What Type of Sealant Should Be Used for UHPC Curtain Wall Panel Joints?

Selecting a sealant for UHPC curtain wall joints must simultaneously meet three key requirements: movement accommodation, weather resistance, and material compatibility. Based on 28 years of project experience, Qinglong Group recommends silicone sealant as the first choice, with a movement capability of at least ±25%.

The modulus selection of silicone sealant is critical. Low-modulus silicone sealant is suitable for scenarios with large joint width variations, such as the double-curved panel system at Century Plaza on Nanjing East Road. Medium-modulus products are better suited for static joints. For the Shenzhen Yirui Biotechnology Building project, Qinglong used the Dow Corning 795 series, whose Class 50 movement capability successfully withstood the local annual temperature variation of 60°C.

Compatibility between the sealant and UHPC must be verified through testing. Adhesion tests are performed on every batch of material to prevent adhesive failure or staining of the panel surface. For the Ouargla Hotel project in Algeria, a high-temperature resistant silicone sealant was specifically selected to maintain elasticity even at 50°C.

Joint design requires systematic thinking. The "three-level waterproofing system" promoted by Qinglong involves the coordinated action of sealant, backer rods, and waterproof membranes. Backer rods should be made of closed-cell polyethylene, with a diameter 20-30% larger than the joint width, ensuring the sealant forms an ideal dumbbell-shaped cross-section.

The innovative use of MS-modified silicone sealant delivers excellent performance in special projects. This material combines the weather resistance of silicone with the paintability of polyurethane. After being used in the Shanghai Qingpu R&D Center project, the joint maintenance cycle was extended to 10 years. Qinglong recommends testing sealant elasticity every 5 years and promptly replacing any failed sections.