A statistical analysis of the factors which contribute to the corrosion of steel in Portland cement and silica fume concrete

The corrosion of embedded reinforcement has been measured in two series of concrete samples made with and without condensed silica fume (CSF) as a partial replacement for the cement. Three different curing regimes were used and samples were tested at three different ages. Measurements of carbonation, electrical conductivity, strength, lime content and chloride, oxygen and water vapour transport were carried out on matching samples. The results have been analysed using analysis of variance and regression to show which aspects of the materials and methods used to make the samples and which of the measured properties had significant effects on the corrosion. The way in which these effects were modified by the presence of the csf was also analysed. The statistical analysis showed that while the corrosion rate was affected by the water/cement ratio and the curing for all samples the use of CSF significantly increased the sensitivity to poor curing. Also while electrical conductivity and chloride transport were good predictors for corrosion in all of the tests the relative significance of the different predictors was very different for the CSF mixes.