Flat-Roof Eave Secondary Rebar Prefabrication

Flat-roof eave secondary rebar prefabrication is a technique that achieves structural reinforcement or prefabricated component connection through processes such as drilling, hole cleaning, adhesive injection, and rebar insertion. It is suitable for scenarios such as eave repair, load addition, or anchoring of prefabricated overhanging eave panels.

Core Process and Scope of Application

For secondary structural rebar insertion, holes are drilled in the concrete substrate (hole diameter = rebar diameter + 4-8 mm, hole depth ≥ 15 times the rebar diameter). High-strength epoxy structural adhesive is injected (filling volume ≥ 90% of the hole volume), followed by rebar insertion and curing maintenance (no disturbance within 24 hours at room temperature). This technique is primarily used for reinforcing non-load-bearing structures, such as rooting of constructional columns and anchoring of equipment foundations. In flat-roof eave scenarios, it is commonly used to repair defects such as concrete cracking and rebar displacement, or to add loads such as sunshades. If prefabricated components (e.g., prefabricated overhanging eave panels) are used for the eaves, rebar insertion can achieve reliable anchoring between the prefabricated parts and the existing structure, ensuring overall stability.

Key Construction Control Points

1. Drilling and Hole Cleaning: Adopt the 'three-blow and two-brush' process (air compressor dust blowing → steel brush wall brushing → secondary dust blowing) to thoroughly remove dust from the holes. Dust residue can reduce bond strength by ≥40%.
2. Adhesive Selection: Prioritize the use of modified epoxy resin Class A adhesive (tensile strength up to 30 MPa). For rebar diameters > 22 mm or important structures, such adhesive must be used.
3. Rebar Treatment: The inserted rebar must be derusted, and the anchoring length must meet design requirements. The diameter should preferably not exceed 25 mm (recommended by group standard T/CECS 1847-2025).
4. Curing Maintenance: Cure at room temperature for 24 hours. For every 5°C decrease in temperature, the curing period must be extended by 50%. Protection is required for construction in rainy weather. Adhesive moisture content > 5% can lead to failure.

Quality Inspection and Standard References

After construction, pull-out testing is required. The loading rate should be ≤ 3 kN/s, the holding time ≥ 120 seconds, and a displacement of ≤ 0.1 mm is considered qualified. The number of tests should be ≥ 1% of the rebar insertions of the same specification and not less than 3. Disturbing the rebar after insertion can result in a 60% loss of bond strength, so strict avoidance is necessary. It is recommended to follow the 'Technical Specification for Post-Installed Fastenings in Concrete Structures' JGJ 145-2013 and the 'Design Code for Strengthening Concrete Structures' GB 50367-2013 to ensure process compliance.