Effect of Water Conditioning for Extended Periods on the Properties of Asphalt Binders

Selecting materials with a low susceptibility to moisture damage (i.e., stripping) is critical to guarantee the performance of asphalt pavements. Stripping in the asphalt mix can accelerate damage and consequently reduce pavement life. Most current research on moisture damage considers the effect of water on the mastic, the aggregate, and the adhesive bond between the aggregate and the binder. However, limited research has been conducted to determine the effect of extended water exposure on the properties of asphalt binders. This study investigated the influence of extensive water exposure on the stripping potential of asphalt binders by measuring the rheological properties, bond strength, and wettability of a Colombian binder before and after immersion. Thin films (2-mm height) of asphalt were immersed in water for 3, 6, and 9 months, and comparisons were made between the experimental results of unconditioned and conditioned binders. Master curves for complex modulus and phase angle were obtained by using a frequency sweep test in a dynamic shear rheometer. The bond strength between the binder and aggregates was measured with the recently developed binder bond strength test. The wettability potential of the conditioned and unconditioned binder was estimated by using the sessile drop method, and dynamic modulus testing of mixes prepared with the unconditioned and conditioned binder was conducted. Experimental results showed significant changes in the properties of the binder after 9 months of water conditioning. Further, dynamic modulus of the mixes prepared with the binder conditioned for 9 months was significantly higher than the modulus of the unconditioned mix.