| Significant distress characteristics that affect the performance of asphalt pavements are permanent deformation, fatigue, and low temperature cracking. Moisture damage is responsible for the loss of adhesion between aggregate and asphalt cement (stripping), and loss of cohesion of the asphalt cement matrix (softening). The combined effect of stripping and softening in asphalt mixtures is complex phenomena that manifest in two phases: stripping failure and loss of strength.; Performance graded asphalt binder (PG 58-28) was used in the preparation of the conventional and modified specimens. Characterization of materials and testing of the specimens were conducted according to the SHRP (Strategic Highway Research Program) protocol.; The mixtures were designed according to SHRP levels 1 and 2 protocol. Specimens were prepared at three levels of binder contents. Three specimens were tested at day zero and at days: 1, 4, 7, and 14 of immersion in water at 25°C and 40°C, respectively. The low and high temperatures represent average in-service and extreme conditions in the field. The durability potential of the specimens was evaluated by performance-based mechanical engineering properties generated from two performance based mechanical test ( static tensile test and repeated-load indirect tensile test).; Two durability indices were evaluated. The second index was more sensitive to losses of mechanical engineering material properties over the 14-day immersion period and was used as a quantitative parameter to characterize durability curves of conventional and modified mixtures.; The results of a one-sided lower t-test were significant at the 5 percent and 1 percent significant levels, hence, the null hypothesis of equal means between the dry conditioned and moisture conditioned specimens was rejected. A two-way analysis of variance of the combined effect of binder content and immersion time also resulted in rejection of the null hypothesis of no difference in means. In general, the rubber modified specimens exhibited superior durability to moisture damage than the conventional specimens, especially, at 40°C. |
