Precast piles can be constructed within 3 to 7 days after steam curing. Generally, it is required to reach 100% of the design strength before use. But there is no requirement for how many days. Because general natural curing takes 28 days, steam curing or adding early strength agent to concrete can reach the design strength 3-7 days in advance and can be used. In order to speed up the turnover of the model, the concrete precast factory should take early strength measures. Different early strength measures will lead to different days for members to reach the design strength. So there is no uniform regulation.