Cracking of Prefabricated Slabs in Zhangzhou Houses

Different treatment measures should be taken for cracking of prefabricated slabs in Zhangzhou houses based on the crack conditions.

In Zhangzhou, homeowners in communities such as Tefang Jinxiubihu A District and Changtai District Poly Daguo Jing have reported cracking issues with the prefabricated slabs in their houses, involving multiple locations such as living rooms, bedrooms, and kitchens. Cracking of prefabricated slabs may be caused by factors such as material aging, temperature changes, improper construction, or house settlement, and targeted treatment methods should be adopted according to the severity of the cracks.

If there are few cracks, the gaps are small, and there is no leakage, repairs can be temporarily postponed. Such cracks are usually shrinkage cracks or temperature cracks, which have a relatively small impact on the structural safety of the house. However, it is necessary to regularly observe whether the cracks expand. If there is an increase in width, an increase in number, or leakage, timely treatment is required.

If the cracks are large or leakage occurs, immediate repairs are necessary. The specific steps are as follows:

1. Crack treatment: Chisel open the crack in the slab joint, chisel away 5 centimeters of the surface layer on both sides to make the joint surface slope-shaped, and appropriately chisel the surface of the prefabricated floor slab and the slab side to enhance the bonding force between the new and old concrete.
2. Clean the base layer: Use a brush or high-pressure air gun to clean the chiseled surface to ensure there is no dust, oil, or other impurities.
3. Apply cement mortar: Apply a layer of pure cement mortar inside the slab joint, with a water-cement ratio controlled between 0.4 and 0.5, to seal the cracks and enhance the bonding.
4. Pour and tamp fine aggregate concrete: Pour and tamp for the first time to half the depth of the slab joint. After the fine aggregate concrete absorbs water for a moment, pour and tamp for the second time until it is compacted and leveled 1 centimeter from the slab surface.
5. Curing: After the repair is completed, cure for at least 2-3 days. During this period, stepping on or applying loads is strictly prohibited to ensure the full hardening of the concrete. Precautions: When dealing with cracks, avoid drilling holes in the prefabricated slabs to prevent damaging the load-bearing structure of the floor slab. If a ceiling is required, the hanging rods should be installed in the joints between two prefabricated slabs to ensure construction safety.

If the cracks seriously affect the structural safety, reinforcement methods can be adopted. For example, the crack grouting reinforcement method involves injecting materials such as epoxy resin under high pressure to fill the cracks and restore the structural integrity. Or carbon fiber reinforcement can be used, where carbon fiber cloth is pasted on the surface of the cracks to improve the crack resistance of the floor slab. The reinforcement plan should be evaluated and implemented by a professional institution.