【Haichuan Civil Engineering】Concrete Curing: Is it before final setting or after final setting?
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According to Article 8.5.1 of the "Construction Specifications for Concrete Structure Engineering" (GB50666-2011), moisturizing and curing should be carried out in a timely manner after concrete is poured. Moisturizing and curing can adopt methods such as sprinkling, covering, and spraying curing agents. The maintenance method should be determined based on factors such as site conditions, ambient temperature and humidity, component characteristics, technical requirements, construction operations, etc. Article 8.5.1 explains that the early plastic shrinkage and drying shrinkage of concrete are large, which can easily cause concrete cracking. Concrete curing is an important measure to replenish moisture or reduce the water loss rate, prevent cracks in concrete, and ensure that various mechanical performance indicators of concrete are achieved. After the initial setting and final setting plastering treatment of concrete, maintenance work should be carried out in time. The time interval between the final setting of concrete and the start of curing should be shortened as much as possible to ensure the humidity required for concrete curing and to control the temperature of the concrete. "Technical Specifications for Waterproofing of Underground Engineering" (GB 50108-2008): Waterproof concrete should be cured immediately after final setting, and the curing time should not be less than 14 days.
According to the specifications, concrete curing is carried out after the final setting of the concrete. Why is waterproof concrete cured after final setting? Because waterproof concrete will form a hydrophobic film after the hydration reaction, it is this hydrophobic film that plays the role of waterproofing and water blocking. Therefore, you must wait for the hydration reaction of the waterproof concrete to be complete before sprinkling water for curing, so as not to destroy this hydrophobic film and ensure that the waterproof concrete plays a waterproof role. There is one thing you must pay attention to when it comes to waterproof concrete: It should be cured immediately after final setting. Because if the curing is not timely, the moisture inside the concrete will evaporate quickly, resulting in incomplete cement hydration. The evaporation of water will cause the capillary network to connect with each other, forming a seepage channel. At the same time, the concrete will shrink and crack, and the impermeability will drop sharply, and even the impermeability will be completely lost.
After the initial setting and final setting plastering treatment of concrete, maintenance work should be carried out in time.