According to the requirements of Code for Construction and Acceptance of Concrete Structure Engineering (GB50204-92), it should be no less than 14 days.

The relevant chapters are as follows:

Section 5 Natural curing of concrete

Article 4.5. 1 The poured concrete shall be covered and watered, and shall meet the following requirements:

A, after concrete pouring 12h should be covered with water;

Second, the water curing time of concrete, for concrete mixed with portland cement, ordinary portland cement or slag portland cement, shall not be less than 7d and shall not be less than14d; For concrete mixed with retarding admixture or with impermeability requirements;

Three, watering times should be able to keep the concrete in a wet state;

Four, concrete curing water should be the same as mixing water.

Note: ① When the average temperature of the day is lower than 5℃, no sprinkling is allowed;

(2) When other kinds of cement are used, the curing of concrete should be determined according to the technical performance of the cement used.

Article 4.5.2 The cured concrete shall be covered with plastic sheets, and all exposed surfaces shall be covered tightly with plastic sheets, and there shall be condensed water in the plastic sheets.

Note: When the concrete surface is inconvenient for watering or curing with plastic sheets, it is advisable to brush a protective layer (such as film curing solution) to prevent the water inside the concrete from evaporating.