Development of Precision Statement for AASHTO Test Method T 283 Using Rubberized Hot Mix Asphalt-Gap Graded for Asphalt Pavement

Asphalt concrete mixtures are susceptible to moisture-induced damage, which has been identified as one of the major distresses of the pavement structure. The addition of tire rubber has shown to increase the resistance of the asphalt mixture to cracking and moisture damage. The American Association of State Highway and Transportation Officials (AASHTO) test method T 283 is an established process to evaluate the moisture susceptibility of asphalt mixtures. The high variability of T 283 in predicting moisture susceptibility of dense graded hot mix asphalt (HMA) mixtures led to the development of precision estimates under National Cooperative Highway Research Program (NCHRP) Project 9-26A. The performance of rubberized hot mix asphalt-gap graded (RHMA-G) varies from dense graded HMA because of significant differences in their characteristics. Thus, directly applying the precision estimates of T 283 developed for HMA to RHMA-G may lead to even higher variability. To investigate these discrepancies, the California Department of Transportation developed precision estimates for T 283 using a ½ in. RHMA-G mix through an interlaboratory study program and compared the results to the precision estimates developed in NCHRP Project 9-26A. The tensile strength ratios (TSR) were developed from dry and conditioned (wet) indirect tensile strengths measured in accordance with T 283 on replicate samples conducted by 53 participating laboratories. The precision estimates along with the allowable range for single operator and multi-laboratory of TSR results as well as both dry and wet indirect tensile strengths in RHMA-G mixtures measured per T 283 are presented in this paper.