Targeted modification of self-healing microcapsules with CLDH/SiO2 for enhanced corrosion inhibition: Experimental and theoretical calculation

Functional materials represented by calcined layered double hydroxide (CLDH), nano-silica (SiO 2 ), and microcapsules are frequently incorporated into cement-based composites to accelerate cement hydration or autonomously heal matrix microcracks, thereby enhancing the chloride-binding quantity and inhibition performance of cementitious system. In this work, CLDH and SiO 2 were employed to target modify microcapsules (CLDH/SiO 2 -MC), aiming to achieve the functional coupling effects of three materials. The study revealed that CLDH and SiO 2 were successfully anchored within the microcapsule wall and improved the surface roughness of modified microcapsules. The targeted modification strategy is beneficial to improve the interfacial bonding between microcapsules and cement paste. Interestingly, the alkaline pore solution induced the hydration reaction of active SiO 2 component within the surface of modified microcapsules. Compared with the reference group, cement paste specimens incorporating 3 % and 6 % microcapsule demonstrated 30.76 % and 53.85 % enhancements in chloride binding capacity, respectively. The D RCM values of cement mortar with CLDH/SiO 2 -MC additions of 0 %, 3 %, 6 %, and 9 % were 19.95, 14.63, 17.00, and 19.52 × 10 −12  m 2 /s, respectively. The synergistic corrosion inhibition effects of microcapsules resulted in higher R ct value of steel electrode, and the highest inhibition efficiency of CLDH/SiO 2 -MC was 97.84 %. The density functional theory (DFT) calculations show that the charge exchange capacity between CLDH/SiO 2 and ethyl cellulose is 2.36 e – , with metal atoms serving as electron donors. The CLDH/SiO 2 targeted modified microcapsules achieved synergistic corrosion inhibition through self-healing of the core, chloride binding and pozzolanic activity of the wall, which is helpful to realize the sustainable development of steels.