Study on the deterioration mechanism of cement-based materials in acid water containing aggressive carbon dioxide

The deterioration mechanism of cement-based materials in mixed solution of corrosive CO2 and H+ was experimentally investigated. A carbonation model with the moving boundary was proposed to predict the corrosion depth of cement paste in the mixed solution of aggressive CO2 and H+ in this paper. A test apparatus and method for the preparation of mixed solution of aggressive CO2 and H+ was designed and manufactured. The corrosion tests of cement paste and concrete under different corrosion condition were implemented and the corrosion depth were obtained. The microscopic test methods were also applied to study the corrosion mechanism of cement-based materials. In addition, a carbonation model with the moving boundary was proposed to simulate the corrosion process. Results indicate that both the single and dual corrosion of aggressive CO2 and H+ solution have an obvious damage on the quality of cement paste and concrete. The damage of dual corrosion of aggressive CO2 and H+ on the specimens are greater than that of single aggressive CO2 solution or the strong acidity. The corrosion region can be divided into gel layer, carbonated layer and transition layer. The carbonation model with a moving boundary can be used satisfactorily to predict the corrosion process of cement paste. This paper provides experimental and numerical methods for the future investigations on the durability of underground structures in acid water containing aggressive carbon dioxide. (C) 2020 Elsevier Ltd. All rights reserved.