Applications of Electron Probe Microanalyzer for Measurement of Cl Concentration Profile in Concrete

Electron probe microanalysis (EPMA) has been applied for the quantitative evaluation of Cl ingress into concrete. In order to obtain quantitative data on Cl concentration, the measurement conditions were discussed statistically in detail and sample measurement conditions were introduced. The absolute concentrations of Cl obtained through EPMA were found to be equivalent with wet analysis and the effect of matrix differences to be negligible. By using the difference in chemical composition between cement paste and aggregate measured by EPMA with a spatial resolution of 100 μm, it was possible to discriminate the paste part in concrete. Since Cl penetrates into concrete through the paste part, the Cl concentration profile obtained by EPMA is useful for the estimation of the apparent Cl diffusion coefficient, Da. The quantified value of Cl concentrations obtained with EPMA were confirmed through comparison with traditional slicing and grinding methods. Based on the measurement results, the Da value was calculated for various concrete mixtures and the results were found to be equivalent with those yielded by conventional methods.