Understanding moisture damage mechanisms in asphalt pavements and evaluating the right combination of materials that are resistant to moisture damage are important. Moisture damage is the loss of strength or stiffness in asphalt mixtures caused by a combination of mechanical loading and moisture. Many test methods have been developed to evaluate loss of adhesion and cohesion in binders. However, a simple procedure to address moisture damage in the asphalt–aggregate interface is not available. The feasibility of the newly developed bitumen bond strength (BBS) test for moisture damage characterization was investigated. An experimental matrix that included various binders, modifications, and aggregates to account for the chemical and physical conditions in the aggregate–asphalt interface was completed. A statistical analysis was performed to verify reproducibility of the BBS test. The results indicated that the bond strength of asphalt–aggregate systems was highly dependent on modification and moisture exposure time. Polymers were found to improve the adhesion between asphalt and aggregate as well as the cohesion within the binder. Results from this study indicated that the BBS test was repeatable and reproducible. To further validate the effectiveness of the BBS test, a comparison of the BBS test results and the modified dynamic shear rheometer strain sweep test was conducted. The comparison showed that the BBS test could rank materials similarly to a more sophisticated and time-consuming test.

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Aging of asphalt binders is induced by chemical or physicochemical changes during production of pavement and throughout its service life. Although binder aging in pavement always occurs while binders are in contact with aggregates and mineral filler, in most laboratory aging studies and in current specifications, asphalt binders are individually aged without accounting for aggregate induced interactions. Past research has had conflicting findings, as it attributes mitigating or catalytic effects to the presence of mineral fillers in asphalt binders with oxidative aging. Thus, in the present study it was hypothesized that evaluation of asphalt oxidative aging without taking into account the interactive effect of the presence of mineral fillers was inadequate as a specification tool. The effect of mineral fillers on oxidative aging of asphalt was investigated with accelerated aging of mastics (asphalt and fillers) in a pressure aging vessel (PAV) and by measuring the changes in stiffness and glass transition temperature ( Tg). The testing matrix included an aging evaluation of mastics containing different fillers, mineralogy, and surface area. The results showed that the low-temperature behavior of aged mastic could be modified by controlling filler concentration and type. The fillers acted as an agent adsorbing heavy fractions of asphalt binder and therefore reduced stiffness and changing Tg. During oxidative aging of asphalt binders and mastics, diffusion and adsorption mechanisms played a role in the rate of aging of asphaltic material. The results provided insight on the potential for selecting a mineral filler concentration and mineralogy type to reduce the impact of oxidative aging and possibly improve the service life of pavement.

Oxidative aging causes hardening of asphalt binders and, consequently, contributes to the deterioration of asphalt pavements. The principal cause of asphalt aging and embrittlement in service is the atmospheric oxidation of molecules with the formation of highly polar and strongly interacting functional groups containing oxygen. Therefore, aging is a complex process in unmodified asphalt binders, and the complexity increases for modified binders. The dynamics of world resource economics suggest that the asphalt pavement industry should be exploring economically and environmentally sustainable approaches to development, such as the addition of recycled oils to the base asphalt binder, and thus research activities are noteworthy in this area. The effect of oil and polymer modification on asphalt binder rheology and oxidative aging has become a popular topic for research in recent years. However, the effects of oil and polymers are often studied independently. The objective of this study was to investigate the modification effects of bio-oil, re-refined wasted engine oil, polymers, and the interaction between polymers and oil on the aging susceptibility of asphalt binders. After laboratory accelerated aging procedures were conducted, dynamic shear rheometer and bending beam rheometer tests were used for the rheological performance evaluation. Gel permeation chromatography and Fourier transform infrared spectroscopy were used to verify the rheological results with chemical analysis tools. Results indicate that the aging susceptibility of modified asphalt binders is dependent on modification chemistry. Certain polymers and combinations of polymers with oil can reduce the base asphalt binder’s susceptibility to aging.