EVALUATION OF THE EFFECT OF THE pH OF CONCRETE PORE SOLUTION ON THE CORROSION PERFORMANCE OF REINFORCING BARS

Abstract

In this study, the effect of the pH of concrete pore solution on the corrosion resistance of reinforcement is evaluated using the rapid macrocell test (outlined in Annex A2 of ASTM A955-14). Tests are conducted on five different types of reinforcing bars; Type 2304 duplex stainless steel bar, Type 304 stainless steel clad bar, MMFX Type CS (MMFX(9%)) reinforcing bar, galvanized reinforcing bar, and dual-coated reinforcing bar (zinc-coated bars covered with a layer of epoxy coating). Specimens are exposed to two different pore solutions (standard and modified) with pH values of 13.9 and 13.5, respectively, simulating the conditions found in concrete environments. The corrosion activity of the specimens is monitored using macrocell corrosion rate, corrosion potential, and microcell corrosion rate (as measured by linear polarization resistance measurements (LPR)). The results show that the pH of the pore solution (or of the concrete) has a major influence on the corrosion resistance of reinforcing bars. MMFX(9%) and dual-coated reinforcing bars exhibit better corrosion resistance in the standard pore solution compared to the modified pore solution. Conversely, the corrosion resistance of galvanized reinforcement decreases as pH increases, likely due to the formation of large isolated hydroxyzincate crystals. Stainless steel reinforcement generally exhibits similar corrosion resistance in the standard and modified pore solutions.