Evaluation of moisture susceptibility of porous asphalt concrete using water submersion fatigue tests

Porous asphalt concrete due to its open structure is exposed to water and therefore susceptible to water damage. Effect of water, temperature and frequency on mechanical properties of porous asphalt concrete was investigated. An innovative test method developed in Switzerland is used to mechanically test 150 mm diameter cylindrical cores from eight materials in dry state and while being submerged under water. Although the conventional indirect tensile strength ratio delivers useful data about the water sensitivity of porous asphalt specimen, the coaxial shear test provides vital information about the development of fatigue damage in the material. Application of coaxial shear test (CAST) for a twin lay porous asphalt as well as conventional porous asphalt shows a reduction in complex modulus due to fatigue loading after each thermal cycle and due to detrimental effects of water submersion. Moisture susceptibility results using CAST reflected the field inspections of surface degradation. In addition, investigation of the microstructure has given insight into the mechanical behavior of selected materials.