What Gap Width Should Be Reserved When Splicing UHPC Panels? Gap Allowance Standards and Sealing Solutions

The width of UHPC panel joint gaps directly affects the installation result and structural stability. If the reserved gap is too small, thermal expansion and contraction can easily cause panels to be squeezed and crack; if too large, it compromises aesthetics and waterproofing performance. Scientifically determining the gap width, combined with a compatible sealing solution, is key to ensuring UHPC panel jointing quality. Drawing on jointing experience from projects such as Shanghai Xinghewan and Shenzhen Pingshan High-tech Zone, Qinglong analyzes the core standards and practical solutions.

I. Core Basis for Determining UHPC Panel Joint Gap Width

The gap width must be determined comprehensively based on thermal deformation, panel dimensions, and installation accuracy. Thermal deformation is the core influencing factor: the linear expansion coefficient of UHPC panels is approximately 10×10⁻⁶/℃, and the deformation should be calculated based on the local extreme temperature difference. The gap width must be ≥ thermal deformation + installation error. In ordinary regions, the extreme temperature difference is calculated at 40℃; a 10m-long UHPC panel has a thermal deformation of about 4mm, with 2mm reserved for installation error, giving a base gap width of ≥6mm. Regarding panel dimensions, the longer the panel, the greater the required gap width—for every 5m increase in length, the gap width increases by 2-3mm. Regarding installation accuracy, where precision control is at a high level, the gap width can be appropriately reduced, but in no case less than 5mm. In the Yangshengtang Pharmaceutical Hangzhou Industrial Park project, Qinglong reserved 8mm for the joints of 12m-long UHPC panels, meeting the deformation requirements.

II. Gap Width Reservation Standards for Different Scenarios

Reserve the gap width precisely according to the application scenario and environmental conditions. Indoor scenarios: stable ambient temperature and small temperature differences—reserve a gap width of 5-8mm; ordinary outdoor scenarios: larger temperature differences—reserve a gap width of 8-12mm; coastal high-humidity or high-temperature sun-exposed areas: dual influence of temperature and humidity deformation—reserve a gap width of 10-15mm; large-span panels (length >10m): reserve a gap width of 12-15mm, with expansion joints installed at intervals of ≤10m; special-shaped panels (such as double-curved panels and curved panels): due to complex shapes and larger installation errors, reserve a gap width of 10-12mm. For the double-curved panel jointing at the Guangxi New Media Center, Qinglong followed these standards with good results.

III. Core Sealing Solutions and Material Selection

The sealing solution must address waterproofing, deformation resistance, and aesthetics, while material selection must match the gap characteristics. Silicone structural sealant or polysulfide sealant is preferred as the sealing material, offering excellent weather resistance and elasticity with a movement capability of ≥±25%, able to accommodate the thermal expansion and contraction of UHPC panels. In the Shanghai Astronomy Museum project, Qinglong selected high-modulus silicone sealant, achieving excellent sealing performance and durability. The sealing structure adopts a dual seal of “foam backer rod + sealant”: the foam rod diameter is 20% larger than the gap width to ensure full filling, and the sealant thickness is 1/2-2/3 of the gap width and ≥6mm. Decorative strips can be added to the surface as needed, enhancing aesthetics while protecting the sealant from UV-induced accelerated aging.

IV. Practical Points for Gap Reservation and Sealing

Standardized operations ensure precise gap reservation and reliable sealing. During installation, dedicated positioning spacer blocks are used to control the gap width; the spacers are made of hard rubber, with a thickness equal to the gap width and spacing ≤1m. The gaps must be cleaned thoroughly, removing dust, debris, and moisture to ensure firm sealant adhesion. The foam rod is embedded in the middle of the gap, kept centered to avoid offset. The sealant is applied evenly with dedicated tools, ensuring full, smooth sealant joints free of bubbles and cracking. After sealant application, let it cure undisturbed; avoid impacts and rain washing during curing, with a curing time of no less than 7 days. Through standardized operations, Qinglong ensures a pass rate of over 99% for joint sealing, effectively avoiding leakage and deformation risks.