Detailed Construction Steps

Step 1: Surface Preparation (The Foundation of Adhesion)

· Cleaning: Remove degraded concrete, oil, and dust using disc grinding or high-pressure water jets. 
· Crack Treatment: Cracks exceeding 5mm shall be grouted with high-strength cement mortar; those between 0.1mm and 5mm require low-pressure chemical adhesive injection followed by grinding, while cracks under 0.1mm should be surface-sealed. 
· Leveling: Repair hollows or honeycombed surfaces with specialized repair putty. Adjust height differences to ensure a smooth substrate. 
· Corner Radiusing: Grind sharp convex corners to a smooth radius (R≥20mm) to prevent stress concentration and fiber breakage.

Step 2: Primer Coating

· Purpose: Primer penetrates the substrate to enhance surface strength and ensure a robust bond between the concrete and the fiber wrap or repair resin.
· Environmental Conditions: Apply only when the temperature is 5°C, humidity is 85%, and concrete moisture content is < 10%.
· Mixing: Use low-speed mechanical mixing for ~3 minutes. Prepare small batches to be consumed within 45–60 minutes to prevent excessive heat and premature curing.
· Application: Apply 1–2 coats via roller or brush at a standard rate of 0.25–0.3 ; highly carbonated concrete may require additional coats. Proceed to the next stage only after the primer is tack-free (typically 24 hours).

Step 3: Leveling & Defect Repair

· Purpose: Ensure a level application surface to prevent air bubbles or bulging between the concrete and the fiber wrap; use to rectify surface irregularities, voids, and height offsets. 
· Application Timing: Apply repair adhesive immediately after the primer is tack-free. If more than 10 days have elapsed, the surface must be sanded before application. 
· Coverage: For honeycombed surfaces, apply a comprehensive coat. Standard consumption is 0.5–1.5 depending on surface conditions. 
· Curing & Refinement: Allow 24 hours for curing before proceeding. If outgassing from the concrete causes bubbles in the adhesive, grind them flush using an angle grinder once cured.

Step 4: Impregnating Resin Application (Base Layer)

· Purpose & Technique: Use resin to bond the fiber wrap to the concrete. Ensure full saturation by rolling the fiber in a single direction with a specialized roller. Use a serrated de-foaming roller to remove trapped air, especially at arches and corners. 
· Mixing & Pot Life: Calculate batch sizes based on the application area to ensure use within the workable time. Mix thoroughly, paying close attention to the bottom and corners of the mixing container. 
· Application Rate: Apply evenly until the fiber is fully saturated; avoid excessive resin. Squeegee out excess resin with specialized tools. Standard consumption is 0.5–0.7 kg/m² per layer, depending on the substrate and fiber specifications.

Step 5. Fiber Wrap Application

· Purpose & Alignment: The goal is structural reinforcement. Fiber orientation must align with the design stress direction. Ensure the fabric is laid flat without wrinkles or kinks. Use specialized rollers to saturate the fabric and eliminate all air bubbles.
· Cutting & Handling: Include overlap dimensions in cuts. Never fold carbon fiber; store pre-cut strips rolled on a core (R≥80mm) to prevent fiber damage. Store unused fabric in a dust-free, dry, and shaded area.
· Bonding Technique:

• Layering: Follow marking lines. For multi-layer applications, apply one layer at a time, allowing each to cure before the next.
• Sequence: When applying multiple strips in one area, start from the center and work outward.
• Corners: Handle external corners carefully to avoid fiber breakage. For internal corners, use a matching-radius rubber roller to press the fabric firmly into the corner, preventing "pull-off" or peeling.
• Rolling: Roll in the fiber direction only; avoid back-and-forth strokes.

· Overlapping & Obstructions:

• Overlap Length: Minimum 100mm in the fiber direction (or 200mm per specific standards). No overlap is required perpendicular to the fiber unless specified (≥30mm).
• Obstructions: Plan cuts in advance around openings or hardware; prepare additional reinforcement for these weakened areas.

· Curing & Protection:

• Protection: Cover with plastic sheeting for at least 24 hours to protect from rain and dust.
• Curing Times: Initial curing takes 1 day at > 20°C, 1–2 days at 10–20°C, and 2 days at < 10°C.
• Loading: Full structural loading requires ≥80% cure. At 20°C, wait 7 days before loading; at 10°C, wait 14 days.

Step 6: Impregnating Resin Topcoat

· Purpose: Provides surface protection or prepares the interface for the next layer of fiber wrap.
· Inspection: Monitor the fabric for lifting, bulging, or peeling from application until curing. Address any defects immediately.
· Defect Remediation:

• Uncured Defects: Use a de-foaming roller to push trapped air out in the direction of the fibers.
• Cured Defects: If bulges have already hardened, drill small vent holes and inject resin using a syringe to fill the void.

Step 7: Surface Finishing

· Purpose: To prevent resin whitening and degradation. Exposure to UV rays and ozone can cause the saturating resin to age and discolor over time.
· Fire Resistance: For projects requiring fire protection, apply an asbestos-free mortar or cement mortar finish. To improve mechanical bonding, broadcast pea gravel or grit onto the wet topcoat before it cures to create a roughened surface.
· Impact Protection: In areas subject to vehicle impact or physical abrasion, install a protective mortar layer or a mesh-reinforced high-strength concrete layer. Ensure the protective coating achieves sufficient bond strength with the fiber wrap.
· Aesthetics: If decorative finishing is required, use pigmented resins or specialized color coatings.

Quality Assurance & Inspection (QA/QC)

3.1 Pre-construction Verification: 

Confirm that all carbon fiber sheets, adhesives, primers, and leveling materials have valid product certifications and quality test reports. All performance metrics must meet the relevant acceptance codes.

3.2 Material Sampling & Testing:

· Carbon Fiber Sheets: For projects exceeding 1000㎡ , provide one test report (tensile strength and elastic modulus) per 1000 ㎡. Each test requires at least 3 sets of 5 samples. For smaller projects, a test report from the same batch used in a different project within the current year is acceptable; otherwise, one set must be tested.
· Adhesives: For quantities under 1 ton, perform one set of pull-off bonding strength tests. Add one set per additional ton. Each set must contain at least 5 samples. Samples must be randomly selected from at least two separate packaging units by an independent lab technician.

3.3 Defect Remediation: 

If the bonding quality is substandard (e.g., hollows/voids), the affected carbon fiber must be cut away along the edge of the void. Patch the area using the same material and adhesive, ensuring the patch extends 100mm beyond the repair edge in all directions.

3.4 Failure to Meet Strength Requirements: 

If the pull-off bonding strength fails to meet specifications, all carbon fiber composites represented by that sampling lot must be stripped off and completely redone.

Professional Equipment & Tools

1. Substrate Preparation Tools

· Grinder: For smoothing the concrete surface.
· Chisel: For removing loose concrete debris and residues.
· Wire Brush: For cleaning stains and surface contaminants.

2. CFRP Application Tools

· Mixing Containers: For blending epoxy resin components.
· Scales: For precise weighing of resin and hardener.
· Agitator/Mixer: For mechanical mixing of resin materials.
· Scraper/Squeegee: For leveling surface defects and smoothing fiber sheets.
· Roller Brush: For applying resin primers and coatings.
· Laminating Roller (Roller): For de-foaming and pressing the carbon fiber.

3. Inspection & Measurement Tools

· Straightedge: For checking concrete surface flatness.
· Feeler Gauge: Used in conjunction with the straightedge for gap measurement.
· Thermo-Hygrometer: For monitoring ambient temperature and humidity.
· Inspection Hammer: For detecting hollow spots (delamination) via sound.
· Tape Measure & Steel Ruler: For dimensional layout and verification.

4. Repair Tools

· Injector/Syringe: For injecting resin into hollow areas or voids.
· Cutter/Utility Knife: For slitting fiber sheets during void repair.

5. Personal Protective Equipment (PPE)

· Work Clothes & Caps
· Safety Goggles
· Dust Masks
· Hard Hat (Safety Helmet)
· Rubber Gloves