What to Note in UHPC Construction? Core Points of Four Key Stages

The success of UHPC construction stems from precise control of every detail; professional standards are the guarantee of quality.

The outstanding performance of ultra-high performance concrete (UHPC) can only be fully realized through standardized construction procedures. Any oversight in the construction process will not only affect the strength, durability, and decorative effect of the components, but may also leave potential safety hazards. Qinglong Group, with 28 years of UHPC construction experience and participation in formulating multiple industry standards, has drawn on the practice of numerous benchmark projects such as Shanghai Century Plaza and the Shanghai Astronomy Museum to summarize the core precautions for UHPC construction, covering the entire process from preliminary preparation to later-stage curing, safeguarding project quality.

I. Preliminary Construction Preparation: A Solid Foundation Ensures Trouble-Free Work

Preliminary preparation is the prerequisite for successful UHPC construction and requires comprehensive control across three dimensions: technology, materials, and equipment. For technical preparation, detailed design and construction plan compilation must be carried out, taking into account factors such as component type, dimensions, and installation position, to clarify mixing parameters, pouring techniques, curing plans, and installation procedures. Before each project starts, Qinglong Group organizes technical briefings for the design, production, and construction teams, and prepares detailed construction node drawings for complex components to ensure the construction process follows clear procedures.

Material preparation requires attention to storage and inspection. UHPC raw materials (quartz sand, special cement, steel fibers, admixtures, etc.) must be stored by category to avoid moisture, contamination, or mixed storage; steel fibers must be kept moisture-proof and rust-proof, and admixtures must be sealed for storage. All raw materials must be inspected before entering the site to ensure their performance indicators meet design requirements. Qinglong Group tests every batch of raw materials for indicators such as compressive strength, fineness, and mud content, and firmly refuses to use unqualified materials.

Equipment preparation must be debugged in advance. Mixing equipment should be a high-precision forced mixer to ensure uniform mixing of raw materials; before mixing, it must be cleaned and debugged, with the metering system calibrated to keep errors within ±0.1%. Pouring equipment should be selected according to component type: small pouring pumps for thin-walled components, and placing booms for large components. Curing equipment must be set up or debugged in advance to ensure precise temperature and humidity control. In addition, vibrating equipment, hoisting equipment, and testing tools must be prepared to ensure smooth construction.

II. Mixing and Pouring: Precise Control Is the Core

The mixing stage directly affects the workability and mechanical properties of UHPC and must strictly follow operating specifications. First is the feeding order of raw materials: materials should be fed in the order of "aggregate → cementitious materials → steel fibers → admixtures → water." Steel fibers must be added in a dispersed manner to avoid clumping. Qinglong Group's automated mixing equipment uses a special feeding device to ensure steel fibers are evenly distributed in the mix.

Mixing time must be strictly controlled, generally 3-5 minutes, with specific adjustments based on mixer type and mix condition. Too short a mixing time leads to uneven mixing and insufficient dispersion of steel fibers, affecting strength; too long a mixing time causes the mix temperature to rise, reduces workability, and may even cause segregation. During mixing, the condition of the mix must be observed to ensure uniform color, no lumps, and flowability that meets pouring requirements.

The pouring stage requires attention to continuity and vibration quality. Pouring should be carried out continuously without interruptions; if interrupted due to special circumstances, the interruption should not exceed 30 minutes, otherwise it must be treated as a construction joint. During vibration, appropriate vibrating equipment must be selected: high-frequency vibrators for thin-walled or complex-shaped components, with vibration time controlled at 10-20 seconds per point and spacing not exceeding 200mm, to ensure the mix is compactly filled without defects such as voids or honeycombs. In the pouring of the UHPC sculptures at the Shanghai Astronomy Museum, Qinglong Group adopted a layered vibration process with each layer no thicker than 300mm, ensuring thorough vibration without damaging the molds.

After pouring is complete, surface treatment must be carried out promptly: use a trowel to smooth and polish the surface, removing air bubbles and laitance. For decorative components, texture treatment must be performed according to design requirements to ensure the surface finish meets expectations.

III. Curing Process: Details Determine Final Performance

Curing is a critical stage for improving UHPC strength and durability, requiring strict control of temperature, humidity, and curing period. After pouring, moisture-retaining materials (such as geotextile or plastic film) should be applied before initial setting to prevent rapid water evaporation from causing surface cracking. After final setting, standard curing begins: the curing temperature should be maintained at 20-25℃, humidity no lower than 90%, and the curing period no less than 7 days; for components requiring high strength, the curing period should be extended to 14 days.

Qinglong Group adopts targeted curing plans based on different project environments: in hot, dry environments, automated curing sheds are built with misting systems for continuous moisture retention; in cold environments, steam curing is used, controlling the heating rate to no more than 10℃/hour and the cooling rate to no more than 5℃/hour to prevent component cracking caused by sudden temperature changes; for large or irregularly shaped components, wrapping with curing blankets is used to ensure uniform curing.

During curing, component strength must be tested regularly. Through tests on specimens cured under the same conditions, ensure that 7-day strength reaches over 70% of design strength and 28-day strength reaches over 100% of design strength. Hoisting or subsequent construction must not proceed until strength standards are met.

IV. Installation and Post-Installation Protection: Balancing Safety and Longevity

UHPC component installation requires precise positioning and secure fixing. Before installation, the installation base must be cleaned to ensure it is flat and clean, and lines must be snapped for positioning according to design requirements to clarify component installation positions and elevations. During installation, dedicated hoisting equipment is used to avoid collision damage to components; for large components or high-altitude installation, temporary supports must be set up to ensure a safe and stable installation process.

The fixing method should be selected according to component type and load conditions; common methods include dry hanging, bolt connection, and welding. In the Shenzhen Yirui Biotechnology Building project, Qinglong Group installed UHPC exterior wall panels using a multi-point hanging method, ensuring secure fixing and uniform load distribution. After installation, precision inspection is required: planar position error must not exceed 3mm, elevation error must not exceed 2mm, and verticality error must not exceed 1.5mm/m; any non-conformity must be adjusted promptly.

Post-installation protection is equally important. After installation, stains and dust on component surfaces must be cleaned promptly; for components with protection requirements, special protective agents can be applied to enhance stain and weathering resistance. Qinglong Group provides after-sales maintenance guidance for all UHPC projects, recommending regular inspections (1-2 times per year) so that issues such as cracks or looseness can be addressed promptly to ensure long-term safety in use.

The core of UHPC construction is "precision, standardization, and meticulousness," with strict technical requirements and operating specifications for every stage. As an industry-leading UHPC full-chain service enterprise, Qinglong Group always approaches every construction project with the attitude of "meticulousness and striving for excellence," ensuring construction quality meets standards and safety is under control through standardized processes, advanced technology, and professional teams. Following these construction points can fully leverage UHPC's performance advantages to create high-quality building projects that combine aesthetics, safety, and durability.