The specification of concrete curing time depends on concrete strength grade, ambient temperature and other factors, which can generally be divided into the following stages: 1. Initial curing period: After concrete pouring, the surface should be covered with moisturizing materials and kept moist for 3-7 days. 2. Mid-term curing period: After the initial curing period, the coverage area of moisturizing materials should be gradually reduced to gradually expose the concrete surface, and the time is generally 7- 14 days. 3. Post-curing period: After the mid-curing period, the concrete reaches a certain strength, which can gradually reduce the coverage area of moisturizing materials, but it still needs to be kept moist 14-28 days. 4. Long-term curing period: After the concrete reaches the design strength, it should be kept wet for more than 28 days. It should be noted that the curing time should be adjusted according to the specific situation, such as environmental temperature, humidity, wind speed and other factors will affect the curing time of concrete. At the same time, the concrete surface should be protected from external impact or vibration during curing, so as not to affect the strength and durability of concrete.