Estimation of resistance to moisture destruction in asphalt mixtures

Moisture damage in asphalt mixtures refers to loss in strength and durability due to the presence of water. The level and the extent of moisture damage, also called moisture susceptibility, depend on environmental, construction, and pavement design factors; internal structure distribution and the quality and type of materials used in the asphalt mixture. In order to assess the moisture destruction, the current study bears out an analytical approach based on surface energy. Two types of bitumen represent very different chemical extremes (AC-10 and AC-20) and the three aggregates represent a considerable range in mineralogy (limestone, siliceous gravel, and granite) were evaluated during the course of this study. Repeated compressive test was conducted on samples in dry and wet conditions under controlled temperature and moisture destruction was monitored as a change in dynamic modulus with load cycles. Further, mixtures including the two types of bitumen with or without hydrated lime were evaluated to determine quantity improvement of hydrated lime on moisture destruction. The result show that AC-20 have less moisture induced damages compared to AC-10 and dynamic modulus values for mixes with AC-20 were higher than the one with AC-10 for all the aggregate types. Hydrated lime increased the dynamic modulus values and wet/dry ratio stiffness. Addition of lime for river gravel samples showed significant difference between two types of bitumen but no major differences were found in crashed granite.