Sulfate Attack on Concrete in an Inland Salt Lake Environment

Several cracks were found on the surface of the concrete foundations that support the steel towers of the Luohe -Huaiyang high-voltage electricity transmission line that is 20 years old and situated in an inland salt lake environment in North China. To analyze the deterioration mechanism that led to this condition, field investigations were carried out and several tests were conducted on the soil and the affected concrete, including XRD (X-ray diffraction), electric probe analysis, and chemical analysis. The results show that the concentration of sulfates is very high (0.39% wt.-0.67%wt.) in both the surrounding soil and the material around the coarse aggregates inside the concrete. Hence, sulfate attack could be one of the main causes of concrete deterioration. The percentage of sulfates in the surface layer of the concrete was higher than that in the inner layers of the concrete. The sulfates penetrate into the concrete and react with the hydrates of cement to form ettringite (AFt), which leads to increase in the volume and cracking of the concrete.