Property characterization of asphalt binders and mixtures modified by different crumb rubbers

This study focused on the property characterization of asphalt and asphalt mixtures modified by different types of crumb rubber (normal and desulfurized). This characterization was based on chemical evaluation and property testing for rubber asphalt and on performance analysis for different rubber asphalt mixtures. Chemical fraction and gel permeation chromatography tests were used to identify rubber asphalt's microstructures; conventional and Superpave property tests were performed to evaluate its macroproperties; and an isolation test was used to judge its storage stability. Also conducted were wheel loading tests, three-point beam bending tests, and Marshall tests along with splitting tests and four-point beam bending tests to evaluate rutting stability, thermal cracking resistance, water damage susceptibility, and fatigue cracking resistance in different rubber asphalt mixtures. The findings indicate that both normal and desulfurized crumb rubber have obvious positive impacts on the properties of neat asphalt and asphalt-rubber mixtures. Compared with normal crumb rubber asphalt (NCRA), desulfurized crumb rubber asphalt (DCRA) shows lower viscosity and better storage stability. Both the normal crumb rubber asphalt mixture (NCRAM) and the desulfurized crumb rubber asphalt mixture (DCRAM) exhibit good properties. However, whereas NCRAM production uses gap gradation along with greater asphalt content and higher production temperatures, DCRAM production uses dense gradation with less asphalt content and lower production temperatures, making it more similar to the Styrene-Butadiene-Styrene (SBS) modified asphalt mixture.