Effect of carbonic acid water on the degradation of Portland cement paste: Corrosion process and kinetics

• Changes of Portland cement paste in carbonic acid water were followed.
• Carbonic acid water corrosion process of Portland cement paste was described.
• A carbonic acid water corrosion model of Portland cement paste was proposed.
• A corrosion kinetics was theoretical deduced and fitted with experimental data.

Underground concrete structures usually suffer from carbonic acid water corrosion, thus evaluation and prediction of the carbonic acid water corrosion are very important for cement-based materials. Portland cement pastes were immersed into a renewal carbonic acid water, then the corrosion process was followed in this paper. The results show that no obvious corrosion was observed in the first 7 days, while significant corrosion was observed after 28 days corrosion. The corroded zone can be divided into three regions according to the Ca/Si molar ratio of the cross section, where dissolution of CH, carbonation and dissolution of carbonates, and multi-decalcification of hydration products occurred gradually from the internal to the external. Based on the experimental data, a carbonic acid water corrosion model of Portland cement paste was proposed, then the corrosion kinetics, which can be used to predict the carbonic acid water corrosion of Portland cement paste, was theoretically deduced and fitted using the experimental data.