Reaction mechanism and rheological properties of waste cooking oil pre-desulfurized crumb tire rubber/SBS composite modified asphalt

Abstract

Waste cooking oil (WCO) is proved to be effective in desulfurization of crumb tire rubber (CTR), which can be considered as a sustainable desulfurization technology and an alternative way to solve the poor storage stability of asphalt rubber. However, WCO pre-desulfurized CTR (ODR) modified asphalt displays a compromised high-temperature performance, leading to a limited application of ODR in asphalt modification. In this study, ODR/styrene–butadiene-styrene (SBS) composite modified asphalt was developed to make up the loss of high-temperature performance. The reaction mechanism of ODR/SBS composite modified asphalts with and without sulfur was investigated via Fourier transform infrared spectroscopy (FTIR), gel permeation chromatograph (GPC) and fluorescence microscope (FM). Rheological tests were conducted to clarify the effects of ODR, SBS and sulfur on the rheological behavior of the modified asphalt. FTIR, GPC and FM results proved that crosslinking reaction occurred during the composite modification of ODR, SBS copolymer and base asphalt in the presence of sulfur with moderate content, forming a continuous and homogeneous microstructure with a significantly increased large molecular weight, which is less prone to produce phase segregation. The ODR composite modified asphalt with 3 wt% SBS and 0.4 wt% sulfur presents the best rutting resistance due to the increase of the elastic network structure and cracking resistance due to the presence of WCO and the released rubber chain. The above composite modified asphalt meets the standard traffic level at 76 °C and the specification at −34 according to the multiple stress creep recovery and bending beam rheometer tests.