UHPC Exterior Wall Line Expansion Joints: Reserved Width and Installation Specifications Explained

Although UHPC materials have good dimensional stability, temperature changes can still cause thermal expansion and contraction. Properly setting expansion joints is key to avoiding cracking and deformation of exterior wall mouldings. Qinglong Group, with 28 years of experience in UHPC/GRC/GRG/GRP detailed design, has developed scientific specifications for the reservation and installation of expansion joints in UHPC exterior wall mouldings based on extensive project practice.

#Expansion Joint Reserved Width: Precise Calculation Based on Environment and Length The reserved width of expansion joints for UHPC exterior wall mouldings must be determined comprehensively based on the service environment and the moulding length. In normal temperature environments (-10°C to 35°C), straight UHPC exterior wall mouldings require a 10-15mm expansion joint for every 6-8 meters of length; if the moulding length exceeds 10 meters, the reserved width must be increased to 15-20mm. In regions with large temperature differences (extreme temperature variations exceeding 40°C), such as severe cold regions in the north or intensely hot regions in the south, the reserved width of expansion joints should be appropriately increased: straight mouldings require 15-20mm every 6 meters, and 20-25mm for lengths over 10 meters. For irregular UHPC exterior wall mouldings such as curved or angular profiles, since expansion and contraction deformation is more complex, the reserved width needs to be 20%-30% larger than that of straight mouldings. In the Shanghai Xinghewan project, Qinglong Group reserved a 12mm expansion joint for an 8-meter straight UHPC exterior wall moulding, which has shown no cracking or deformation after years of use.

#Expansion Joint Spacing: Scientifically Divided by Moulding Type The spacing of expansion joints must be adjusted according to the type and installation method of the UHPC exterior wall mouldings. For horizontal UHPC exterior wall mouldings (such as waist lines and cornice lines), the expansion joint spacing is recommended to be kept at 6-8 meters; for vertical mouldings (such as columns and decorative mouldings), the spacing can be relaxed to 8-10 meters. If mouldings are installed in segments or joined with other materials, expansion joints must be set at the joints. For UHPC exterior wall mouldings with complex shapes and large cross-sections (cross-section width exceeding 300mm), since thermal expansion and contraction deformation is greater, the expansion joint spacing must be shortened to 5-6 meters. In the Dongguan Women and Children's Activity Center project, Qinglong Group set expansion joints at 5-meter intervals for UHPC exterior wall mouldings with complex shapes, effectively releasing deformation stress.

#Expansion Joint Structural Design: Balancing Function and Aesthetics The structural design of expansion joints must simultaneously meet requirements for deformation, waterproofing, and aesthetics. Qinglong Group adopts a "flexible sealing + decorative cover plate" construction scheme: the interior of the expansion joint is filled with highly weather-resistant, highly elastic silicone sealant, and the sealant must have good compatibility with UHPC materials to ensure secure bonding. The sealant filling depth must be no less than 20mm, with a certain deformation allowance reserved to meet the expansion and contraction needs of the UHPC mouldings. A decorative cover plate is installed on the outer side of the sealant; the cover plate material should be consistent with or coordinated with the UHPC moulding, and a 3-5mm movement gap is reserved between the cover plate and the moulding to ensure it does not hinder expansion and contraction. The decorative cover plate uses a snap-fit installation for easy later maintenance and replacement. In the Hainan International Convention and Exhibition Center project, this structural design effectively released deformation stress while ensuring the overall aesthetic appearance of the exterior wall.

#Special Scenario Settings: Targeted Solutions In special scenarios, the expansion joint settings for UHPC exterior wall mouldings require dedicated optimization. When a moulding crosses a building expansion joint, it must be kept synchronized with the main building expansion joint, with a reserved width no less than that of the main building expansion joint. At corners, door and window openings, and similar locations, expansion joints must be set 200-300mm away from the corner or opening to prevent deformation stress from affecting the structure around the opening. For super-long continuous UHPC exterior wall mouldings where design constraints make conventional expansion joints impossible, methods such as installing sliding supports or elastic connections can be adopted to release deformation stress. In the Guangxi New Media Center project, Qinglong Group adopted a solution combining sliding supports with elastic sealing for super-long irregular UHPC exterior wall mouldings, successfully solving the deformation problem.

Setting expansion joints for UHPC exterior wall mouldings is a key detail in safeguarding project quality and requires scientific planning based on multiple factors including environment, length, and shape. With 28 years of detailed design experience, Qinglong Group provides precise expansion joint solutions for every project. Through scientific reserved widths and structural design, both the functional performance of UHPC mouldings and the aesthetic appearance of the building are ensured. Only by choosing a professional UHPC manufacturer can you obtain comprehensive technical support and avoid quality problems caused by improper expansion joint settings.