Characterization of crumb tire rubber lightly pyrolyzed in waste cooking oil and the properties of its modified bitumen

Abstract

Crumb tire rubber (CTR) is one of the most common bitumen modifiers used to improve bitumen rheological properties. However, the rubberized bitumen has shown poor storage stability and workability in the application which affect the service performance of the pavement. This work investigated the feasibility of application of waste rubber/oil (WRO) produced by light pyrolysis of CTR in waste cooking oil as a bitumen modifier. The chemical properties, thermal behaviors and reaction process of WRO were characterized by gel permeation chromatography, Fourier transform infrared spectroscopy and TGA/DSC synchronous thermal analysis. The thermodynamic parameters of WRO were calculated by TGA/DTG data, and the thermal stability of WRO was analyzed. The storage stability, physical and rheological properties of WRO modified bitumen and rubberized bitumen were evaluated by separation test, conventional tests and rheological tests, respectively. Results show that, the chain scission and depolymerization occur in the cross-linked network structure of CTR after light pyrolysis, which result in the reduction of rubber hydrocarbon content in gel CTR and the molecular weight of CTR. Natural rubber appears in the sol of the lightly pyrolyzed CTR, and the content of the oxygen-containing functional groups in the sol increases. The thermal behaviors of WRO become complicated, and thermal stability is enhanced from the apparent active energy. Compared to rubberized bitumen, the storage stability, plasticity at low temperature and workability of WRO modified bitumen are greatly improved. However, the resistance to rutting and deformation at high temperature become worse. Further study will be conducted to enhance the high temperature performance with additional additives.