Parameters affecting thaumasite formation in limestone cement mortar

Abstract

Abstract Concrete made from limestone cement may exhibit a lack of durability due to the formation of thaumasite. This work deals with the factors affecting thaumasite formation in cement mortars and particularly the limestone content, the curing conditions and the type of sand used. Three types of cement were examined: (i) OPC, (ii) Portland limestone cement containing 15% w/w limestone and (iii) Portland limestone cement containing 30% w/w limestone. Mortar specimens were prepared using calcareous and siliceous sand. The specimens were immersed in a 1.8% MgSO 4 solution and cured at: (i) 5 °C and (ii) 25 °C. The formation of thaumasite was checked and confirmed by XRD and TGA. In addition visual inspection, strength tests and ultrasonic pulse velocity measurements were carried out for several months. It is concluded that mortars containing limestone, either as sand or as a main constituent of the cement, suffer from the thaumasite form of sulfate attack at low temperature. At room temperature, no sulfate attack was observed after a year of exposure.