Harmless treatment and environmentally friendly application of waste tires—TPCB/TPO composite-modified bitumen

•The harmless treatment and utilization of waste tires is promoted.•Bitumen was composite-modified by TPO and TPCB.•The design and preparation parameters of TPO/TPCB-MB were determined.•TPO can balance the components and recover the TPCB’s effects on the properties of bitumen.•Road properties of TPO/TPCB-MB and its mixture were not worse than 70# bitumen. Waste tires are produced in large quantities and cause serious pollution. Moreover, it is challenging to dispose of waste tires safely. Pyrolysis treatment is an economic, environmentally friendly, and high-recovery-efficiency solution, but the recycling applications of pyrolysis products, such as pyrolysis carbon black (TPCB) and pyrolysis oil (TPO), have not been widely studied. In this study, TPO and TPCB were applied to composite-modify 70# base bitumen. The modification mechanism of TPO/TPCB-modified bitumen (TPO/TPCB-MB) was studied by Fourier transform infrared spectrometry (FTIR), gel-permeation chromatography (GPC), X-Ray diffraction (XRD), and scanning electron microscopy (SEM). The physical performance and rheological performance of the bitumen with and without TPO/TPCB were investigated to determine the design and preparation parameters of TPO/TPCB-MB and investigate TPO/TPCB’s effects on the technical performance of bitumen. In addition, the road performance of TPO/TPCB-MB concrete was extensively studied. In the results, no large agglomeration phenomenon was observed between the TPCB particles. Furthermore, the molecular weight of TPO was much lower than that of 70# bitumen, indicating that TPO can increase the light components of bitumen. TPCB and TPO mixed with the bitumen in a physical manner, and the multi-layer spacing of TPCB remained basically unchanged. The TPO/TPCB was also shown to have good thermal and structural stability. TPO and TPCB, moreover, provided component balance and powder hardening effects in the TPO/TPCB-MB. No significant difference was observed between the technical performance of the 70# bitumen and the 0.9% TPO + 15% TPCB-MB. The water stability, low-temperature, and anti-fatigue performance of the TPO/TPCB-MB mixture was significantly better than that of the 70# bituminous mixture. Meanwhile, the high-temperature performance showed no obvious difference. Therefore, TPO was found to balance TPCB’s oppositive effect on the performance of bitumen and its mixture. The composite modification of bitumen with TPCB and TPO thus represents a harmless treatment and altern