Effects of Chemically Modified Three-Dimensional Porous Graphene for the Optimal Rheology and Mechanics of Cement Composite

Abstract

Although graphene significantly enhances the performance of cement-based materials, its tendency to agglomerate in strongly alkaline cement paste environments and its high cost limit practical applications. To overcome these challenges, this study employed polycarboxylate (PC) to covalently modify three-dimensional porous graphene (3DG), producing polycarboxylate-modified 3DG (PG), aimed at effectively improving cement-based material performance at an extremely low dosage. At the optimal dosage (0.03% by mass of cement, corresponding to a graphene content of 0.01% within PG), experimental results demonstrate that PG exhibits superior dispersibility and stability compared to unmodified 3DG, both in solution systems and within cement paste. Furthermore, the incorporation of PG slightly reduced the yield stress and plastic viscosity of the cement paste. Hydration heat analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM) confirmed that PG effectively accelerated the hydration reaction and densified the microstructure. Compared with the paste without graphene, the incorporation of PG enhanced the compressive strength by 30.8%, 28.8%, and 26.4% at 3, 7, and 28 days, respectively. Concurrently, mercury intrusion porosimetry (MIP) analysis revealed that the homogeneous dispersion of PG effectively inhibited the formation of large pores, leading to reductions in total porosity by 21.9%, 19.6%, and 23.4% at the corresponding ages while simultaneously optimizing the pore size distribution. These improvements in pore structure collectively contributed to the enhanced resistance of the cement paste to chloride ion diffusion.