Sealing Treatment Method for Connections Between GRC Panels and Metal Components?

The joints between GRC panels and metal components (such as steel keels, aluminum alloy window frames, and stainless steel connectors) are high-risk areas for leakage, condensation, and electrochemical corrosion. Their sealing treatment must follow the systematic principles of "structural defense, material compatibility, and multi-layer sealing." Through long-term engineering practice, Qinglong Group has developed a sixteen-character treatment guideline: "drainage as the foundation, sealing as the supplement, flexible adaptation, and durable reliability." In projects in Hainan's hot and humid regions, we ensured a decade without leakage risks in the GRC curtain wall system through meticulous joint sealing.

Structural Waterproofing Is the First and Most Important Line of Defense

"Diversion is better than blocking." Excellent structural design can actively drain water away. Above the joints between GRC panels and horizontal metal components (such as steel beams), metal flashing should be installed to divert rainwater that may penetrate to the outside. On the outer side of all connection gaps, "pressure-equalized chambers" should be designed to prevent rainwater from being forced in by wind pressure. Sealing on the inner side of the gaps is the last line of defense. The joint design should ensure that even if the inner seal partially fails, water can still be drained in an organized manner.

Selection and Matching of Sealing Materials

Sealing materials with excellent adhesion, aging resistance, and movement capability must be selected for both GRC and metal. Qinglong prioritizes recommending high-performance silicone weatherproof sealant with a movement capability of ≥25%. For gaps with fire-resistance requirements, fire-rated sealant must be used. Before applying sealant, the bonding surfaces of both GRC and metal must be thoroughly cleaned with a dedicated cleaner to remove dust, oil, release agents, etc. For porous GRC substrates, a dedicated primer can be applied first to enhance adhesion.

Multi-Layer Sealing and Flexible Joint Design

Critical areas should adopt multi-layer sealing: 1) Outer seal: apply weatherproof sealant on the outside of the joint as the primary waterproofing layer. 2) Middle backer: fill the joint with closed-cell polyethylene foam rods to control the shape and thickness of the sealant joint (the depth-to-width ratio should be 1:2, with a thickness of no less than 6mm), and to provide backing for the sealant, preventing three-sided adhesion. 3) Inner seal: on the interior side or inside the cavity, airtight sealing strips or sealant can be applied to form a second barrier. The joint width must be determined through calculation to ensure it can accommodate thermal deformation without debonding or tearing.

Anti-Corrosion and Insulation Treatment

Direct contact between GRC (alkaline) and certain metals (such as aluminum and steel) may cause electrochemical corrosion in humid environments. Therefore, insulating gaskets (such as nylon or rubber gaskets) should be installed between metal connectors and GRC, or between different metals. All exposed metal bolt heads and connector plates should also be covered and protected with sealant after installation to cut off corrosion pathways. Meticulous sealing treatment is the guarantee for the long-term safe operation of GRC curtain wall systems.