Strength Development of Concrete Exposed in Winter

The relationship of the strength of standard laboratory-cured cylinders to the strength of concrete in columns and slabs and to field-cured cylinders exposed under winter conditions have been reported. The columns, slabs, and about half of the cylinders were left at an outdoor exposure site after an initial 3-day curing at 50 ± 10°F (10 ± 6°C). The remaining cylinders were standard cured. Cores were taken from the columns and slabs at 3, 14, 28, 120, and 355 days for testing in compression. The test results show that concrete initially cured for 3 days at about 50°F (10°C) and about 75% relative humidity and then exposed to below freezing temperatures continues to gain strength. The rate of strength gain of the field-cured concrete shows a marked increase after the ambient air temperature exceeds 50°F (10°C). At the age of about 1 yr, the compressive strengths of the field-cured generally exceeded the standard strength.