Multivariable Empirical Analysis of Coupled Oxygen and Moisture for Potential and Rate of Quantitative Corrosion in Concrete

Abstract

Qualitative as well as quantitative effect of oxygen on the corrosion of reinforced concrete structures under various environments and compositions has been successfully obtained through extensive multivariable laboratory experimentation in this research for which the previous research data is limited and has difference of opinion. The experiment results of this research showed that the diffusion of oxygen is not an influential factor for corrosion inhibition as long as the reinforced concrete is not placed completely under water even in very high humidity environmental conditions as much as 95% relative humidity. The only exception is when the diffusion path of oxygen from the surface of concrete to the depth of steel reinforcement is extended and made slender enough by using a thick concrete cover and low water/cement ratio to make the coefficient of oxygen comparable to that of submerged condition which is not a normal practice. In all cases of relative humidity less than one hundred percent, the diffusivity of concrete is never less enough to make the system oxygen diffusion controlled. This finding is also quantified in this research in terms of concrete cover depth and water/cement ratio in relation to half-cell potential and corrosion rate by using a variety of material and environmental variables. The extensive results of this research can also be used for detailed calibration of underwater half-cell potential measurements which were observed as not the true representative values of corrosion progress showing extremely negative half-cell potential values due to underwater reduced resistivity of concrete.