How to Reinforce Prefabricated House Slabs

The reinforcement methods for prefabricated house slabs should be selected based on specific issues, with common reinforcement approaches as follows:

I. Reinforcement Methods for Local Issues

1. Reinforcement for Slab Openings
   If the opening is located in the mid-span area of the slab, equal-strength carbon fiber sheets should be adhered to both sides of the hole. Carbon fiber sheets have high tensile strength, effectively compensating for the loss of flexural bearing capacity caused by the opening and reducing the risk of structural deformation. During construction, ensure that the carbon fiber sheets are firmly bonded to the slab base to avoid voids.

2. Reinforcement for Insufficient Bearing Length
   When the bearing length of the prefabricated slab does not meet design requirements, angle steel supports can be added on both sides of the slab joint. The angle steel should be fixed by drilling holes at intervals and installing through bolts, forming a stable support system. This method enhances the restraint at the slab end, preventing slippage or fracture caused by insufficient bearing length.

II. Holistic Reinforcement Methods

1. Grouting Reinforcement Method
   By injecting cement-based grout into walls or foundations, voids are filled, and overall strength is enhanced. This method improves structural stability and seismic performance, particularly suitable for foundation settlement or wall crack repair. During construction, control the grout mix ratio and injection pressure to avoid secondary damage to the original structure.

2. Steel Mesh Reinforcement Method
   Lay a steel mesh (e.g., Φ6@200 bidirectional steel mesh) on the surface of walls or slabs and fix it with anchors or planted rebars. The steel mesh works in conjunction with the original structure, significantly improving overall crack resistance, suitable for seismic reinforcement of old houses. After construction, plaster the steel mesh to prevent corrosion.

3. Steel Plate Bonding Reinforcement Method
   For prefabricated slabs with cracks or deformation, steel plates (typically 4-6mm thick) can be bonded to the surface and fixed with structural adhesive. The steel plates bear part of the load, enhancing structural stiffness, suitable for emergency reinforcement when bearing capacity is insufficient. During construction, ensure no voids between the steel plate and slab and provide corrosion protection.

III. Special Reinforcement for Old House Renovation

1. Structural Safety Assessment
   Before renovation, comprehensively inspect the crack width of prefabricated slabs (repair with grouting or carbon fiber sheets if exceeding 0.3mm) and the corrosion rate of connecting bolts with ring beams (replace if exceeding 30%). Focus on evaluating key indicators such as slab end supports and mid-span deflection.

2. Temporary Support System
   During construction, set up steel pipe supports every 1.2 meters along the length of the prefabricated slab, with critical nodes supported by H-section steel beams (cross-section ≥ 200×200mm). The support system should be calculated for bearing capacity to ensure structural safety during slab removal.

3. Slab Joint and Constructional Column Reinforcement
   After removing the original slab joint filling material, implant Φ6 threaded rebars and pour C30 fine aggregate concrete; add 240×240mm constructional columns at the four corners of the house, with reinforcement of Φ6@200 (stirrups) and Φ8@200 (longitudinal bars), reliably connected to the slab.

4. Construction Sequence Control
   Follow the principle of "middle first, then sides," with daily removal not exceeding 30% of the total slab area. Continuously monitor stress changes in the support system during construction, prohibiting the use of heavy hammers for impact removal to avoid local stress concentration leading to collapse.