Residual Moisture As A Source Of Distress In Asphaltic Concrete Pavement

One of the primary concern during design and construction of asphalt pavement is moisture damage which occur due to the separation and removal of asphalt binder from the aggregate surface in the presence of water, thus, leading to stripping and potentially causing premature failure. Sometimes moisture might not be due to the post laid environmental conditions, but due to inability of the drying process to produce moisture free aggregates at the mixing plant, thus residual moisture. The maximum allowable residual moisture is debatable, in USA specifications on allowable residual moisture content vary from state to state ranging from 0.5 to 2%. The aim of this research is to evaluate the effect of residual moisture in asphalt concrete mix. The aim of this study was achieved by performing moisture susceptibility test on asphalt concrete samples produced with poorly dried aggregates containing 0.5%, 1.0%, 1.5% and 2.0% residual moisture, and asphalt mixture produced with dried aggregates. The result was analyzed by means of response surface methodology (RSM) using Design Expert 7.0 software and validated using analysis of variance (ANOVA). The results obtained show that, residual moisture endangers the strength, durability and performance of asphalt concrete mixes by increasing stripping potentials. The susceptibility increases with the increase in residual moisture. The findings of this research indicated that even minimum residual moisture has effect on the strength characteristics of asphalt concrete mixture; therefore it needs to be eliminated.