Analysis of Bituminous Crack Sealants by Physicochemical Methods: Relationship to Field Performance

Abstract

Bituminous crack sealants were analyzed by viscometry, fluorescence microscopy, infrared spectroscopy, thermogravimetry, modulated differential scanning calorimetry, and low-temperature tensile testing. The results indicate that sealants are blends of bitumen, oil, copolymer, and filler. Upon blending, these components produce a three-phase system that consists of a polymer-modified bitumen (PMB) matrix, a filler, and a filler-PMB interface. Spectroscopy and microscopy indicate that the PMB phase is rich in styrene-butadiene copolymer, that the filler is recycled rubber, sometimes mixed with calcium carbonate, and that the interface depends on the filler and the oil content in the sealant. The physicochemical methods were used to predict the short- and medium-term performance of sealant mixtures. The short-term performance predicted from viscometry and microscopy correlated well with the 1-year field performance of the sealants. Sealants showed two glass transition temperatures ( Tg’s), and a reasonable correlation was also found between low Tg and medium-term performance in a wet-freeze climate. However, because Tg measurements do not account for stress relaxation and aging effects, correlation was not perfect.