When the daily average temperature is lower than 5 degrees, the hydration reaction of concrete is slow and the strength rises slowly. If you water it, the temperature of concrete will be lower, which is not conducive to strength development. When the average temperature is below 5 degrees, the lowest temperature at night is often below 0 degrees. After the concrete is cured by water spraying, the water film on the concrete surface will freeze, which will cause frost heaving damage to the strength development of concrete.

Concrete members are placed in a curing room filled with saturated steam or a mixture of steam and air to accelerate the hardening of concrete in high temperature and high humidity environment. The curing effect is related to the steam curing system, including: standing time before steam curing, heating and cooling speed, curing temperature, constant temperature curing time, relative humidity and so on. Steam curing room has pit type, vertical kiln type and tunnel kiln type.

Extended data:

During the period of concrete curing, we should focus on strengthening the humidity and temperature control of concrete, minimize the exposure time of surface concrete, and cover the exposed surface of concrete closely (tarpaulin, plastic sheeting, etc.) in time. Can be used to cover) to prevent evaporation of surface moisture.

Before the initial setting of the exposed surface protective layer concrete, the covering should be rolled up and rubbed with a trowel at least twice to make it smooth, and then covered. At this point, attention should be paid to the fact that the covering should not directly contact the concrete surface before the final setting of the concrete.

During steam curing, the temperature should be measured regularly and recorded. The pressure thermometer is arranged in the inner box span, 4m near the beam end and outside the side formwork. Measure the temperature every 2 hours at constant temperature, and every 1 hour at temperature rise and fall to prevent concrete cracks.

After steam curing, water must be sprayed immediately for curing, and the time shall not be less than 7 days. For concrete poured in winter construction, covering curing should be adopted. When the average temperature is lower than 5℃, it should be maintained according to the winter construction method, and the box girder surface should be sprayed with curing agent.

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