How to Repair Prefabricated Beams in Houses

The repair of prefabricated beams in houses requires targeted measures based on the type of defect. Here are some common repair methods:

I. Surface Defect Repair

1. Pitted Surface: Small pits appear on the surface due to inadequate formwork tightness or insufficient vibration. Before repair, clean the surface dust and evenly apply cement slurry or special repair materials to ensure dense coverage of the defective area.
2. Exposed Reinforcement: Reinforcement is exposed on the concrete surface. First, remove the loose concrete around the reinforcement, clean the rust with a wire brush, apply anti-rust coating, and then fill the gap with epoxy mortar or high-strength concrete, restoring the thickness of the protective layer.
3. Honeycombing/Holes:
   • Small Honeycombing: After rinsing the surface with pressurized water, fill with cement mortar or fine aggregate concrete and compact in layers until dense.
   • Large Holes: Remove the weak layer to solid concrete, support formwork, pour concrete with a higher strength grade, and cure to the design strength.
4. Edge and Corner Damage: When the right-angle edges are damaged, clean the damaged area and repair with cement mortar or epoxy putty, smooth the surface, and cover with a damp cloth for curing.

II. Crack Repair

1. Small Cracks (superficial layer): Apply special adhesive (such as HQG-4# Huaqian Adhesive) or self-mixed adhesive (100 kg adhesive + 10 kg cement) 2-3 times to ensure the adhesive penetrates into the crack.
2. Large Cracks (deep and wide):
   • Chisel the concrete on both sides of the crack to a solid layer and clean the debris;
   • Fill with rapid-repair mortar (formula: 400 kg cement + 600 kg fine sand + 15-20 kg adhesive powder + 155-165 kg water) and compact in layers;
   • If the crack is complex or involves structural safety, it is recommended to contact a professional construction team for handling.
3. Prestressed Beam Damage (such as prestress loss or structural cracking):
   • Release the original prestress (mechanical cutting of steel strands or hydraulic unloading);
   • Reinforce the damaged area with epoxy concrete or high-strength concrete to ensure the bonding strength between the new and old materials;
   • After the reinforcing material reaches the strength, re-tension, strictly controlling the tensioning force and elongation.

III. Air Hole Repair

1. Small Air Holes (pinhole-shaped): Apply thick cement slurry to evenly cover the air holes.
2. Large Air Holes: After removing the loose parts, fill with cement mortar (cement + sand + water), smooth the surface with a trowel, and cover with a damp cloth or plastic film for curing after repair to avoid rapid drying and cracking.

Precautions: Before repair, thoroughly clean the defective surface (such as oil stains and dust) and strictly prepare materials according to the proportions; if the defect is complex or the repair is difficult, it is recommended to contact a professional team for handling.