Treatment of Gaps in Prefabricated House Slabs

The treatment of gaps in the middle of prefabricated house slabs requires different measures depending on the size of the gaps.

Treatment of Small Gaps

If there are relatively few gaps in the middle of the prefabricated house slabs, and the gaps are small, and there is no liquid flowing on the floor, no repair is necessary. This is because such small cracks have little impact on the structural safety of the house and do not pose a substantial threat to the overall stability and safety of the house. Therefore, no special repair operations are required.

Treatment of Large Gaps

• Repair Steps: First, chisel open the slab joints of the cracks, and chisel away 5 centimeters from each side of the surface layer to make the joint surface slope. This is done to increase the contact area between the repair material and the prefabricated slab and improve the firmness of the bond. At the same time, appropriately roughen the surface of the prefabricated floor slab and the slab sides, and clean off the surface dust and debris to ensure that the repair material can adhere better. Then, brush a layer of pure cement mortar inside the slab joints, with a water-cement ratio controlled between 0.4 and 0.5. Immediately pour and tamp fine aggregate concrete. Pour and tamp for the first time to half the depth of the slab joints. After the fine aggregate concrete absorbs water for a moment, perform the second pouring and tamping until it is compacted and leveled 1 centimeter from the slab surface. After the repair is completed, it should be cured for at least 2 - 3 days, during which no one is allowed to step on it to ensure that the repair material can fully solidify and reach the designed strength.
• Other Requirements: The gaps between the prefabricated slabs must be properly treated. Before treatment, clean the debris inside the slab joints first, and then pour and vibrate cement mortar to make it dense, ensuring that the cement mortar can fully fill the gaps without any voids. If the gaps are large, use concrete for on-site pouring and solidification before curing. It is forbidden to fill the gaps with bricks because bricks have different materials and properties from prefabricated slabs. Filling with bricks cannot guarantee the integrity and stability of the gap area, and new problems may arise during subsequent use.

In addition, when installing prefabricated slabs, a gap of 20 - 40 millimeters should be left between two slabs. This is to provide a certain space for the deformation of the prefabricated slabs under temperature changes, stress, and other conditions, and to avoid the generation of cracks due to mutual extrusion.