Investigation of dispersion behavior of GO modified by different water reducing agents in cement pore solution

Graphene oxide (GO) is an attractive candidate for use as a nano-reinforcement in cement composites. However, a prerequisite for GO to fulfill its function is the uniform dispersion of GO throughout the cement matrix. In this paper, the dispersion behavior of GO modified by lignosulfonate (LS), polycondensate of β-naphthalene sulfonate formaldehyde (PNS), and polycarboxylate superplasticizer (PC) in cement pore solution was investigated by a combination of visual observation, optical microscopy and transmission electron microscopy (TEM). Results show that GO modified by PC exhibited better dispersion in cement pore solution than LS and PNS. Zeta potential analysis demonstrated that LS and PNS failed to adsorb onto the GO surface when pH > 11, while successful attachment of PC to GO was achieved even in the alkaline environment. The dispersion mechanisms of PC modified GO were thought to be a combination of covering the surface of GO, lowering the free Ca2+ concentration and impeding the cross-linking of Ca2+ due to steric hindrance effect of PC. With the addition of PC modified GO, the fluidity and mechanical strength of cement composites were improved significantly, indicating that this dispersion route can be successfully used for the preparation of GO reinforced cement composites.