Effect of graphene oxide on rheology, hydration and strength development of cement paste

The aim of this paper is to investigate the effect of a well-dispersed graphene oxide (GO) on workability, rheological properties, hydration kinetics, density of hydration products, and compressive strength of cement paste. Paste mixtures were prepared with 0.42 water-to-cement ratio, and a well-dispersed GO was incorporated at contents of 0.04%, 0.15%, and 0.29%, by mass of cement. When coupled with sonication time of 48 to 56 min, the optimum active superplasticizer (SP) dosage was found to be four times that of the GO. Compared to paste made with 0.16% SP and no GO, the addition of 0.04% GO increased yield stress and viscosity coefficient values of paste, total heat of hydration at 70 h, density of hydration products at 28 d, and compressive strength at 1, 3, and 7 d. The increase in rheological properties can be caused by the reduction in free water due to water absorption by the GO, while the increase in total heat and compressive strength can be associated with the nucleation effect of the GO. However, increasing the GO content from 0 to 0.15% with the SP dosage fixed at a higher dosage of 0.6% showed no effect on hydration kinetics but reduced yield stress, viscosity coefficient, and 1-d compressive strength. This behavior was attributed to the high dosage of the SP needed for dispersing the high content of GO. The beneficial effect of using 0.15% GO was evident from the increase in compressive strength at 3 and 7 d. Overall, the addition of well-dispersed GO improved the rheological properties, hydration kinetics, density of hydrates, and compressive strength of cement paste. However, the improvement achieved with GO at early age (1 d) was hindered by the retarding effect of SP used to maintain proper dispersion. (C) 2020 Elsevier Ltd. All rights reserved.