Effect of CO2 partial pressure and temperature on degradation kinetics of cement paste in CO2-rich water

In karst areas, the groundwater typically exhibits high levels of carbon dioxide (CO₂-rich water), which leads to the calcium leaching of underground concrete structures. The deterioration of concrete cover can cause the corrosion of the steel bars, resulting in a serious threat to the durability of the structures. In this paper, the degradation behaviors and microstructure development of cement paste under different CO₂ partial pressures (0.1, 0.4, 0.8 MPa) and temperatures (5 °C, 25 °C, 50 °C) of CO₂-rich water were studied, and the degradation kinetics were discussed. The results indicate that the reaction of the cement paste is prone to occur in CO₂-rich water, with an activation energy of 6.46 kJ/mol. The degradation process results from the combined effects of carbonation and calcium leaching. Both increased CO₂ partial pressure and temperature accelerate degradation, however, and the sensitivity of temperature is significantly higher than pressure. Based on this, we establish a prediction model of degradation depth, which is applied to the cement paste with intact degradation layer in low flow rate of CO₂-rich water.