Effect of Conditioning Procedures on Moisture Susceptibility of Foamed Cold-Mix Asphalt Mixtures

Abstract

In recent years, cold recycling technologies gained significant interest among road agencies and are used as stabilized base layers because of their economic and environmental benefits. One of the most common technologies for cold recycling is using foamed asphalt as the stabilizing agent. Various road agencies specified different moisture-conditioning procedures to characterize the moisture susceptibility of foamed cold-mix asphalt (FCMA) mixtures. Three commonly used conditioning procedures are AASHTO T 283, Standard Method of Test for Resistance of Compacted Asphalt Mixtures to Moisture-Induced Damage, the moisture-induced stress test, and Asphalt Academy’s technical guideline 2. The moisture-conditioning procedure may also affect the moisture-susceptibility ranking among the various FCMA mixtures. Therefore, it is important to understand the effect of the moisture-conditioning procedure on the moisture susceptibility of FCMA mixtures. The objective of the study was to evaluate the influence of three conditioning procedures on the moisture susceptibility and ranking of FCMA mixtures. The laboratory investigation was conducted on mixtures produced with four different recycled asphalt pavement (RAP) contents of 0 %, 50 %, 75 %, and 100 %. Even though a 0 % RAP FCMA mixture is not practical, this mixture was considered in the study to have FCMA mixtures with a wide range of moisture damage susceptibility results. Moisture damage susceptibility was evaluated using two widely used parameters: tensile strength ratio (TSR) and resilient modulus ratio (MR ratio). The two-way analysis of variance and Tukey’s post-hoc comparison indicated that TSR was not affected by the amount of RAP in the FCMA mixtures. Furthermore, TSR results were not affected by the conditioning procedure. On the other hand, both RAP content and conditioning procedures affected MR ratio results.