Abstract:

In order to address the significant degradation of concrete durability caused by long-term external sulfate and carbonate corrosion under dry-wet cycle conditions. This article investigates the erosion and migration patterns of sulfate and carbonate ions inside concrete under dry-wet cycling conditions. Firstly, the damage mechanism of the two ions on concrete erosion was analyzed and compared through the chemical reaction process of ion erosion on concrete and scanning electron microscope (SEM) experiments. Then, the transmission and exchange laws of sulfate ions and carbonate ions at the interface between the concrete surface and the outside world were analyzed by referencing the room model.  The results indicate that, 1) Within 180 days, ion erosion mainly occurs within the range of 0-20 mm on the concrete surface, and the predicted value of the room model deviates from the actual value by about 0.75. 2) The depth of concrete erosion is positively correlated with the water cement ratio, and the room model can predict the degree of concrete erosion. 3) The failure of concrete can be explained from the perspective of the expansion pressure caused by the chemical reaction products of sulfates and carbonates.

Key words: dry-wet cycle, carbonate ion, sulfate ion, concrete