Moisture damage of asphalt mixture and its evaluation under the long-term soaked duration

Abstract

The field cores taken from the asphalt pavement were soaked for long term after vacuum saturation. The indirect tensile strength, the failure stiffness modulus and the tensile strength ratio (TSR) of samples are determined by the indirect tensile test with or without the freeze-thaw cycles. The indirect tensile test and unconfined compressive strength test are devised to measure the unconfined compressive strength and cohesion of specimens immersed in the water for different period. Moreover, the sensitivities of each mechanical index to evaluate the moisture damage of long-term immersed asphalt mixture were compared. The test results indicate that the indirect tensile strength, failure stiffness modulus, TSR, compressive strength and cohesion of asphalt mixtures were all decreased due to the long-term action of water. After immersion for 540 days, the loss rate of unconfined compressive strength was the highest, reaching 62.6%, followed by cohesion, whose loss rate was 50.6%, indicating that under the condition of high temperature 60°C, the longer the saturation lasts, the more obviously the compressive strength and cohesion change, which are all sensitive to moisture damage. Under low temperature conditions, compared with the indirect tensile strength and TSR, the loss rate of failure stiffness modulus is 36.8%, representing its moderate sensibility to moisture damage. At early stage of 6 months, these mechanical indexes declined rapidly, and then gradually became slower. The free water remaining in the samples continuously infiltrated into the interface between asphalt film and aggregates, resulting in a decrease in the adhesion and the contact angle between them as well as a decrease in the cohesion.