Methyl orange assisted dispersion of graphene oxide in the alkaline environment for improving mechanical properties and fluidity of ordinary portland cement composites

Abstract

Graphene oxide (GO) as a nano-reinforcing filler has great potential to improve the performance of cement-based composites, however, many challenges must be solved. Recent research has shown that GO tends to coagulate in the alkaline cement pore solution , limiting its reinforcement efficiency to improve the properties of cement composites . In this study, with polycarboxylic ether superplasticizer (PCE) as the main dispersant, methyl orange (MO) was further added to improve the dispersity of GO. The effect of MO on the dispersion of GO in saturated Ca(OH) 2 solution was investigated by UV-Vis spectrophotometer, Zeta potentiometer and atomic force microscope . Very low content of MO could significantly improve the colloidal stability of GO in CH solution and the optimal dispersion of GO was achieved when the mass ratio of GO to MO was 1:1. The effect of MO-dispersed GO on cement composites was investigated through mechanical strength analysis, microscopic analysis and chloride ion permeation analysis. The results showed that when the mass ratio was 1:1 and the content of GO was 0.03%, the 3d and 28d flexural strengths of cement mortar (0.03%-GO@MO) were increased by 27.4% and 15.4%, and the compressive strengths were increased by 21.8% and 15.3%, respectively, compared with the 0.03% GO-reinforced cement mortar(0.03%-GO). The chloride ion migration coefficient of 0.03%-GO@MO was 8.18%, lower than that of 0.03%-GO, which was caused by the denser internal structure of the former. Microscopic tests showed that the addition of MO could promote the dispersion of GO in cement pore solution, regulate the growth of cement hydration crystal and make the cement slurry structure denser. The addition of MO could reduce the loss of fluidity of the fresh slurry caused by GO. This study might provide a low-cost method to simultaneously improve the dispersion of GO in cement pore solution and the workability of GO-blended cement mortar and had many potential practical applications. • In the presence of PC, methyl orange could significantly improve the dispersion of GO in cement pore solution. • MO compensated the loss of the fluidity of the fresh cement slurry caused by the addition of GO. • Compared with GO-reinforced cement, the mechanical properties of MO@GO modified cement had been further improved. • The low-priced MO affords good dispersion of GO for the potential engineering application of cement-based composite.