Effect of multilayer graphene oxide on the hydration and early mechanical strength of cement mortar in low temperature

•MGO applied as the early strength agents in the low temperature.•MGO effectively compensate the early mechanical strength.•Nucleation effect of MGO accelerated the hydration reaction. The mechanical strength of cement mortar is normally decreased in a low-temperature environment, which is mainly due to the slow cement hydration reaction rate and an increase in the total pore volume, especially the harmful pore volume. With the modification of nano-materials, the early mechanical strength of cement-based materials can be effectively compensated. In this study, the effect of multilayer graphene oxide (MGO) on the early mechanical properties and microstructure of cement mortar at low temperatures of 0 °C, 5 °C, and 10 °C is studied by measuring the fluidity, setting time, mechanical property, scanning electron microscope (SEM), thermogravimetric (TG), and nitrogen adsorption/desorption test. Compared with the mechanical strength of control mortar with curing temperature of 20 °C, the mortars with the addition of MGO curing at low temperature present higher mechanical strength and denser microstructure. And the mechanism of the interaction between cement particles and MGO nano particles at low temperatures (0 °C, 5 °C, and 10 °C) is further discussed. The initial hydration reaction of MGO mortar is accelerated, which is mainly due to the nucleation effect of MGO and chemical reactions between –COOH on the edge of MGO nanosheets and the Ca2+ of Ca(OH)2. The promotion of the initial hydration refined the pore diameter of samples by reducing the pore size and total porosity, thus making the microstructure of samples denser and enhancing the strength of specimens.