Low-cost in-situ preparation of highly dispersed graphene for high-performance cement-based composites

Graphene (G) has gained much attention as a promising nano-reinforcement for cement. Despite the potential, challenges persist owing to their inadequate dispersion in cement matrices and high production costs. Developing a graphene-based cement material that is cost-effective and has graphene uniformly dispersed in the cement matrix remains an urgent problem. In this paper, chemical vapour deposition (CVD) was used to promote the conversion of waste coffee grounds into graphene on the surface of iron tailings powder (ITP) (G@ITP) by using waste coffee grounds as a cheap carbon source and ITP, a waste residue from iron tailings processing, as a reaction substrate. Microscopic morphology and structure characterization revealed that the graphene generated using this method disperses well in the cement matrix, aiding the hydration process and creating a denser microstructure. In addition, the method promotes effective utilization of resources from solid waste and reduces the cost of preparation. It was concluded that the compressive and flexural strengths of the G@ITP test group prepared in-situ under optimum conditions (i.e., 850 degrees C, 3 wt% carbon source) were increased by 50.1 % and 58.7 %, respectively, and the water absorption was reduced by 16.4 % (28 d of curing) compared to that of the pure cement paste. Apart from that, the G@ITP composites considerably decreased the carbonation depth and retarded the carbonation process of cement paste at different carbonation ages (3d, 14d, 28d). Moreover, G@ITP reinforced cementitious composites have superior mechanical properties and durability compared with cementbased composites made from ultrasonic and surfactant dispersed commercial graphene. This study opens up a new avenue for G@ITP as a nano-reinforcing material applied to cement composites, which offers tremendous possibilities in realizing multifunctional applications of cement materials.