PHYSICAL AND CHEMICAL SIMULATION OF THE THAUMASITE FORM OF SULFATE ATTACK ON CONCRETE

The transformation of physical and chemical performance was studied in the thaumasite form of sulfate attack (TSA) process on cement mortars, A physical and chemical simulation of TSA process was established, and the mechanism of thaumasite formation is further discussed. The visual appearance, linear deformation, mass loss and strength were tested at different storage times, and then the analysis towards the physical transformation in TSA process was carried on. X-ray diffractometer, Fourier transform infrared spectrometer and other modern testing technologies were used to analyze the chemical transformation in the TSA process. The macroscopical peculiarity due to the TSA process included corrosions from surface to inside. Gray mud Without any strength appeared on the surface, and strength loss inside mortars. When the corrosion time arrived at 450(th) day, the FTIR results of mortars' surface showed the characteristic peak value Of SiO6 (501cm(-1)), and confirm the thaumasite formation. The physical process of TSA could be disparted to 3 periods: delitescence, expansion and crack period and intenerated and disaggregating period; the chemical process of TSA could be disparted to 4 periods: ionic migration period, ettringite formation period, gypsum formation period and thaumasite formation period.