Investigation of damage and deterioration hazard in asphalt mixtures due to moisture

Damage to hot-mix asphalt due to moisture is one cause of distress in pavements. Prediction and prevention of this phenomenon is an important research activity in pavement engineering. This study used an analytical approach based on surface energy to interpret results from dynamic compressive loading tests. Dynamic modulus tests applied a repeated axial cyclic load with fixed magnitude and cycle duration to test specimens in dry and saturated states. Two types of bitumen binder, different aggregate types and gradations were evaluated in this research. The aggregates used represented a considerable range in mineralogy (granite, limestone and siliceous gravel) and the bitumens had very different chemical properties. The change in dynamic modulus with load cycles was investigated as moisture damage occurred. Analysis of data considered mixture properties, such as bond energy, in order to assess the influence of moisture. In this research, mixtures with or without hydrated lime, made from the two types of bitumen but only one aggregate, were also evaluated. This study showed that the hydrated lime can substantially improve the resistance of the mixtures to moisture damage. The results also indicated that samples with AC-20 bitumen or crushed granite had less moisture damage compared to other mixtures.