Methods for Reinforcing Bars in the Roof of Prefabricated Houses

There are several methods for reinforcing bars in the roof of prefabricated houses, and the specific operation should select the appropriate method according to the actual situation and follow relevant specifications:

I. Adding Steel Mesh in Slab Joint Treatment When the width of the slab joint between prefabricated slabs exceeds 50mm, steel mesh should be added to the joint to enhance the connection strength. During the specific operation, first clean the debris and dust in the slab joint to ensure a clean contact surface; then embed the steel mesh (usually made of cold-drawn low-carbon steel wire with a diameter of 4-6mm) into the joint, with the mesh size covering at least 100mm on both sides of the joint; finally, pour fine aggregate concrete with a strength not lower than C20, vibrate it densely, and cure it to the design strength. If the slab joint width exceeds 120mm, it is necessary to switch to a reinforced skeleton cast-in-place slab strip treatment: embed anchor bars on both sides of the slab joint, bind longitudinal bars with a diameter not less than 8mm and stirrups with a diameter of 6mm to form a skeleton, and then pour concrete to form an integral structure.

II. Laying Steel Mesh During Pouring of Composite Layer Adding a reinforced concrete composite layer on the surface of the prefabricated slab can significantly improve the overall stiffness. The construction steps are as follows:

1. Base Treatment: Use a high-pressure water gun or wire brush to remove dust and oil stains from the surface of the prefabricated slab to ensure a firm bond between the new and old concrete;
2. Steel Mesh Laying: Use cold-rolled ribbed steel bars with a diameter of 6mm, bind them into a mesh at intervals of 200mm×200mm, with a lap length of the mesh not less than 150mm, and fix the ends to the anchor bars embedded in the prefabricated slab with iron wire;
3. Concrete Pouring: Use fine aggregate concrete with a strength not lower than C25, control the thickness between 50-80mm, vibrate it densely with a flat vibrator during pouring, smooth the surface with a wooden trowel and roughen it, and the curing period should be no less than 14 days.

III. Section Enlargement Reinforcement Method When the bearing capacity of the prefabricated slab is insufficient, the section enlargement method can be used for reinforcement. Add a reinforced concrete layer not less than 40mm thick on the slab surface or bottom:

• Slab Surface Reinforcement: Chisel off the protective layer on the slab surface to expose the steel bars, clean them, bind a two-way steel mesh with a diameter of 8-12mm (spacing 150-200mm), connect it to the original steel bars by welding or binding, and then pour concrete;
• Slab Bottom Reinforcement: Use formwork cast-in-place method to add a steel mesh at the slab bottom and connect it to the original structure through chemical anchors or planted bars. It should be noted that this method requires strict calculation of the impact of the additional load on the original structure and design verification by a professional institution.

Construction Points: All steel bar connections must meet the requirements for lap length and anchor length in the "Code for Design of Concrete Structures"; after concrete pouring, it should be covered and moisturized for curing to avoid early cracking; when involving structural modification, relevant approval procedures should be completed in advance and the construction should be carried out by a qualified unit.