1. Introduction: Repair Advantages
Steel fiber concrete (SFC) enhances old building crack repair by integrating cold-drawn or copper-plated steel fibers, boosting tensile strength by 40%-80% and crack resistance by 3-5 times. The 3D random distribution of fibers forms a "micro-reinforcement" network, preventing crack propagation while maintaining compatibility with traditional concrete processes.
2. Pre-construction Assessment
2.1 Crack Diagnosis
- Classify cracks via ultrasonic detection and width gauges:
- Structural cracks (>0.3mm): Require prior reinforcement;
- Non-structural cracks (≤0.3mm): Proceed with direct repair.
- Map crack distribution for targeted material selection.
2.2 Fiber Selection & Mix Design
- Cold-drawn fibers
- Copper-plated fibers
- Dosage: 0.5%-2.0% of concrete volume (15-30kg/m³ for C30), adjusted via slump test (5-10mm reduction per 1% dosage).
3. Core Construction Steps
3.1 Crack Preprocessing
- Chisel 200mm around cracks to 5-10mm depth for rough surface;
- Clean with high-pressure air and acetone, apply epoxy interface agent.
3.2 SFC Mixing & Pouring
- Pouring tips
- Use ≥50mm diameter pump to prevent blockage;
- Pour in ≤150mm layers, vibrate away from fiber clusters.
3.3 Surface & Crack Control
- Trowel before initial set to eliminate plastic shrinkage;
- Add anti-crack mesh for large-span components (e.g., slabs).
4. Curing & Quality Assurance
4.1 Curing Protocols
- Moist-cure with film within 12h, maintain ≥14 days (≥5℃);
- Water spray in humid conditions, sunshade in high temperatures.
4.2 Acceptance Criteria
- Crack width ≤0.1mm (28-day loading test);
- Bond strength ≥1.5MPa (GB 50550-2010);
- Fiber spacing ≤3mm (microscopic inspection).
5. Technical Benefits
6. Conclusion
SFC offers a robust solution for old building crack repair, combining reinforcement, toughening, and crack resistance. Precision in material selection and process control ensures reliable, cost-effective results. Contact us for project-specific SFC solutions and technical support.
Revisions Highlights:
- Removed redundant phrases (e.g., "core advantage lies in" → "forms");
- Shortened sentences (e.g., merged "repair advantages" paragraphs);
- Used industry abbreviations (SFC, RC) for conciseness;
- Standardized metric units and test references;
- Eliminated repetitive technical explanations (e.g., combined mixing steps).