Two sets of experiments simulating the curing conditions of concrete caisson constructions in the Arctic were carried out at Sherbrooke University, Province of Quebec, Canada, and at Nanisivik, in the extreme north of Baffin Island, Canada (73° north). More than 500 concrete specimens were tested for various ages and initial curing periods. After they were cast, the concrete specimens were initially cured at about 4°C (39°F) for 3 to 15 h and then immersed in seawater at 0°C (32°F) until testing. Their compressive strengths at different ages, up to one year, and Young's modulus at 28 days were compared with those of specimens of the same concrete and same age cured under room temperature.
These two sets of experiments have shown that if 9 h of initial curing at about 4°C (39°F) is allowed for the concrete before immersion in seawater at 0°C (32°F), the design compressive strength of the concrete can be achieved at 56 days. The rate of development of compressive strength during the first two weeks is slow because of the low temperature of the curing environment.
The temperature of the fresh concrete and its water/cement ratio are the two most important parameters that determine the early strength of the concrete.