Coupled effect of ambient high relative humidity and varying temperature marine environment on corrosion of reinforced concrete

Chloride induced corrosion under coupled environmental effects of high humidity and high temperature often found in gulf marine environment is a very serious threat for durability of reinforced concrete structures. There exist different schools of thought between various researchers and the data in high relative humidity and high temperature range is also limited. This has been investigated by laboratory controlled experimentation under three different temperature conditions (30,40 and 50 degrees C) and 85% R.N. A non-uniform and non-linear corrosion reaction was observed even after the breaking of passive layer. Furthermore, a decrease in corrosion potential and corrosion mass loss at 50 degrees C in comparison to 40 degrees C temperature conditions was seen. This may be due to the reduction of oxygen solubility in the pore solution at high temperature and blockage of concrete pores at high relative humidity. Thus, producing a reversing trend in corrosion mass loss as a function of chloride concentration at high temperature condition of 50 degrees C and high relative humidity of 85%. It is expected that a stable oxide layer may have developed under limiting oxygen controlled corrosion reaction. This can form basis for the development of a new technique to passivate steel bar embedded in chloride contaminated concrete. The paper also presents qualitative analysis of the microstructure of corrosion products under coupled varying temperature-chloride conditions and identifies the dividing line and turning point chloride concentration. (C) 2011 Elsevier Ltd. All rights reserved.