Damage Evolution of Concrete Exposed to Sulfate Attack Under Drying-Wetting Cycles

摘要

The damage evolution of concrete subjected to drying-wetting cycles in different concentration of sodium sulfatesolution was investigated based on micro and macro-observations. Through the experiment, weight loss, compressivestrength loss and the damage layer thickness of concrete were measured after different drying-wetting cycles. The mechanicalproperties degradation in the damage layer of concrete was also analyzed. Furthermore, the scanning electron microscopyand X-ray diffraction were used to investigate the corrosion products of concrete, and the damage mechanismwas also investigated by the modern microanalysis techniques. The test results show that the deterioration degree ofphysical properties of concrete specimens increases with increasing concentration. Weight loss of specimens caused bysulfate attack is not obvious compared with the other evaluation index. When the damage layer thickness of concrete isthicker as well as the ultrasonic speed is lower, indicating that the deterioration degree of concrete increases, and the compressivestrength loss in damage layer is serious. It was also found that the compressive loss of concrete is correspondwith the observations for the damage layer thickness. Additionally, the main corrosion products of concrete in sulfate solutionssubjected to drying-wetting cycles were confirmed to be ettringite and gypsum, and the quantity of corrosionproducts formed is proportional to the concentration of the solution.