field specimens and testing conditions, illustrating challenges when one uses smaller scale specimens and/or tests to simulate the performance and results of much larger scale pavement sections.