ABSTRACT
Abstract In the thaumasite form of sulphate attack, the main mechanism of deterioration is the breakdown of the calcium silicate hydrate phases in hardened cement pastes in the presence of sulphate and carbonate ions, followed by the formation of the mineral thaumasite. The following paper describes two large programmes of work in which this form of deterioration was reproduced in laboratory-prepared concretes and mortars containing two different sources of limestone. The effect of mix composition on the degree of reactivity is discussed along with the effect of environmental conditions such as temperature and different sulphate sources. Keywords: Blended cements, concrete, limestone aggregates, limestone filler cements, Portland cements, sulphate attack, thaumasite
In the last few years, the Building Research Establishment (BRE) has been involved with three case studies where concrete foundations have deteriorated as a result of the thaumasite form of sulphate attack [1] [2] [3]. The conditions favoured for thaumasite (CaSi03.CaC03.CaS04.15H20) formation are cold wet environments, a source of calcium silicate, and a readily available supply of carbonate and sulphate ions.
