Influence of Moisture Damage on Resilient Modulus of Asphalt Concrete

Abstract

Deterioration of asphalt concrete pavement by the action of moisture damage is a major problem facing the serviceability and durability of flexible pavement, it starts with micro cracking of the pavement surface due to load repetitions, and followed by stripping and disintegration of pavement layer. In this investigation, the influence of moisture damage on resilient modulus of asphalt concrete had been assessed under repeated tensile and shear stresses. Asphalt concrete specimens have been prepared at optimum asphalt content, and at an additional 0.5% asphalt above and below the optimum. Specimens were divided into two groups, the first group was subjected to repeat tensile and shear under constant stress for specific load repetitions to initiate micro cracks. The second group was subjected to moisture damage cycle, then it was tested as the first group. It was concluded that Moisture damage causes reduction in resilient modulus by (20, 33, 16.5) % after 50 load repetitions while it decreases by (33, 30, 24) % after 500 load repetitions for (4.4, 4.9, 5.4) % asphalt content respectively when tested by ITS. The resilient modulus decreases (44, 14, 25) % after 50 load repetitions while it decreases by (40, 16.5, 24) % after 500 load repetitions for (4.4, 4.9, 5.4) % asphalt content respectively when tested by PSS after moisture damage. The resilient modulus when tested by (ITS) is 10 folds higher than that when tested by (PSS). Optimum asphalt content exhibit high resistance to moisture damage for ITS and PSS test conditions.