Effect of MIST Conditioning on Moisture-Induced Damage of RAP Mixes Using Elastic Moduli and Stress–Strain Behavior

Moisture-induced damage of asphalt pavements constitutes a primary distress. To quantify the extent of moisture-induced damage efficiently, a moisture-induced stress tester (MIST) was developed. This study adopts varying stress cycles of MIST to condition the asphalt mixes without and with reclaimed asphalt pavement (RAP) to ascertain their moisture-induced damage resistivity. Hence, the control mix (0% RAP) and mixes containing 10%, 20%, 30%, and 40% RAP by weight were prepared and conditioned using 0, 1,000, 2,000, 3,500, 5,000, and 10,000 stress cycles of MIST. Thereafter, an indirect tensile (IDT) strength test was conducted on the prepared mixes. Using analytical approaches, the biaxial state of stress was defined to compute the static ($E_{S,H}$) and average modulus ($E_{S,A}$). Increasing stress cycles of MIST decreased the stiffness of control and RAP mixes. The compressive stress–strain curve (SSC) was plotted and utilized to compute the linearity and toughness index (TI) of control and RAP mixes. Increasing stress cycles of MIST were observed to increase the ductility of control and RAP mixes, whereas prepeak linearity was observed to reduce it. The TI increased with the increase in stress cycles of MIST. New moisture damage ratios (MDRs) were computed by utilizing $E_{S,H}$ and $E_{S,A}$ and compared with the commonly adopted tensile strength ratio (TSR). Based on such MDRs, it was concluded that RAP improves the moisture-induced damage resistivity of asphalt mixes. Statistical analysis indicated that both $E_{S,H}$ and $E_{S,A}$ have the potential to be good indicators of moisture-induced damage of control and RAP mixes.