Curing time and behaviour of high-performance concrete

Abstract

Because of its susceptibility to self-desiccation, high-performence concrete requires additional curing: generally a 7-day wet curing period is specified which is not an easy task to perform, especially in the field. The purpose of this study was to determine whether the 7 days' wet curing required by the Ministry of Transportation of Ontario for all high-performance concrete structures is necessary to ensure optimum durability. Ordinary Portland cement concrete and two high-performance concretes (one with slag and one with fly ash) were tested. The concrete specimens were cast in a heated enclosure and covered with wet burlap and plastic. They were demoulded after 24 h. Thereafter, one-third of the specimens were wet cured for an additional 24 h, one-third for an additional 2 days and the final third for an additional 6 days; giving total wet curing periods of 2, 3 and 7 days respectively. After 14 days, the enclosure was dismantled and the specimens were exposed to the outdoor ambient conditions and covered with de-icing salts during the winter months. None of the data obtained over the subsequent 2 years for the internal shrinkage strain, the temperature or moisture content, shows any consistent trend with curing period.