The objective of this paper was to reproduce the formation of thaumasite due to the reaction of atmospheric SO2 with hydraulic mortars. The research was carried out on mortars made with ordinary Portland cement (OPC), mineralized white Portland cement, hydraulic lime and a mixture of lime and pozzolana. Mortars underwent sulfation by exposing the samples to 300 PPM SO2 at 25 degreesC and 95% RH for 2 days. Subsequently, half of the sulfated samples were kept for 6 and 12 months in a chamber with 0.3 ppm, SO2 as pollutant (0.501 min(-1) flow gas velocity), 5 degreesC and 95% RH. The other halves of the sulfated samples were kept partially immersed in water at 5 degreesC for 4, 9 and 14 months.