Rate of the thaumasite form of sulfate attack under laboratory conditions

In order to give confidence to those responsible for the management of infrastructure, it is necessary to investigate the structural effects of the thaumasite form of sulfate attack (TSA) on buildings and structures. Whereas TSA is less common than other forms of structural concrete deterioration, its consequences can be quite serious. To investigate TSA deterioration of concrete within a reasonable time scale, it is generally necessary to accelerate TSA in the laboratory. Using such an accelerated testing procedure, this paper is concerned with predicting the rate of TSA depending on varying mix designs and aggressive solutions. A methodology was developed to estimate the annual deterioration rate of TSA. It was shown that a combined carbonate and sulfate solution is less aggressive than a pure sulfate solution, and that deterioration rates of up to 1.8 mm/year are possible in commonly used concrete.