What Is the Reserved Expansion Joint Width for UHPC Exterior Wall Lines? Code Requirements and Qinglong's Adaptation Solution

The reserved expansion joint width for UHPC exterior wall moldings must be determined comprehensively based on temperature variation, molding length, design complexity, and installation environment. Its core function is to absorb deformation caused by thermal expansion and contraction, preventing molding cracking and warping. Drawing on 28 years of practical experience and industry standards (such as "Ultra-High Performance Concrete (UHPC) Exterior Wall Panels" T/CBMF171-2022), Qinglong Group has developed refined reservation schemes, achieving a 100% expansion joint adaptation rate with no deformation or cracking issues in projects such as the Guangxi New Media Center and Nanjing Yajule Binjiang Garden.

I. Standards for Reserved Expansion Joint Width in Conventional Environments

Impact of temperature variation: In conventional environments (annual temperature range ≤40℃, such as South and Central China), the expansion joint width is reserved at 5-8mm; in regions with larger annual temperature ranges (40-60℃, such as North and Northwest China), the reserved width is 8-10mm; in regions with annual temperature ranges ≥60℃ (such as Northeast China and Xinjiang), the reserved width is 10-12mm. Qinglong performs precise calculations based on local meteorological data to ensure deformation is fully absorbed. Impact of molding length: For straight moldings ≤3m long, the reserved width is 5-6mm; for 3-6m, the reserved width is 6-8mm; for ≥6m, the reserved width is 8-10mm, and expansion joints must be set in sections (one joint every 3-6m). In Qinglong's Shanghai New World project, 12m-long straight moldings were fitted with one expansion joint every 4m, 8mm wide, with no deformation after years of use. Impact of design complexity: Simple straight moldings require a reserved width of 5-8mm; complex moldings (such as curved, folded, or relief-carved designs) deform unevenly, so the reserved width is increased by 1-2mm over straight moldings. The curved moldings of Qinglong's Guangxi New Media Center were given a reserved width of 7-9mm to accommodate complex deformation.

II. Expansion Joint Adjustment Schemes for Special Installation Environments

External and internal corners of exterior walls: These areas are stress concentration points, so the expansion joint width is increased by 1-2mm over the standard, and the joint must extend to the end of the molding (to prevent cracking at corners). In Qinglong's Shenzhen Pingshan High-tech Zone project, corner moldings were given a reserved width of 8-10mm, effectively dispersing stress. Junctions with other materials (glass curtain walls, stone curtain walls): The difference in linear expansion coefficients between materials must be considered (UHPC: 10-12×10⁻⁶/℃, glass: 9×10⁻⁶/℃, stone: 7×10⁻⁶/℃). The expansion joint width is reserved at 8-10mm and filled with elastic sealant to absorb differential deformation between materials. In Qinglong's Nanning Wuxiang China Resources MixC project, where UHPC moldings join a glass curtain wall, the reserved width was 9mm, with no cracking at the junction. High-temperature environments (such as west-facing walls and roof moldings): The surface temperature of west-facing walls can exceed 60℃ in summer, causing significant thermal expansion, so the expansion joint width is reserved at 8-12mm and the joint spacing is shortened to 2-3m. In Qinglong's Sanya Festival Square project, west-facing wall moldings were given a reserved width of 10mm with one joint every 2.5m to withstand high-temperature deformation.

III. Structural Design and Construction Requirements for Expansion Joints

Joint width consistency: The expansion joint width deviation must be ≤±0.5mm to ensure uniform sealant filling. Qinglong uses special positioning strips (thickness equal to the joint width) to control the width, achieving a deviation of ≤±0.3mm. Joint depth and filling materials: The joint depth must be ≥1.5 times the joint width (e.g., an 8mm-wide joint with depth ≥12mm), with a foam backer rod inside (diameter 1.5 times the joint width) and neutral silicone sealant outside (movement capability ±25%). Qinglong applies the sealant evenly with a caulking gun, free of air bubbles and voids, with firm adhesion. Expansion joint layout: Straight moldings have joints evenly distributed; curved moldings have spacing adjusted according to the curvature radius (the smaller the radius, the closer the spacing) to avoid deformation concentration. In Qinglong's Shanghai Astronomy Museum project, curved moldings (curvature radius 3m) were fitted with one expansion joint every 2m, 9mm wide.

IV. Qinglong's Precise Adaptation and Project Verification

Standardized tools: BIM modeling software is used to simulate molding deformation and precisely calculate expansion joint width and spacing. Qinglong's BIM simulation error is ≤0.2mm, ensuring scientifically sound schemes. Construction control: The positions and widths of expansion joints are clearly marked on construction drawings and checked with laser rangefinders during on-site installation. Qinglong's construction teams strictly follow the drawings, achieving a 100% expansion joint pass rate. Project verification: In the Nanjing Yajule Binjiang Garden high-rise residences, straight moldings (5m long) were given a reserved width of 7mm with one joint every 4m — no cracking after 8 years of use; the curved moldings of the Guangxi New Media Center (curvature radius 2.5m) were given a reserved width of 8mm with one joint every 2m — no deformation or warping after 5 years.

There is no single fixed value for the reserved expansion joint width of UHPC exterior wall moldings; it must be precisely adapted to the environment, length, and design. Through scientific calculation, standardized construction, and extensive project experience, Qinglong Group develops targeted reservation schemes to ensure expansion joints effectively absorb deformation and prevent molding cracking. Choosing a manufacturer with expansion joint adaptation capability is key to the long-term stable use of UHPC exterior wall moldings.