Recycled concrete powder surface modification via graphene oxide for high performance, low carbon and cost-effective cement paste development

Reusing recycled concrete powder (RCP) significantly benefits construction resource recycling and environmental pollution reduction. However, the hydration activity of RCP is notably lower than that of cement, compromising the mechanical properties and durability. Therefore, this study proposes a surface-targeted modification strategy to coat graphene oxide (GO) onto the surface of RCP powders and verifies its feasibility through microscopic testing methods. The comprehensive impact on performance, pore structure, and economic and environmental benefits is systematically discussed. The results show that the proposed surface modification enables effective dispersion of GO nanosheets on the RCP powder surface while simultaneously enhancing the alkali activation of RCP. The coated-GO would adsorb the water and play a lubricating role between RCP and cement particles, thereby remarkably increasing the workability of the fresh RCP-cement composites by about 6.7-11%. Through nucleation and pore-filling effects, the coated-GO can refine and optimize the pore structure of recycled cement-based materials, thus strengthening the mechanical strength of recycled cement-based materials by 24.4-59.3% and reinforcing the chloride ion permeability resistance up to 49.6%. The economic and environmental benefits calculation further reveals that compared with plain cement, CO₂ emissions per ton of modified composites decline by about 28.7% (175 kg), and primary energy requirement drops by up to 28.5% (860 MJ) after mixing 30% GO-coated RCP. RCP surface modification not only significantly enhances material performance but also offers advantages such as low energy consumption, low carbon emissions, and low cost, providing a feasible path for the development of green, low-carbon cement-based materials.