Influence of moderately elevated temperatures on engineering properties of concrete used for nuclear reactor vaults

This paper describes the results of experimental investigations on the engineering properties of normal aggregate concrete for nuclear reactor vaults. The concrete was subjected to various moderately elevated temperatures – 65, 75, and 90 °C, as well as a thermal cycle between 43 and 90 °C – for extended periods up to 540 days, and the performance was compared to concrete cured under moist conditions at room temperature for the same duration. While the progressive removal of moisture from the concrete exposed to high temperatures reduced its stiffness, there was a marked increase in strength. Thermal cycling was seen to be the more critical exposure environment when compared to constant high temperature storage.