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

The thermal expansion and contraction problem of UHPC curtain walls is essentially caused by temperature changes inducing linear expansion and contraction of the material, which in turn generates thermal stress within the system; if not handled properly, this can lead to panel warping, joint cracking, or even connection failure. The core approach to solving this problem is not to completely prevent deformation, but to guide and safely release thermal stress through four major strategies: "scientifically designing deformation space, adopting flexible connection systems, optimizing material performance, and properly setting expansion joints." In the Wuxiang China Resources MixC project in Nanning, Qinglong Group calculated and reserved a 15mm panel joint width and adopted high-elasticity sealant, successfully meeting the challenge of a local annual temperature variation of nearly 50℃.

Calculating and Reserving Sufficient Deformation Space is the Design Foundation

First, the maximum deformation of components must be calculated based on the extreme temperature difference at the project location (the difference between the annual maximum and minimum temperatures) and the linear expansion coefficient of UHPC (approximately 10-12×10⁻⁶/℃). For example, a 3-meter-long UHPC panel in an environment with a 50℃ temperature difference will have a length change of ΔL = 3000mm × 12×10⁻⁶/℃ × 50℃ = 1.8mm. In the design, the panel joint width must be greater than this deformation amount, while considering multiple factors such as construction tolerances and wind load displacement. Qinglong typically sets the standard panel joint width between 12-20mm, providing ample space for thermal deformation.

Adopting Flexible Connections and Adjustable Anchor Systems

The connection system must feature "rigid connection with flexible adaptation." The three-dimensionally adjustable stainless steel anchors used by Qinglong have a certain adjustment margin in the X, Y, and Z directions, allowing panels to undergo slight displacement under temperature effects and preventing the formation of restraint stress. The connection between anchors and framing members should preferably use slotted holes with elastic washers, ensuring both load-bearing capacity and sliding capability. The connection points between embedded parts and anchors should also avoid rigid welding, using bolted connections instead to allow slight rotation.

Optimizing the Material Mix to Reduce Thermal Expansion Coefficient and Shrinkage

Starting with the material itself, temperature sensitivity can be reduced through mix proportion design. Incorporating an appropriate amount of low thermal expansion aggregates such as quartz sand and calcined bauxite can optimize the material's thermal performance. At the same time, the autogenous shrinkage and drying shrinkage of UHPC must be strictly controlled; by adding internal curing agents or expansive components, the material's inherent volume instability is reduced, lowering the risk of superimposed stress at the source. This optimization is especially important in regions with large day-night temperature differences.

Setting Up Systematic Expansion Joints and Deformation Units

For large-area continuous curtain walls, vertical and horizontal expansion joints must be set in accordance with standards, dividing the curtain wall into several independent deformation units. Special sliding supports and telescopic cover plates should be installed at expansion joints to ensure that larger cumulative deformation can be absorbed there. For curtain wall facades exceeding 30 meters in length, Qinglong sets an expansion joint every 15-20 meters, effectively releasing the thermal stress of the overall structure.

Therefore, solving the thermal expansion and contraction of UHPC curtain walls is a systematic design issue that requires the close integration of materials, construction details, calculation, and installation. Through precise calculation and meticulous joint detailing, Qinglong Group ensures that every UHPC panel can "breathe" freely throughout its life cycle of temperature changes, maintaining the long-term safety and aesthetics of the curtain wall system.