A novel ultrasonic method to exfoliate CLDH toward improving mechanical and chloride binding properties of cementitious composites

With the complexity of architectural structures increasing, traditional cement-based materials inevitably face challenges of mechanical performance and durability. Calcined layered double hydroxide (CLDH) attracts significant attention due to its potential for improving mechanical and chloride binding properties of cement-based composites, but suffers from poor dispersion, limiting its full potential. To tackle this issue, a novel method utilizing graphene quantum dots (GQDs) in conjunction with ultrasound has been developed to efficiently exfoliate CLDH, thereby enhancing the mechanical and chloride binding properties of cement composites. Most importantly, its related enhancement mechanisms were revealed by comprehensively analyzing hydration heat evolutions, phase compositions, and microstructures of relevant cement samples. Specifically, highly dispersed CLDH (G-CLDH) prepared by GQDs-assisted ultrasonication possessed a larger specific surface area (SBET), significantly increasing by 92.04 % compared with CLDH treated by pure ultrasonication (i.e., U-CLDH). After incorporating 0.8 wt.% (by weight of cement) G-CLDH, the cement composites demonstrated 22.29 % and 58.56 % improvement in compressive strength and chloride binding capacity respectively than blank group. The enhancement mechanism of compressive strength and chloride-binding capacity by G-CLDH was rationally proposed. As for the former, it was attributed to a significant reduction of porosity and a remarkable increase of hydrated calcium silicate (C-S-H) gels; Regarding the latter, that was a larger number of C-S-H gels and better dispersed G-CLDH led to more physically adsorbed chloride and more ion-exchanged-caused bound chloride respectively. The developed innovative approach could prepare high-dispersion CLDH to simultaneously enhance mechanical performance and chloride binding capacity of cementitious materials, promoting to the advancement of high-performance cement composites.