Use of Lime as Antistrip Additive for Mitigating Moisture Susceptibility of Asphalt Mixes Containing Baghouse Fines

摘要

This study investigated the effectiveness of hydrated lime as an antistrip additive for mixes containing excess baghouse fines. Wet process of lime addition was used without marination. One percent lime was added to asphalt mixes containing 5.5% Boone and Enka baghouse fines. Moisture susceptibility of mixes was determined by performing TSR tests on mixes with different proportions of baghouse fines, and with or without lime. TSR test results show that moisture susceptibility was dependant on both the concentration of baghouse fines and whether lime was used as an antistrip additive. One percent lime was found to be sufficient to reduce moisture damage to the point that mixes would be acceptable under the current NCDOT criterion of 85% retained strength. In addition, results of this study indicated that presence of hydrated lime in mixes increased the indirect tensile strength values as measured during TSR test for both unconditioned and moisture conditioned specimens. The mix performance was evaluated using the simple shear test device to determine the shear stiffness, rutting, and fatigue characteristics. In general, the results indicated that addition of lime enhanced the mix performance and reduced moisture susceptibility. The asphalt mix shear stiffness values (G*) were higher, rut depths were lower, and fatigue resistance was higher.