Electrochemical and statistical analyses of the combined effect of air-entraining admixture and micro-silica on corrosion of reinforced concrete

This study aims to clarify the combined effect of air-entraining admixture (AEA) and micro-silica (MS) on the structure of cement mortar to improve the corrosion behavior of the resulting reinforced concrete. Open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and linear polarization resistance (LPR) tests were conducted on specimens after placing them in a 3.5% chloride solution. Scanning electron microscopy (SEM) imaging was also performed to characterize the surface porosity of the specimens. In addition, a comparison study with existing studies in the literature was performed to evaluate the accuracy of the obtained results. Moreover, a statistical analysis was performed using the extreme vertices mixture method to obtain the optimal value and contribution of each influential component. The results of the experiments indicate that using up to 0.7% AEA and 10% MS as a cement replacement provides the optimal combination among the mixes of the present study, as well as in comparison with existing studies. The results of the statistical analysis indicate that the optimal responses (i.e., maximum concrete resistance against penetration (R-c), electrical charge transfer resistance of the reinforcing bar (R-ct), polarization resistance (R-p), and minimum corrosion rate (CR)) are achieved for dosages of AEA and MS in the ranges of 0.60% to 0.69% and 9.31% to 9.40%, respectively. The results also show that the AEA dosage is more influential in improving the R-c, R-ct, and R-p, whereas MS dosage is more influential in reducing the CR. (C) 2020 Elsevier Ltd. All rights reserved.