Aging mechanism of hot-poured sealants for asphalt pavement under natural environmental exposure

Extended exposure of crack sealant to the natural environment causes a gradual degradation of its properties owing to aging with complex mechanisms. Two types of sealants were directly exposed to natural environment to investigate the aging effects on the sealant properties. In comparison with the original sealant, the surface of the aged sealant gradually hardened, embrittled, and darkened, while numerous cracks with different depths and widths appeared during aging. Fourier transform infrared spectroscopy, confocal laser scanning microscopy, differential scanning calorimetry, and three conventional properties of sealants were employed to discuss the micro- and macro-performance differences and mechanism before and after three-month-aging. Experimental programme results show that age-conditioned sealants cause a clear increase in sulphoxide and carbonyl compared with the unconditioned ones. During the aging process, the polymer particles degraded, and the base asphalt in the sealant has undergone fateful aging. The endothermic peak values of sealants in the differential scanning calorimetric curves become wide, particularly two endothermic peaks are observed after aging. This phenomenon suggests that the sealant properties become unstable after aging. Cone penetration dramatically declines while the softening point increases after aging. The two sealants are in the glass state under the low-temperature tensile test environment after aging.