Characterization and Mathematical Modeling of Chloride Diffusion in Lagos Coastal Waters

Reports and news on failure due to corrosion degradation of structures in aggressive environments are common occurrences in literature nowadays. This paper presents deterioration pattern of concrete structures in a coastal environment and effects chloride concentration on the steel reinforcements in concrete as a way towards failure control: water samples were collected from coastal environments (Tin Can Island and Bar Beach, Lagos, Nigeria). Laboratory analyses were carried out to determine the chloride contents and values obtained for the chloride concentrations were used to prepare different concentrations of chloride solutions to be used as aggressive curing environments. The test blocks were connected in parallel to a D.C rectifier set at 10 V to accentuate the rate of corrosion. A Half-Cell potential apparatus was used to determine the corrosion potential at intervals of 4 days for a period of 28 days after the initial 28 days of curing. A simple statistical model that relates chloride concentrations to the strength of the concretes was developed and tested. The study revealed that chloride concentration has significant effect on reinforcement. Rebar in 24878.80 mg/L curing tank was the most affected by corrosion with potential reading of 466.50 mV and the rebar in this block was not able to sustain any tensile load. The model developed described the strength of the concretes with correlation coefficient R 2 higher than 0.950 ( R 2 > 0.950).