Key Technical Points for Renovating GRC Components on Existing Buildings: Repair, Reinforcement and Appearance Enhancement

Renovating and retrofitting GRC components on existing buildings is a more challenging undertaking than new construction. It involves assessing, repairing, reinforcing, and even replacing old components, while balancing the preservation of the building's architectural character with performance improvement. Through numerous historic building preservation and commercial renovation projects, Qinglong Group has built up a systematic renovation technology framework.

1. Comprehensive Inspection and Evaluation: This is the foundation of all work. Multiple methods—visual inspection, tapping, infrared thermography, ultrasonic testing, core sampling, and more—must be employed to scientifically evaluate the damage types (cracks, spalling, corrosion, weathering), damage extent, structural safety, and substrate condition of existing GRC components. Meanwhile, samples should be taken to analyze material properties (strength, carbonation depth, chloride ion content, etc.), providing a basis for selecting repair materials.

2. Damage Repair Techniques: ◦Crack treatment: For micro-cracks narrower than 0.2mm, surface sealing can be applied (brushing on a flexible waterproof coating); for active cracks, low-viscosity epoxy resin injection is used for sealing and strengthening; for structural cracks, after injection, carbon fiber fabric or steel plates must be bonded to the surface for reinforcement. ◦Defect repair: Chisel away loose portions, remove rust from and apply anti-rust treatment to exposed rebar, then repair in layers with polymer-modified mortar or a dedicated GRC repair compound, ensuring a strong bond between the new and old interfaces; where necessary, anti-rust bolts or fiber mesh can be added for reinforcement. ◦Efflorescence and stain removal: Use dedicated cleaning agents together with a low-pressure water gun; strong acids are strictly prohibited. For stubborn stains, sandblasting may be performed.

3. Structural Reinforcement and Connection Retrofit: Components with insufficient load-bearing capacity or loose connection systems must be reinforced. Methods include adding steel frame supports to the back of components, upgrading to higher-grade connectors, and strengthening the base structure. In the renovation of an old theater in Shenzhen, we carried out comprehensive rear steel-frame reinforcement of the cornice GRC moldings, ensuring their long-term safety.

4. Protection and Decorative Renewal: After repairs are completed, new protective coatings (such as fluorocarbon paint or silane impregnants) or new finish effects (such as recoloring or stone-effect coatings) can be applied according to the building's new requirements. This not only enhances aesthetics but also greatly extends the service life of the components.

5. Partial Replacement and Old-New Integration: For severely damaged components that cannot be repaired, customized replacement is required. 3D scanning technology is used to capture the precise shape of the old components, and molds are made for replication, ensuring that new and old components are consistent in shape, texture, and color. The success of a renovation lies in precisely grasping the principle of "restoring the old as old, upgrading performance."