Asphalt mixture moisture damage assessment combined with surface energy characterization

Moisture damage in asphalt mixtures can be defined as the loss of strength and stiffness due to the presence of moisture in the mixture causing adhesive failure at the binder-aggregate interface or cohesive failure within the binder and/or binder-filler mastic. This paper presents the experimental assessment of moisture damage on asphalt mixture specimens and describes a fundamental approach using an understanding of the mechanisms that influence the adhesive bond between aggregate and bitumen and the cohesive strength of the binder and/or mastic. Combinations of a dense graded asphalt mixture, comprising two aggregate sources (basic and acidic), three filler types and six bitumen grades and sources, were subjected to an accelerated moisture damage procedure known as the Saturation Ageing Tensile Stiffness (SATS) test. The moisture damage of the asphalt mixtures was determined as the ratio of the stiffness modulus of the moisture conditioned versus unconditioned specimens. The SATS results show that increasing the stiffness of bitumen increases the moisture damage resistance of an asphalt mixture, although this effect is dominated by the greater influence on moisture damage of the aggregate source. The results also show that the use of active filler, such as hydrated lime, significantly improves the moisture damage resistance of an asphalt mixture. Finally, a fundamental approach to moisture damage assessment using surface energy measurements is recommended as a complimentary procedure to the SATS test.