Degradation behavior and self-healing mechanism of force-Cl- triggered microcapsule/ cementitious composites

Abstract

The performance of microcapsules in terms of “chloride response” and their electrochemical remediation mechanism is investigated. Electrochemical testing methods are used, i.e., kinetic potential polarization and electrochemical impedance testing. The variation rules of corrosion behavior of self-healing cementitious composites with different contents of microcapsules, both intact and pre-damaged, were investigated in a chloride ion environment. Based on this, the equivalent circuit change model is established. By fitting the parameters of the circuit elements, the change rule of the fitted parameters of the circuit elements is derived. To analyze the internal changes of self-healing cementitious composites in the corrosion process, and to reveal the self-healing mechanism of self-healing cementitious composites on the protective effect of its internal steel reinforcement. It was shown that the corrosion current density could be reduced as low as 0.87 μA/cm² for the intact samples immersed for 3 days and as low as 1.95 μA/cm² for damaged samples. The self-healing cementitious composites remained protective of the internal reinforcement after 56 days of immersion; Studies on the electrochemical self-healing mechanism have shown that microcapsules improve corrosion protection based on increasing the electrical resistivity of cementitious composites. The addition of 9 wt% microcapsules provided up to 39.16 % restoration efficiency at 56 days of immersion, and the restoration efficiency increased to up to 55.62 % in response to the combination of cracks and chloride ions. The microcapsules act together through mechanical and chloride ion response to retard the corrosion rate of steel reinforcement inside the self-healing cementitious composite by protecting the reinforcement passivation film.