Insight into Ettringite Induced Concrete Crack Healing by Electrodeposition: Effects of Electrochemical Parameters and Numerical Simulations

The rapid healing of concrete through electrochemical deposition induced by ettringite has been recently proposed. In this paper, the rapid healing mechanism of this new approach is further disclosed via experimental investigations and numerical simulations. Nineteen groups of electrochemical deposition experiments are conducted with different electrochemical parameters. When the concentration ratio of calcium-aluminum is 2.5 and the current density is 2.0 A/m2, cracks can be healed within a day, with a permeability coefficient of 7.02 x 10-7 cm/s achieved at 7 days. Upon increasing the current density, the ettringite crystal gradually changes from fine needle-like to slender fibrous, and the deposited materials demonstrate refined pore sizes, with the highest proportion found in the 2-50 nm range. Meanwhile, the repair process is quantitatively demonstrated by incorporating the numerical model of the ion transport and the nucleation theory together. When the calciumaluminum ratio is 2.5, the average nucleation frequency of ettringite is maximized, indicating the most favorable repair effect. Compared to the deposition products Zn(OH)2 and Mg(OH)2, ettringite exhibits higher values of nucleation frequency, enabling a more rapid repair effect.