Application of a Biomodifier as Fog Sealants to Delay Ultraviolet Aging of Bituminous Materials

This study examines the merits of applying a biomodifier (Bio-binder, Sustainable Infrastructure Material Lab, NC A&T State University, Greensboro, North Carolina) as a fog sealant on the surface of bituminous materials to delay aging specifically caused by ultraviolet (UV) radiation during pavement service life. This study uses four types of bituminous-based materials: an asphalt binder [Performance Grade (PG 64-22) and three types of crack sealants with varying polymer content and different viscosities. Materials were prepared in small samples on aluminum plates and aged under continuous UV and UV/moisture/condensation conditioning. Changes in the chemical characteristics of the materials were then analyzed using Fourier-transform infrared spectroscopy and energy-dispersive X-ray spectroscopy. The results show that the oxygen uptake of bituminous materials after exposure to UV aging are significantly lower in specimens covered with Bio-binder compared with uncoated ones. The complex modulus and creep compliance were measured using a dynamic shear rheometer. The complex modulus for asphalt binder samples showed an increase that could be due to partial diffusion of the biomodifier in the specimens. However, in sealant samples in which the Bio-binder was removed prior to performing the experiments, the shear modulus showed a significant decrease, indicating that the sealants covered with Bio-binder remained softer compared with the uncovered samples. The results also showed a higher nonrecoverable creep compliance and a lower percent recovery at 3.2kPa strain rate for specimens coated by Bio-binder compared with the samples with no coating, showing that the fog sealant can effectively improve properties of the sealant samples. Overall, the findings demonstrate that Bio-binder can be a promising candidate to be used as a fog sealant for bituminous binder and crack sealants to delay UV aging. (C) 2018 American Society of Civil Engineers.