Performance Characterization and Combination Design Optimization of Fast-Melting Sbs/Cr Modified Asphalt

Abstract

The fast-melting styrene-butadiene-styrene modifiers (F-SBS) exhibit rapid dissolution in asphalt, reducing mixing time and energy consumption, and significantly enhancing asphalt properties. The use of crumb rubber (CR) in asphalt can lower costs and address resource problems. This study used CR to replace part of the F-SBS to prepare the fast-melting SBS/CR modified asphalt (F-SCMA). Firstly, rheological tests were carried out on fast-melting SBS modified asphalt (F-SBSMA) with different dosages of F-SBS (3.0%, 3.5%, and 4%). Then, the high- and low-temperature continuous performance grade (PG) of F-SCMAs were characterized by DSR and BBR tests. The recommended dosage of F-SCMA was further determined by the Brookfield viscosity, the linear amplitude sweep (LAS), and the softening point difference tests. Finally, the microscopic mechanism of F-SCMAs was characterized by Fourier transform infrared spectroscopy (FTIR) and fluorescence microscope (FM) tests. The results indicated that F-SBS significantly enhanced the rheological properties of neat asphalt (NA). The PG of asphalt containing 3.5% SBS was PG 76-28, and it had the most significant modification effect among different dosages of F-SBSMA. The modified asphalt containing 2.5% SBS + 6% CR had a higher continuous PG, better temperature sensitivity, and anti-fatigue properties compared to 3.5% F-SBSMA. 3S+4R and 1S+8R had the most excellent high- and low-temperature properties, respectively. Furthermore, FTIR and FM tests revealed that F-SBS and CR were modified in asphalt with a physical mixing process, and the two modifiers were compatible with the NA. This study can provide design concepts for various F-SCMA applications and a theoretical foundation for enhancing the overall properties of F-SCMA.

Keywords: Fast-melting SBS, SBS/CR modified asphalt, rheological properties, Microscopic mechanism