Moisture, Rutting, and Fatigue-Cracking Susceptibility of Water-Carrying, Wax-Based, and Chemical-Based Warm Mix Asphalt Systems

Abstract

The type of the manufacturing technology as well as the reduced production temperatures of warm mix asphalt (WMA) always raise controversy about the early life and long-term performance of WMA mixtures, more specifically concerning the resistance to stripping, permanent deformation, and fatigue cracking. The present paper is primarily oriented to evaluate such major controversial aspects of WMA moisture, rutting, and fatigue-cracking susceptibility. For this purpose, an experimental campaign and indices were developed to discern the properties among WMA systems in comparison to reference hot mix asphalt (HMA) system. The bonding strength (BS) test was developed to quantify the unconditioned and conditioned failures at the adhesive scale. In addition, the evolutions of the mechanical damage and air voids of asphalt mixtures under the effects of multiple freeze–thaw cycles (FTCs), were evaluated. The rutting susceptibility of mixes was assessed using a developed measure, namely, strain index (SI), which is based on strain/deformation results of the creep-recovery test. Continuous and intermittent fatigue tests were employed to determine fatigue life as well as the healing potential of the mixes. The zeolite-, wax-, and chemical-based WMA technologies provided comparable-to-better BS when compared with the HMA systems. Based on the results of unconditioned and retained tensile strength after multiple FTCs, moisture-induced degradation showed that HMA mixes can withstand more FTCs than WMA mixes. The results of SI indicated that the zeolite WMA produced at low temperature is more susceptible to rutting performance (i.e., lower SI), however the chemical-based mixtures are on par with that of HMA, but wax-based additive is more beneficial to mitigate such distress. The unfavorable influence of reduced production temperature (from 145°C to 120°C) was distinguishable for the rutting results only. The three WMA products produced asphalt mixes at reduced temperatures with better or comparable fatigue life. Using the intermittent fatigue tests, both the hot and warm mixes showed better healing efficiency.