Evaluation of a Performance-Based Approach to Design Asphalt-Treated Base Mixtures

Abstract

This paper presents the results of a comprehensive laboratory testing program that was conducted to develop a performance-based approach to design asphalt-treated base-course mixtures. Eight asphalt-treated base-course mixtures with different aggregate types were considered and evaluated in this study. The considered aggregates included four limestones, sandstone, granite, novaculite, and rhyolite. The laboratory testing program was conducted in two phases. The first phase, Phase I, was a screening phase that evaluated the physical and strength properties of the aggregates used. Furthermore, this phase examined the high-temperature and intermediate-temperature properties of asphalt-treated mixtures based on the results of the load-wheel tracking and indirect tensile strength tests, respectively. In Phase II, permeability and a suite of mechanistic tests were performed to further examine the behavior of the asphalt-treated mixtures that passed the Phase-I screening evaluation. The mechanistic tests performed in Phase II included dynamic modulus, flow number, semicircular bend, and dissipated creep strain energy tests. The results of the first phase showed that asphalt-treated base-course mixtures with porous limestone aggregates did not pass the screening criterion at intermediate or high temperatures. Among all asphalt-treated mixtures evaluated in Phase II, the mixture containing the novaculite aggregate exhibited the least rutting and fracture resistance. In addition, asphalt-treated base-course mixtures containing limestone aggregates showed the best laboratory performance and met the minimum criteria in all conducted tests for well-performing conventional base-course hot-mix asphalt (HMA) mixtures. The results of the study also indicated that the parameters characterizing the coarse and fine portions of aggregate gradation significantly affect the critical strain energy release rate of asphalt-treated mixtures. In addition, the results of the dissipated creep strain energy test exhibited good correlations with the aggregates’ absorption and the mixtures’ film thickness. Finally, the cost of asphalt-treated base-course mixtures evaluated in this study was approximately $7.20 per ton lower than that of conventional HMA base-course mixtures. This corresponded to about a 16% reduction in price.