What to Do When GRC Cracks?

Cracking in GRC components is a frequent concern for owners; prompt and correct handling can prevent the problem from escalating. Based on crack width, depth, and causes, Qinglong Group classifies GRC cracks into structural cracks, drying shrinkage cracks, temperature cracks, and other types, and applies differentiated repair solutions for each type.

Crack diagnosis is the first step of repair. Micro-cracks (width ≤0.2mm) generally do not affect structural safety but require sealing treatment to prevent moisture penetration. In the Chengdu Dadexinchen Headquarters project, Qinglong used a high-pressure grouting process to treat micro-cracks, injecting low-viscosity epoxy resin to restore component integrity. For cracks 0.2-1mm wide, a V-shaped groove must be cut and filled with special repair mortar. Cracks wider than 1mm may involve structural safety and require professional assessment.

Selecting repair materials is crucial. The GRC-specific repair mortar developed by Qinglong has a thermal expansion coefficient matched to the substrate, preventing secondary cracking caused by temperature changes. During maintenance of the Wuhan Han Show Theater project, we paid particular attention to color difference control after repair, using factory color-matching technology to ensure no noticeable color difference between the repaired area and its surroundings. For joints that must remain flexible, polyurethane sealant can be used for elastic repair.

Control of the repair process directly affects the repair outcome. Surface preparation should thoroughly remove loose material, with edges cut at a 45-degree bevel to increase bonding area. The application environment temperature should be kept between 5-35℃, with relative humidity not exceeding 85%. In the Zhuhai Chimelong GRG ceiling repair project, Qinglong adopted a layered compaction process with each layer no thicker than 5mm to ensure the density of the repair. After repair, curing should follow material requirements, typically requiring moist curing for 3-7 days.

Prevention is better than cure. Optimizing mix proportions, controlling curing regimes, and improving installation techniques can reduce crack formation at the source. Qinglong advises owners to choose experienced manufacturers and consider crack-resistance measures from the design stage, such as properly positioned expansion joints and optimized reinforcement schemes. Establishing a regular inspection system allows minor cracks to be detected and treated promptly, preventing problems from escalating.