Effects of simulated groundwater solutions with different Ca2+ to Mg2+ concentration ratios on asymmetric electrodeposition in concrete

Electrodeposition is an emerging and unique method for the repair of concrete cracks, in particular, with great potential for the repair of aged asymmetric subsurface structures. However, the effect of groundwater solutions on the effectiveness of concrete repair by electrodeposition is not clear. Using an asymmetric electrodeposition repair device, this paper investigates the effect of simulated groundwater solutions with different Mg2+ to Ca2+ concentration ratios on the effectiveness of electric field-induced ettringite for repairing concrete cracks. Results show that the simulated groundwater solution has a negligible effect on the macroscopic repair effect on the electrolyte solution side, but allows a certain amount of Mg(OH)2 and CaCO3 precipitation to be generated on the simulated solution side. Meanwhile, compared with the deionized water group, the permeability coefficient is reduced from 2.05×10−6 cm/s to less than 7.65×10−7 cm/s at the repair age of 14 days. The total impedance is enhanced from 1322 KΩ to more than 1658 KΩ, with the lower the Mg2+ to Ca2+ concentration ratios, the lower the permeability coefficient and the higher the total impedance. Microstructure analysis suggests that as the concentration ratio of Mg2+ to Ca2+ decreases, the content of loose porous Mg(OH)2 decreases and the content of dense CaCO3 increases on the simulated solution side. Moreover, the size of the Mg(OH)2 particles on the simulated solution side, becomes larger and the amount of production decreases while the CaCO3 increases and changes from aragonite to calcite type.