A novel and promising engineering application of carbon dots: Enhancing the chloride binding performance of cement

Corrosion of reinforcement induced by chloride invasion is extensively considered as the dominating deterioration mechanism of reinforced concrete (RC) structures, leading to serious safety hazards and tremendous economic losses. However, it still lacks well dispersive and cost-efficient nanomaterials to improve the anti-chloride-corrosion ability of RC structures. Herein, specific carbon dots (CDs) with high dispersity and low cost are deliberately designed, successfully prepared by hydrothermal processing, and then firstly applied to immensely enhance chloride binding performance of cement, thereby contributing to suppressing the corrosion of reinforcement. Specifically, the tailored CDs are composed of the carbon core with highly crystalline sp2 C structures and oxygen-containing groups connecting on the carbon core; The typical equilibrium test confirms that with respect to that of the blank cement paste, the chloride binding capacity of cement paste involving 0.2 wt.% (by weight of cement) CDs is increased by 109% after 14-day exposure to 3 mol/L NaCl solution; according to comprehensive analyses of phase compositions, the chloride binding mechanism of CDs-modified cement is rationally attributed to the fact that the incorporation of CDs advances the formation of calcium silicate hydrate (C–S–H) gels and Friedel's salt (Fs), thus enormously enhancing the physically adsorbed and chemically bound chloride ions of cement pastes. This work not only firstly provides a novel high-dispersity and low-cost nanomaterial toward the durability enhancement of RC structures, but also broadens the application of CDs in the field of engineering, conducing to stimulating their industrialization development.