Evaluation of the Impact of Oxidation and Moisture Conditioning on Indirect Tensile Asphalt Cracking Test Parameters and the Tensile Strength Ratio

Abstract

This study evaluated the effect of laboratory oxidation and testing temperature on asphalt mixtures’ moisture damage. The purpose of this study was to present a modified American Association of State Highway and Transportation Officials (AASHTO) T283 testing procedure that is more sensitive to moisture damage in asphalt mixtures. This study assessed the original test conditioning (OTC), short-term oxidative conditioning (STOC), and long-term oxidative conditioning (LTOC). Three performance grades (PGs)—PG 64-22, PG 76-22, and PG 52-34—and three test temperatures—the ambient laboratory temperature (25°C), asphalt intermediate temperature, and climate intermediate temperature (CIT)—were selected. To better understand the oxidation and moisture conditioning effects, AASHTO T283’s Tensile Strength Ratio (TSR%) was utilized. Furthermore, additional analysis of the load–displacement curve parameters was carried out using the Indirect Tensile Asphalt Cracking Test, where an interaction diagram that included the mixture toughness (G_f), ductile–brittle behavior ratio (l₇₅/m₇₅), and their interactions with CT_index was created. Statistical analysis was conducted using analysis of variance and Tukey’s post-hoc analysis to determine an appropriate oxidation and testing temperature where moisture damage is most sensitive. Results showed that higher oxidation and CIT had the greatest impact on TSR%. Moisture conditioning increased the CT_index and oxidation reduced the CT_index. The increase in CT_index was attributable to an increasing l₇₅/|m₇₅| and decreasing G_f. The CT_index decreased because of reducing l₇₅/|m₇₅| and increasing G_f. The statistical analyses showed that asphalt mixtures are more susceptible to moisture damage at STOC and LTOC than OTC. Overall, the findings highlight the need for an alternative oxidation conditioning and testing at the CIT to more accurately detect moisture damage in asphalt mixtures.