Employing novel N-doped graphene quantum dots to improve chloride binding of cement

One of the most primary reasons for durability deterioration of reinforced concrete (RC) structures is reinforcement corrosion caused by chloride ion invasion. However, there is still a lack of efficient additives to enhance the anti-chloride-corrosion behavior of RC structures. Herein, highly dispersed and cost-efficient N-doped graphene quantum dots (N-GQDs) are firstly applied to significantly increase the chloride binding performance of cement. Specifically, N-GQDs with high dispersity and low cost are successfully synthesized by one-step hydrothermal method. And the typical equilibrium test determines that after 14-day exposure to 3 M NaCl solution, the incorporation of 0.2 wt% (by weight of cement) N-GQDs makes the chloride binding ability of cement paste sharply boost by 134%. Moreover, in light of phase compositions analyses from XRD, TGA and SEM, the chloride binding mechanism of cement pastes modified by N-GQDs is rationally ascribed to the fact that the addition of N-GQDs enormously increases the physically adsorbed chloride ions and slightly promotes chemically bound chloride ions. This work firstly provides a novel carbon-based nanomaterial to efficiently enhance the chloride binding of cement, expected to improve the durability of RC structures.