The Importance of Initial Maintenance Time in Controlling Early Contraction

For normal concrete not mixed with admixture, the early shrinkage is minimal, and the early watering and curing primarily facilitate cement hydration, ensuring the development of concrete strength. Therefore, according to the quality acceptance specification for concrete structure engineering construction in our country, the initial curing time for concrete is within 12 hours after pouring.

2. Related experiments have shown that for modern commercial concrete mixed with a large amount of water-reducing agent, there is a sharp increase in shrinkage within 8 hours after initial setting. In actual engineering projects, the appearance of cracks in large-volume slabs mainly occurs within a few hours after the concrete starts to set. Therefore, mastering the timing of initial maintenance is crucial for controlling early shrinkage cracks in commercial concrete. Continuing to wait 12 hours after pouring before watering for maintenance would lose control over the timing of early shrinkage crack formation and would be ineffective in controlling early shrinkage cracks. However, most construction units still adhere to traditional maintenance practices and have not yet adapted to the characteristics of modern commercial concrete, i.e., implementing reasonable maintenance measures immediately after initial setting (before surface water loss) to reduce shrinkage and cracking.