Experimental study on the effect of polycarboxylate-modified three-dimensional porous graphene on the microstructure and properties of ground granulated blast furnace slag-cement based materials

Ground granulated blast furnace slag (GGBS) is a well-established supplementary cementitious material known for improving the performance of cement-based materials, while reducing cement consumption and carbon dioxide emissions. However, it faces the issue of low early strength due to a delayed pozzolanic reaction. This paper aims to address this limitation by exploring the synergistic effects of a novel, polycarboxylate-modified threedimensional porous graphene (PCG) with GGBS to enhance the early strength of the cement-based materials. The methodology involved grafting carboxylic acid onto three-dimensional porous graphene (3DPG) using hydrochloric acid, which resulted in improved dispersibility of graphene in solutions. Macroscopic analysis revealed that PCG inclusion (from 0 to 0.1 wt%) increased the compressive strength and elastic modulus of the cementbased materials containing 20 wt% GGBS. Digital image correlation (DIC) showed that PCG slowed crack propagation and effectively minimized the number of cracks. Microscopically, nano-indentation tests indicated an increase in the packing density of hydration product calcium silicate hydrate (C-S-H) and an enhanced elastic modulus of C-S-H. Furthermore, the addition of PCG was found to increases the content of bound water and calcium hydroxide, confirming an accelerated rate of cement hydration. The results showed that the acceleration of cement hydration by PCG was most significant within the first 28 days, with diminishing effects thereafter. The increase in hydration products also enhanced the performance of GGBS volcanic ash activator and improved the capillary pores structure, significantly boosting the resistance of cement mortar to chloride ion diffusion.