Effects of polycarboxylate superplasticizer-modified graphene oxide on hydration characteristics and mechanical behavior of cement

Graphene oxide (GO) has received great attention as a nanosized reinforcing agent in cement-based materials. However, GO easily aggregates in an alkaline cement matrix and suffers from poor dispersibility, which reduces the beneficial effect on the final properties of cement composites. In this study, GO-polycarboxylic acid superplasticizer (GPC) was synthesized by free-radical copolymerization of GO with methyl allyl polyoxyethylene ether (TPEG), sodium styrene sulfonate (SSS) and acrylic acid (AA). The chemical structure of the GPC was characterized by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). To understand the influence of GO on the cement hydration process, we analyzed hydration heat, phase composition, and TG/DSC behavior. The pore structure and micromorphology of the cement composites were investigated by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). The results showed that the GO layer spacing increased after copolymerization, and the GO surface was covalently grafted with PC macromolecules. The addition of GPC to cement yields uniform dispersion of GO and reduces the adverse effects of GO on the fluidity of the cement slurry. GPC can accelerate cement hydration, promote crystallization of calcium hydroxide (CH) in the cement slurry, refine grain size, and enhance mechanical properties of the cement-based materials.