How to Control Early Shrinkage of Concrete?

Early shrinkage of concrete occurs within 1 to 7 days after pouring, including plastic shrinkage, drying shrinkage, autogenous shrinkage and thermal shrinkage. It tends to cause surface cracks, which will impair the impermeability, durability and even load-bearing capacity of concrete structures.

To prevent cracking effectively, comprehensive control shall be implemented in four key aspects: raw material selection, mix proportion design, construction technology and on-site curing.

1. Raw Materials: Select low-heat cement and limit cement dosage. Use well-graded aggregates, and add high-performance water reducers, retarders and expansion agents. Mineral admixtures such as fly ash and slag powder are also applied to reduce shrinkage fundamentally.

2. Mix Proportion: Optimize water-binder ratio, sand ratio and unit water consumption. While ensuring workability, we minimize concrete shrinkage.

3. Construction Technology: Adopt layered pouring and standard vibration. Control the placing temperature according to ambient conditions. Secondary finishing shall be conducted before initial set to close surface micro-cracks.

4. Curing Management: Timely and sufficient moist curing is required. Follow specifications on curing duration, temperature difference between internal and external concrete, and formwork removal rules.

For projects demanding high crack resistance and ductility, Steel Fibers and Synthetic Fibers (Monofilament Polypropylene Fibers, UHMWPE fibers, etc.) deliver outstanding reinforcement effects. Fibers form a three-dimensional network inside concrete. The fiber bridging effect restricts the initiation and propagation of micro-cracks, greatly improving the resistance to early shrinkage cracking. This solution is widely used in ECC, bridges, floor slabs, municipal works and special structural projects.

In conclusion, controlling concrete early shrinkage requires full-process management. The combination of traditional construction standards and fiber reinforcement technology can fully secure structural stability and long-term service life.