Material optimization and optimum asphalt content design of asphalt mixture in salty and humid environment

Abstract To improve the water stability of asphalt mixture in coastal areas, the optimization of asphalt anti-stripping agent and the design of optimum asphalt content were studied according to the characteristic of salty and humid environment. Firstly, the improved boiling water test was put forward to determine the type and dosage of anti-stripping agent suitable for salty and humid environment preliminarily. Secondly, the improvement effect of anti-stripping agent on water stability of asphalt mixture was evaluated. The type and optimum dosage range of asphalt anti-stripping agent were eventually determined. Finally, the design method of optimum asphalt content based on indirect tensile strength ( ITS ) for asphalt mixture in salty and humid environment was proposed. The results show that the anti-stripping agent of PA-1 (P), HT-09 (H), AMR (A) and TJ-066 (T) all improve the adhesion between asphalt and aggregate in salty and humid environment, but the performance of anti-stripping agent H declines significantly after aging. The anti-stripping agent A is recommended to improve the water stability of asphalt mixture in salty and humid environment. The optimum dosage range of anti-stripping agent A is 0.5–0.6% by weight of asphalt. The temperature of 40 °C and loading rate of 5 mm/min are proposed as appropriate condition for indirect tensile test. Replacing the stability by ITS and combining with volume indexes to determine the optimum asphalt content could ensure good water stability of asphalt mixture in salty and humid environment.