What Should Be Noted in UHPC Construction? Eight Key Points to Ensure Ultra-High Performance Concrete Construction Quality

"The success or failure of UHPC construction lies in the precise control of every detail"—this is the valuable experience Qinglong has accumulated over 28 years in the field of UHPC/GRC/GRG/GRP material construction and installation. As a leading enterprise that participated in formulating industry standards such as the "Ultra-High Performance Concrete (UHPC) Exterior Wall Panel", Qinglong has undertaken numerous major projects including the Shanghai Astronomy Museum and the Yangshengtang Pharmaceutical Hangzhou Industrial Park, gaining a deep understanding of the decisive role that detail control in UHPC construction plays in project quality. The following eight key points are the core of ensuring UHPC construction quality, and are also the areas that designers and owners need to focus on during project advancement.

Pre-construction preparation is the foundation, requiring triple guarantees in materials, equipment, and technology. In terms of materials, UHPC raw materials must be procured strictly according to formula requirements, with sampling inspections conducted before entering the site to ensure that aggregate purity, fiber length, admixture performance, etc. meet standards; Qinglong implements a "double inspection system" for every batch of raw materials, controlling quality at the source. In terms of equipment, dedicated mixing equipment, pouring molds, curing facilities, and lifting tools must be equipped—the mixing equipment must ensure uniform mixing, the molds must have sufficient rigidity and flatness, and the curing facilities must be able to precisely control temperature and humidity. In terms of technology, detailed design and construction plan preparation must be completed, BIM technology must be used to simulate the construction process and clarify key items such as component segmentation, installation nodes, and construction sequence, and specialized training must be provided to construction personnel to ensure they are familiar with material characteristics and operating specifications. In the Huawei Bantian Headquarters project in Shanghai, Qinglong completed technical preparations 3 months in advance and optimized installation nodes through BIM modeling, laying a solid foundation for the smooth progress of construction.

The mixing process must be precisely controlled to ensure material uniformity and fluidity. The mixing quality of UHPC directly affects its mechanical properties. When mixing, materials must be fed strictly in the order of "aggregate → cement → reactive powder → admixture → water → fiber". The mixing time must be adjusted according to equipment type and material mix ratio, generally 6-10 minutes, to ensure that fibers are evenly dispersed without agglomeration. Qinglong uses automated twin-shaft mixing equipment, precisely controlling the feeding sequence and mixing time through computer programs, achieving fiber dispersion uniformity of over 98%; during mixing, the fluidity of the mixture must be monitored in real time—if fluidity is insufficient, the admixture dosage can be appropriately adjusted to ensure smooth pouring. It should be noted that UHPC mixtures have a short initial setting time, so pouring must be completed within 45 minutes after mixing to avoid compromising construction quality due to initial setting.

Pouring operations require attention to detail to ensure component molding quality. Before pouring, the mold surface must be cleaned and coated with a dedicated release agent to ensure a smooth component surface without mold sticking; the appropriate pouring method should be selected according to the component shape—flat plate components can adopt the layered pouring method with each layer no thicker than 50mm, while complex curved or thin-walled components can adopt the spray pouring method, controlling the pouring speed to avoid bubbles; during pouring, vibration equipment should be used in coordination to remove bubbles, with vibration time determined by when mortar appears on the mixture surface and no obvious bubbles emerge, while avoiding over-vibration that causes aggregate segregation; for complex components such as hollow-outs and carvings, dedicated tools must be used to assist pouring to ensure the material fills completely. In the Ouargla Hotel project in Algeria, Qinglong customized dedicated pouring tools for the construction requirements of UHPC hollow panels, ensuring a hollow-out rate exceeding 50% with uniform filling and a smooth, refined surface.

Curing is a critical stage that determines UHPC strength and durability. UHPC has a low water-binder ratio and high early shrinkage; improper curing can easily lead to cracks that affect performance. After pouring, moisturizing materials must be promptly applied to prevent water evaporation, and spray curing can be adopted after initial setting to keep the surface moist; for components with high strength requirements, steam curing or constant temperature and humidity curing is recommended, with curing temperature controlled at 20-40℃ and humidity no lower than 90%, and a curing period of no less than 7 days to ensure stable strength development. Qinglong's self-developed intelligent curing kiln can precisely control temperature and humidity, achieving fully automated curing. In the Shanghai Astronomy Museum public art project, through scientific curing, the UHPC sculpture achieved a compressive strength of 180MPa, far exceeding design requirements. In addition, during the curing period, components must be protected from collision or loading to prevent cracking.

Installation precision must be strictly controlled to ensure component connections and overall effect. UHPC component installation must follow the principle of "positioning first, then fixing", using 3D laser scanning positioning technology to ensure installation position deviation is controlled within ±2mm; for large or irregularly shaped components, dedicated lifting brackets and fixing nodes must be designed to avoid deformation during lifting. In the Shanghai New World Nanjing East Road Century Plaza renovation project, for the 12m² super-large UHPC light-transmitting panel, Qinglong customized dedicated lifting equipment and brackets to ensure smooth lifting without deformation; during installation, component connection gaps must be controlled and filled with dedicated sealing materials to ensure waterproofing and aesthetics; after installation, an overall inspection must be conducted to ensure component flatness and verticality meet design requirements.

Environmental adaptation requires flexible adjustment to cope with different construction conditions. UHPC construction has certain requirements for ambient temperature and humidity, with a suitable construction temperature of 5-35℃; if the temperature is too low, insulation measures must be taken, and if too high, ventilation and cooling must be strengthened; rainy-day construction requires rain protection measures to prevent rain from washing away mixtures that have not yet set; in coastal areas or corrosive environments, surface protection treatment must be carried out promptly after construction to enhance durability. In the Hainan Poly Peninsula No. 1 project, Qinglong adjusted the curing plan and construction schedule for the high-temperature, high-humidity environment, choosing to construct during the cooler early morning and evening hours, ensuring that construction quality was not affected by environmental conditions.

Safety regulations must be strictly implemented to ensure construction safety. UHPC components are mostly large or heavy, so during lifting, the safety of lifting equipment and ropes must be checked, warning zones must be set up, and unrelated personnel must be kept out; workers at heights must wear safety protection equipment and safety protection facilities must be erected; the construction site must be equipped with fire-fighting equipment and first aid supplies, and emergency plans must be formulated. Qinglong has established a comprehensive safety production management system, with a dedicated safety officer assigned to every project to supervise construction safety throughout the process—no major safety accidents have occurred in 28 years.

Quality acceptance must be comprehensive and meticulous to ensure the project meets standards. After construction, appearance quality and performance testing must be carried out. In terms of appearance, there should be no defects such as cracks, honeycombing, or pitted surfaces, and surface flatness and verticality should meet requirements; in terms of performance, indicators such as compressive strength, flexural strength, and durability must be tested to ensure compliance with design standards and industry specifications. Qinglong has a well-equipped testing laboratory capable of comprehensive testing of finished products, and also cooperates with third-party testing agencies for sampling inspections to ensure project quality meets standards. In the Shenzhen Pingshan High-tech Zone Comprehensive Service Center project, Qinglong's UHPC construction quality passed strict acceptance, helping the project win the Luban Award.

In summary, UHPC construction requires attention to eight key points: pre-construction preparation, mixing process, pouring operations, curing, installation precision, environmental adaptation, safety regulations, and quality acceptance. As an industry leader integrating full-chain services of detailed design, manufacturing, construction and installation, and after-sales maintenance, Qinglong has always upheld the mission of "creating aesthetically beautiful architecture", relying on professional technology, advanced equipment, an experienced team, and a sound management system to ensure the construction quality of every UHPC project. Whether it is a public art project with complex shapes or a large-scale exterior wall installation project, Qinglong can precisely control construction details and deliver high-quality architectural works to customers.