On attack product and corrosion mechanism of hydraulic concrete after long - Term exposure to natural environment on Western China

A site investigation was made on one deteriorated concrete with 6 years age, and this concrete component was located in one tunnel of one concrete dam in Western China. Some samples were taken from the attacked concrete and were analyzed with XRD, SEM - EDAX and Laser Raman Spectroscopy methods. As a result, it is shown that a mushy mixture consisting of thaumasite, ettringite, gypsum and calcite occurs in the residual concrete exposed to low temperature, high humidity, sulfate and carbonate for a long time. It is validated that the thaumasite form of sulfate attack may occur in hydraulic concrete structures in Western China. In addition, the corrosion mechanism is also discussed.