Thaumasite formation in sugary solutions: Effect of temperature and sucrose concentration

Thaumasite formation in cementitious environments is attributed to sulphate attack (internal or external). Thaumasite is characterized by the presence of octahedrally coordinated silicon, but is formed from the silicate phases of cement, (mainly C–S–H gel), whose silicon atoms are tetrahedrally coordinated. Thaumasite formation is favoured at low temperatures and from recent studies sugar solutions increases calcium solubility and also increases the velocity of formation of thaumasite. The aim of the present study is to explore the effect of temperature (5 °C and 25 °C) and sucrose concentration (5%; 10% and 20% wt) on thaumasite formation from lime and sodium carbonate, sulphate, silicate sugary solutions. Precipitates formed different ages were characterized by XRD and FTIR. At 5 °C larger proportions of thaumasite were formed in 10% sucrose however at 25 °C, the 20% sugary solution generates more thaumasite at shorter times.