Evaluation of Moisture Sensitivity and Performance of Lime in Hot-Mix Asphalt: Resilient Modulus, Tensile Strength, and Simple Shear Tests

Abstract

The use of hydrated lime in hot-mix asphalt (HMA) is an accepted practice for many state highway departments. However, there are various techniques of introducing lime into the mixture and several factors that favor one method over another. The goal of this study was to evaluate the mechanical properties of lime-treated HMA mixtures before and after multiple cycles of freeze–thaw moisture conditioning. The mechanical tests measured the resilient modulus, tensile strength, and simple shear. In addition, the three test procedures were compared for evaluating the moisture sensitivity of HMA mixtures. With the addition of lime and after multiple cycles of freeze–thaw moisture conditioning, all mixtures demonstrated an enhanced ability to retain the original measured properties. The four methods of lime treatment—dry lime to moist aggregates, lime slurry to dry aggregates, and either a 48-h marination time or no marination time—were found to be statistically equivalent. The evaluation of moisture sensitivity of an HMA mixture is possible with all three mechanical test procedures. Resilient modulus proved to be the best technique for measuring small reductions in strength. When the loss of strength due to moisture sensitivity exceeded 20%, the measurement of tensile strength provided a better statistical correlation.