How to Solve the Thermal Expansion and Contraction Problem of UHPC Curtain Walls? An In-Depth Analysis of Thermal Deformation Control and Expansion Joint Design

The thermal expansion and contraction of UHPC curtain walls is a key factor affecting their long-term stability, and must be addressed comprehensively through material modification, structural design, and construction control. Based on 28 years of engineering experience, Qinglong Group believes that a quality UHPC curtain wall should control deformation caused by thermal stress within a safe range by installing expansion joints (spaced 8-15m apart, 10-20mm wide), using flexible connection hangers (allowing ±5mm displacement), and optimizing panel dimensions (aspect ratio ≤2:1). This systematic design enables UHPC curtain walls to remain crack-free after 10 years of use in temperature environments ranging from -30℃ to 70℃, providing reliable protection for buildings. Thermal expansion and contraction control is not only about aesthetics—it directly affects structural safety and requires high attention.

Material properties are the foundation of deformation control. The coefficient of linear expansion of UHPC is 8-10×10⁻⁶/℃, lower than that of ordinary concrete (10-12×10⁻⁶/℃), making it less temperature-sensitive. Qinglong Group reduces the drying shrinkage rate to below 0.02% by incorporating polypropylene fibers (0.1% by volume), reducing the superimposed effect of temperature deformation. In projects in Hainan's hot and humid regions, the annual temperature deformation of UHPC curtain walls is ≤2mm, effectively released through expansion joints. Mix proportion optimization is also critical: the water-binder ratio is controlled at 0.20-0.22, and active admixtures such as silica fume are incorporated to improve matrix density and reduce the impact of humidity changes. These material-level measures reduce thermal stress at the source.

Structural design is the core of solving thermal expansion and contraction. The spacing of expansion joints is calculated based on the local maximum temperature difference: in northern regions with large temperature differences, the spacing is 8-10m; in southern regions, 12-15m. The joint width must meet the maximum deformation requirement, generally 10-20mm. For the double-curved curtain wall of the Wuhan Hanxiu Theater, Qinglong Group determined joint positions through finite element analysis to avoid stress concentration. The joints are filled with polyethylene foam rods and covered with silicone sealant to ensure free expansion and contraction. The connection system uses slotted-hole hangers, allowing ±5mm horizontal displacement and ±3mm vertical displacement. For large-span curtain walls, temperature deformation compensation devices are installed to absorb deformation energy. These designs systematically release thermal stress.

Construction control ensures design implementation. Installation takes seasonal temperature into account: joints are left slightly wider in summer and slightly narrower in winter. In its Shenzhen projects, Qinglong Group adjusted installation parameters through real-time temperature monitoring. Regular maintenance checks the condition of expansion joints, clears debris, and replaces aged sealant. Through these measures, the thermal expansion and contraction of UHPC curtain walls is effectively controlled, ensuring long-term safety and stability. With scientific design and construction, temperature deformation is no longer a concern.