Investigating the Rutting and Moisture Susceptibility of Asphalt Mixtures Using Accelerated Pavement Testing and Establishing Performance Based Pay Factors

Abstract

The objective of this research is to assemble and instrument an accelerated pavement tester (APT) that can reliably be used in asphalt mixtures evaluation. Several applications were conducted on the APT. The APT used in this study was designed, assembled, and instrumented to allow simultaneous accelerated testing of different asphalt mixtures, in both dry and wet conditions, at different load amplitudes and temperatures. The first two applications included asphalt mixtures with deviations in their binder content and air voids based on the standard specifications of transportation agencies and department of transportation for different states. Then, pay factors that are based on performance metrics were established according to the relative performance of each tested mixture. The purpose of the third application was to investigate the rutting potential and moisture susceptibility of different asphalt mixtures subjected to various loading conditions using an APT. The experimental plan was divided into two stages. Stage one included testing six different asphalt mixtures under dry conditions. This stage aimed at assessing the effect of recycled concrete aggregates (RCA) as a percentage replacement of the coarse aggregates, RCA as a mineral filler, and hydrated lime filler, while incorporating unmodified as well as SBS-modified binders. The second stage included testing the same asphalt mixture variations but under wet conditions. During testing, the rut depth at the center of each sample was recorded at regular intervals to construct the permanent deformation curves as a function of the number of load cycles. The established performance-based pay factors were reasonable and comparable with those set under penalties by DOTs. However, there were some limitations that are discussed in the study. Moreover, the results of the third application indicated that including hydrated lime filler into mixtures with RCA aggregates could lessen the rutting potential exacerbated by moisture damage. However, excessive bleeding was observed in mixes incorporating both SBS-modified binder and hydrated lime. In addition, asphalt mixtures incorporating RCA aggregates exhibited higher moisture damage, while those with RCA mineral filler had similar performance to mixtures with limestone filler in terms of rutting and moisture susceptibility.