ABSTRACT
The most significant finding of this study was the beneficial effect that derived from precuring the concrete specimens, (Portland and slag cements), in air at 20°C and 65% RH prior to storage in sulphate solution. Even a ‘token’ storage in air for a short time, probably for only several hours, following the demoulding of the concrete cubes at 24 hours, was sufficient air-curing to provide an improved sulphate resistance compared to the water-cured specimens. The performance of those specimens placed directly into water after demoulding, particularly for the high C3A OPC concrete, was considerably reduced. This can be attributed to the fact that no carbonated layer had been allowed to form even though the optimum early strength development and concrete design strength had been achieved by water-curing.
