Abstract
Moisture damage to asphalt pavements continues to be a major concern after decades of research. Two of the most common moisture failure modes in asphalt mixtures are adhesive failures between the aggregate and binder and cohesive failures in the binder or mastic. The challenge in conditioning asphalt mixtures for moisture sensitivity is developing a test method that is capable of evaluating adhesive and cohesive failure properties while remaining repeatable, accurate, and practical. There are three methods for conditioning an asphalt mixture for determining moisture sensitivity: AASHTO T 283, ASTM D4867, and ASTM D7870. T 283 is the most common method for evaluating moisture damage. The conditioning involves saturating, followed by freezing–thawing conditioning of specimens to induce pore pressure. D7870 is the moisture-induced stress test (MIST), which dynamically induces pore pressure into the specimen. In this study, both of these conditioning methods were evaluated with a known moisture-resistant mixture and known moisture-sensitive mixture. The different conditioning methods were evaluated with the tensile strength ratio, change in density, and visual inspection. Results show that the most effective method of conditioning to capture moisture-sensitive mixtures is a combination of T 283 and D7870. T 283 accentuates adhesive failures while D7870 accentuates cohesive failure in the mixtures. The proposed conditioning method uses the MIST unit to effectively identify cohesive and adhesive moisture-sensitive mixtures during mixture design and quality control of asphalt pavements.
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