Reinforcing bitumen with highly graphitized reduced graphene oxide derived from coal Tar pitch via template free sole step hydrothermal strategy

This study pioneers a cost-effective and scalable technique for preparing high-quality, highly-graphitized reduced graphene oxide (HG-RGO) from coal tar pitch (CTP), as an abundant aromatic precursor. The novelty lies in developing a one-pot, hard template-free hydrothermal method utilizing cetyltriethyl ammonium bromide (CTAB) at a moderate temperature, 270 °C to facilitate the formation of the desired nanostructure. Comprehensive microstructural analysis, utilizing XRD, FTIR, Raman spectroscopy, HR-TEM, and SAED patterns, confirmed the successful preparation of HG-RGO. This HG-RGO was then utilized to modify bitumen (penetration grade 80/100) at varying concentrations (1 wt%, 3 wt%, and 5 wt%) to create graphene-modified bitumen (GMB). The study meticulously assessed the impact of HG-RGO on the physical and mechanical properties of both the bitumen binder and the resulting asphalt mixtures. The results unequivocally demonstrate that HG-RGO acts as a potent modifier, effectively upgrading the soft bitumen pen grade 80/100 to the harder pen grade 60/70. Key physical property improvements were quantified: the Softening Point increased by 10 to 55 °C, the Penetration degree decreased by 17 to 68dmm, and Kinematic Viscosity increased by 200cSt to 550cSt.Furthermore, the HG-RGO significantly enhances the mechanical characteristics of the asphalt mixtures. The Marshall Stability reached a maximum of 2200 kg for the 5wt% GMB mixture, and the rutting depth decreased threefold compared to the unmodified binder, reaching just 5 mm for GMB5. Dynamic Mechanical Analyzer (DMA) results confirmed improved rutting resistance at high temperatures and enhanced fatigue performance, evidenced by decreased loss modulus. These findings suggest that HG-RGO can be successfully utilized as a modifier for soft bitumen for pavements like traditional bitumen pen grade 60/70.