Characteristics of carbon black recycled from lightly pyrolyzed tire rubber and its impact on the high-temperature performance of asphalt

Waste cooking oil (WCO) is commonly used as an excellent reaction medium for the mild pyrolysis of ground tire rubber (GTR). Carbon black is a byproduct of rubber pyrolysis with varying properties depending on the pyrolysis process. To promote the utilization of pyrolytic carbon black (CBp) in asphalt modification, this study aims to characterize the low-temperature pyrolysis carbon black (LTCB) produced through the co-pyrolysis of GTR and WCO, and assess its impact on the high-temperature performance of asphalt. LTCB260 was separated by toluene extraction from the waste rubber-oil mixtures (WRO) containing the highest concentration of soluble substances. The identification of LTCB260 was conducted by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results indicated that the pure carbon black content in LTCB260 is 57.35 %, which is lower than CBp and N330. Bound rubber and inorganic salt crystals were observed to be randomly distributed on the surface of LTCB260. High-temperature performance tests conducted on asphalt indicated that the high-temperature deformation resistance of the LTCB260-modified asphalt was comparable to that of the other two carbon black-modified asphalts when using the same mass of carbon black. This suggests that despite being coated with impurities on its surface, the carbon black released from lightly pyrolyzed ground tire rubber still positively influences the high-temperature rheological properties of asphalt. However, when the carbon black content in WRO is significantly lower than that of the light component, the beneficial effect of carbon black on the high-temperature performance of asphalt may not be evident.