Electro-deposition of silicate ions for crack-healing performance in concrete

To address the limitations of conventional crack-repair methods for concrete structures in aqueous environments, a novel electro-deposition technique using silicate ions (SiO₃²⁻) was proposed. Under an externally applied electric field, SiO₃²⁻ from the electrolyte and calcium ions (Ca²⁺) from the concrete pore solution migrated toward the crack site and reacted to form insoluble compounds that effectively sealed the crack. The crack-repair efficiency was evaluated under different silicate concentrations (0.05, 0.10, 0.20 and 0.50 mol/l), applied voltages (24, 48 and 96 V), crack widths (0.3 and 1.0 mm) and crack depths (12 and 18 mm) using the mass-increase rate, crack-healing rate and permeability coefficient as indicators. The microstructure and composition of the deposits after the electro-deposition treatment were characterised using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. The experimental results showed that the optimal crack-repair performance was achieved at a silicate concentration of 0.05 mol/l and an applied voltage of 48 V. Cracks with smaller width and greater depth exhibited superior repair effectiveness under these optimal conditions. The main components of the deposited materials were calcium carbonate and calcium silicate hydrate gel, and the microstructure evolved from a loose to a dense morphology over time.