Balanced Mix Design Benchmarking of Field-Produced Asphalt Mixtures in Maine, U.S.

Abstract

Performance testing has been recognized by state highway agencies (SHAs) in the U.S. and the asphalt paving industry as an important tool to complement volumetric properties for improving asphalt pavement performance. Thus, Maine Department of Transportation (MaineDOT) initiated a research effort in 2019 to evaluate the cracking and rutting resistance of asphalt mixtures using several performance tests, including the Hamburg wheel-tracking test (HWTT), indirect tensile cracking test (IDEAL-CT), cyclic fatigue test, and stress sweep rutting (SSR) test. These tests were conducted on reheated common plant-produced asphalt mixtures, and results were analyzed to: (1) develop baseline rutting and cracking performance; (2) evaluate the effects of mixture properties on the performance test results; and (3) verify the performance enhancement from the extended use of polymer-modified asphalt binders. Several mixture properties, such as nominal maximum aggregate size (NMAS), binder performance grade (PG), binder content (Pb), and reclaimed asphalt pavement (RAP) %, were found to have statistically significant effects on the mixture rutting and cracking resistance, especially the HWTT and IDEAL-CT results. Based on the proposed criteria for rutting strain index (RSI) and apparent damage capacity (Sapp), the asphalt mixtures tested would provide satisfactory rutting performance under heavy traffic, and satisfactory cracking performance under standard traffic. In addition, based on the IDEAL-CT benchmarking results, mixtures with polymer-modified binder and/or smaller NMAS were found to have higher cracking tolerance index (CTindex) results. The information from the research effort will help MaineDOT to achieve its goal to move beyond sole use of volumetric properties for asphalt mixture design and acceptance with the implementation of balanced mix design (BMD) for improving the field performance of asphalt pavements.