The influence of aggregate, filler and bitumen on asphalt mixture moisture damage

Moisture damage in an asphalt mixture can be defined as the loss of strength, stiffness and durability due to the presence of moisture leading to adhesive failure at the binder–aggregate interface and/or cohesive failure within the binder or binder–filler mastic. Various test methods exist to identify the susceptibility of asphalt mixtures to moisture damage, such as the AASHTO T283 procedure. This paper describes a new combined ageing/moisture damage laboratory test known as the Saturation Ageing Tensile Stiffness (SATS) test that has been successfully used to quantify the moisture damage of a range of UK asphalt mixtures. The test consists of initial saturation prior to placing compacted asphalt mixture cylindrical specimens in a moist, high temperature and pressure environment for an extended period of time. The stiffness modulus measured after the test divided by the stiffness modulus measured before the test (retained stiffness modulus), and the specimen saturation after the test (retained saturation), are used as an indication of the sensitivity of the compacted mixture to moisture damage. In this paper, the sensitivity of the SATS test to different aggregates, fillers, binders and volumetric proportions as well as mixture types has been assessed. The results show that the SATS test is able to discriminate between different asphalt mixture combinations in terms of their moisture damage resistance. Compared to AASHTO T283, the SATS test was found to be a more aggressive conditioning protocol, although both tests ranked mixtures in a similar order with respect to moisture damage.