How to Solve the Thermal Expansion and Contraction Problem of UHPC Curtain Walls?

The thermal expansion and contraction issues of UHPC curtain walls can be resolved through three core approaches: “design optimization, material improvement, and flexible joint treatment”, with the core control target being deformation ≤L/500 (L is the panel edge length). Drawing on 28 years of engineering experience, Qinglong ensures UHPC curtain walls remain free of cracking and leakage under temperature differences from -40℃ to 80℃, with multiple high-altitude, large-temperature-difference projects running stably.

I. Design Optimization: Reserving Space for Deformation

Risks of thermal expansion and contraction are mitigated in advance at the design stage. Expansion joint placement: expansion joints are set according to temperature differences and panel dimensions, with joint spacing ≤30m in conventional environments and ≤25m in large-temperature-difference environments, and joint widths of 20-30mm. In Qinglong's Hainan Changying Universal 100 project, the expansion joint spacing is 25m, suited to tropical temperature differences. Panel subdivision: large-area curtain walls are divided into small modules (single panel area ≤6㎡) to reduce deformation per panel; Qinglong's deformation was reduced by 30% after module subdivision. Shape adaptation: double-curved and arc shapes release deformation stress more easily than flat panels; the double-curved UHPC curtain wall of Qinglong's Guangxi New Media Center exhibits uniform thermal expansion and contraction deformation without stress concentration.

II. Material Improvement: Enhancing Deformation Resistance

Optimized material formulations enhance inherent deformation resistance. Fiber content adjustment: steel fiber/alkali-resistant glass fiber content is raised to 2.5-3.0%, enhancing UHPC tensile strength and toughness; Qinglong UHPC has flexural strength ≥18MPa and elongation at break ≥0.5%, with deformation resistance improved by 40%. Cementitious system optimization: silica fume and ultra-fine fly ash are added (total 20-30%) to reduce hydration heat and shrinkage; Qinglong UHPC has a drying shrinkage rate ≤0.025% and a thermal expansion coefficient ≤12×10⁻⁶/℃. Surface treatment: silane impregnation is applied to reduce the impact of temperature changes on the surface; after surface treatment, Qinglong UHPC withstands ≥300 freeze-thaw cycles without cracking.

III. Flexible Joint Treatment: Releasing Deformation Stress

Joint designs provide buffer space for deformation. Flexible connection: a “hanger + elastic gasket” connection is adopted, with gaskets made of butyl rubber (compression deformation rate ≤10%) allowing ±5mm displacement; Qinglong's flexible joints can release over 80% of thermal expansion and contraction stress. Sealant selection: high-elasticity sealants (elongation ≥500%) are used to accommodate joint deformation; Qinglong uses neutral weather-resistant silicone sealant, which shows no cracking or peeling after deformation. Substrate adaptation: a 5-10mm gap is reserved between the steel frame keels and UHPC panels to avoid rigid restraint; Qinglong fills the gap with thermally insulating elastic material, combining insulation with deformation accommodation. Project case: the UHPC curtain wall of the Library Information Center of Dali University in Yunnan is located in a high-altitude environment with large temperature differences; using the above solutions, it has operated for 10 years without cracking or leakage caused by thermal expansion and contraction.