What to Do If the Prefabricated Floor Slab is Blocked

The treatment plan for a blocked prefabricated floor slab should be selected based on the size of the opening, and it must be carried out by professionals to ensure structural safety. The specific treatment methods are as follows:

I. Classification and Treatment Based on Opening Size

1. Small Openings Within 300 mm

   • If the cut reinforcement does not exceed 5% of the original reinforcement, the opening can be directly sealed without additional reinforcement.
   • If the cut reinforcement exceeds 5%,粘钢 (steel-bonded) or carbon fiber reinforcement techniques should be used, with the reinforcement area needing to be at least 1.2 times the cross-sectional area of the cut reinforcement to restore structural bearing capacity.

2. Medium Openings Between 300-1000 mm

   • Compensation reinforcement or additional edge beams are required. The specific steps are:
     • Remove the concrete around the opening to expose the original reinforcement, and clean the surface rust and impurities;
     • Use new reinforcement to lap (with lap length conforming to specifications) or weld with the original reinforcement to form a reinforced frame;
     • After formwork setup, pour C25-C30 grade concrete, with a curing period of no less than 14 days.

3. Large Openings Exceeding 1000 mm

   • It is necessary to add cast-in-place concrete or profiled steel edge beams to change the load path. If there is a beam at the edge of the opening, part of the beam should be chiseled away and new support notches should be chiseled; the new support beam should be reliably connected to the original structural beam through reinforcement planting, welding, etc., and then the cast-in-place slab should be constructed.

II. Key Construction Considerations

• Opening Method: Directly striking the prefabricated slab is strictly prohibited. A concrete cutting machine or core drilling machine should be used for precise opening to reduce secondary damage to the structure.
• Concrete Requirements: Before sealing, the opening should be thoroughly cleaned, and a sturdy formwork should be set up; during pouring, a multi-stage vibration process should be adopted, using fine aggregate concrete with a micro-expansion agent to ensure the surface is flush with the slab surface, and covered with plastic film for curing.
• Waterproofing Treatment: After the concrete hardens, a leak-stopping compound and two coats of waterproof coating should be applied around the opening to prevent leakage.

III. Special Emphasis
Such renovations involve the safety of the main structure of the building, and must be entrusted to a qualified professional reinforcement company or a certified structural engineer for design and construction. Unauthorized operation may lead to serious consequences such as structural instability and collapse, and may also violate building regulations. Before construction, it is necessary to report to the property management or relevant departments to ensure the compliance of the plan.