Nowadays, corrosion evaluation of steel embedded in reinforced concrete (RC) plays an important role in repair, protection and maintenance of RC structures. Air-entraining agent (AEA) and microsilica (MS) are among the most important admixtures, which affect the corrosion rate (CR) of RC. Specifically, 12 mix designs incorporating different contents of AEA (ie, 0, 0.7, 1.4, 2.1, 2.9, and 3.6% by weight), half with 10% MS, were constructed. The corrosion behavior of RC specimens after exposure to 3.5% NaCl environment was investigated using halfcell potential (HCP) and electrical resistance (ER) as conventional tests and Tafel polarization as a more powerful corrosion test. Moreover, an optimization process was conducted on the mix design parameters using Taguchi and Factorial methods to analyze the effective factors and sensitivity of CR to each factor. The results of Tafel test indicate that they are noticeably more reliable and reasonable as compared to HCP and ER tests. Moreover, the results show that incorporating a low content of AEA (up to 0.7%) effectively improves the corrosion behavior of RC specimens, while the mix design containing 0.7% AEA together with 10% MS is the optimal design in terms of a decreased CR. The results also show that Factorial is a more applicable method in the field of corrosion evaluation of RC, due to the yield of more accurate findings as compared to Taguchi.

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