Influence of connectivity of concrete pores and associated diffusion of oxygen on corrosion of steel under high humidity

This paper investigates the limitation of oxygen diffusion under high relative humidity condition in comparison to submerged, alternate wetting-drying and air dry conditions and its influence on the corrosion rate of steel by blocking the pores of concrete with moisture and reducing the connectivity required for transfer of gaseous oxygen from the environment to the steel bar surface. This was achieved through multi-variable experimentation for which the previous research is limited and has difference of opinion. It is concluded from the observed trend in the case of high relative humidity and submerged condition that once concrete specimens are subjected to these conditions: there is a reactivation of curing and hydration process which leads to low porosity and connectivity of concrete pores making it harder for oxygen to diffuse. The findings are quantified in terms of practical field variables such as cover depth and water/cement ratio. This deep experimental investigation involving a variety of material and environmental variables under a wide spectrum of boundary conditions will help in better understanding and will open several significant future prospects of research in the modeling of corrosion under limited oxygen availability. (c) 2009 Elsevier Ltd. All rights reserved.