What Should Be Noted in UHPC Construction? Key Whole-Process Control Points Summarized by Industry Benchmarks

The success or failure of UHPC construction lies in the precise control of every detail—from early preparation to later curing, nothing can be overlooked. As an industry benchmark that participated in formulating the standard for Ultra-High Performance Concrete (UHPC) Exterior Wall Panels, Qinglong Group, with 28 years of UHPC construction experience, knows well that UHPC construction is a systematic project, where negligence in any step may lead to problems such as component cracking, insufficient strength, and installation deviation, affecting the overall quality and service life of the project. In response to the construction points of greatest concern to designers, owners, and construction teams, Qinglong Group has sorted out key control points across the entire process, providing professional guidance for smooth project advancement.

#I. Pre-Construction Preparation: Technical Disclosure and Site Adaptation Are the Foundation Adequate preparation before construction is the prerequisite for successful UHPC construction, with the core lying in technical disclosure and site condition adaptation. Before construction, the Qinglong team organizes technical disclosure among the three parties—design, production, and construction—focusing on key information such as component dimensional tolerances (allowable deviation ≤±3mm), installation node requirements, and performance indicator standards (compressive strength ≥120MPa, flexural strength ≥20MPa). Meanwhile, BIM models are used to simulate the entire construction process, optimizing component splitting and hoisting paths to avoid rework later. Site condition adaptation is equally critical: the flatness of the construction site (error ≤±5mm), the load-bearing capacity of hoisting equipment (≥1.5 times the component weight), and a stable water and power supply (voltage fluctuation ≤±10%) must all be ensured; for outdoor construction, rain and wind protection measures (such as erecting temporary protective shelters) must be planned in advance to prevent environmental factors from affecting construction quality. In the Ouargla Hotel project in Algeria, through detailed preliminary surveys, the Qinglong team adjusted construction schedules under the local high-temperature environment (avoiding the midday heat), ensuring the construction results of the UHPC hollow-out panels.

#II. Mixing: Precise Control Ensures Material Performance Mixing is the core step of UHPC construction, directly determining the homogeneity and final performance of the material, and requires strict control of three key points. First, precise measurement of raw materials: Qinglong uses a fully automatic metering system, with measurement errors for cement, aggregates, steel fibers, and admixtures of ≤±1%. In particular, the steel fiber dosage must strictly follow the mix ratio (volume fraction 2%-3%) to avoid reduced strength due to insufficient dosage. Second, a scientific mixing sequence: follow the process of "aggregates + cement + reactive powders → dry mix for 2 minutes → add water + admixtures → wet mix for 3-5 minutes → add steel fibers → mix for 2 minutes" to ensure steel fibers are evenly dispersed without agglomeration. Third, adapted mixing parameters: adjust the mixing time according to ambient temperature (extend by 1-2 minutes at low temperatures) and control the discharge temperature of the mixture (15-25°C); temperatures either too high or too low will affect setting time and strength development. Qinglong's production base is equipped with an intelligent mixing monitoring system that monitors parameters such as temperature, rotation speed, and time in real time during mixing, ensuring consistent performance of every batch of mixture.

#III. Pouring Operations: Standardized Operations Ensure Forming Quality The standardization of pouring operations directly affects the forming quality of UHPC components, requiring focused control of pouring speed, vibration methods, and mold treatment. Pouring speed should be controlled at 0.3-0.5m/h, with layered pouring (each layer ≤300mm thick) to avoid air bubble retention and layer segregation caused by pouring too fast; for components with complex shapes (such as the Shanghai Astronomy Museum sculpture), high-pressure grouting is used to ensure dense material filling. The vibration process requires high-frequency immersion vibrators (vibration frequency ≥12000 times/min), with vibration time controlled at 20-30 seconds per point and spacing ≤300mm, avoiding under-vibration or over-vibration—under-vibration creates voids, while over-vibration causes steel fibers to float. Mold treatment is equally critical: before pouring, a dedicated release agent must be applied inside the mold (avoid oil-based release agents), and the mold surface must be smooth with tight joints (gaps ≤0.5mm) to prevent slurry leakage; for oversized components (such as the 12m² UHPC wood-grain translucent panels), modular molds are used to enhance mold rigidity and prevent deformation during pouring.

#IV. Curing Stage: Scientific Management Achieves Target Strength Curing is a critical stage for UHPC strength development, requiring dedicated plans based on environmental conditions and component types. Qinglong's standard curing process is as follows: cover with moisture-retaining film within 12 hours after pouring (to prevent moisture evaporation), cure for 7 days at normal temperature (20±2°C), and demold after strength reaches 70% of the design value; after demolding, continue curing until 28 days to ensure strength meets design standards. For projects with tight schedules, steam curing (40-50°C, humidity ≥95%) can be adopted, reaching 80% of design strength after 3 days of curing, but the heating and cooling rates must be controlled (≤10°C/h) to avoid cracking caused by excessive temperature differences. In addition, outdoor curing requires protection from rain and sun to avoid sudden temperature rises and drops on component surfaces; for thin-walled components (thickness ≤50mm), the curing period should be extended to 14 days to ensure durability requirements are met. In the Yangshengtang Pharmaceutical Hangzhou Industrial Park project, Qinglong achieved a 28-day compressive strength of 150MPa for its UHPC exterior wall panels through scientific curing, far exceeding design requirements.

#V. Safety Protection: Maintaining the Construction Safety Bottom Line Throughout Safety protection during UHPC construction must not be overlooked, with particular focus on hoisting safety and operational protection. For hoisting, qualified lifting appliances must be selected (such as high-strength steel wire ropes and dedicated lifting clamps); lifting points must be set according to component load requirements (no fewer than 4 lifting points); components should be lifted slowly and moved smoothly during hoisting to avoid collision damage; workers at height must wear safety harnesses and helmets, and safety protection nets must be erected to ensure operational safety. Meanwhile, material transportation safety (avoiding mixture overflow and component collisions) and electrical safety (reliable equipment grounding and good wire insulation) must also be ensured. Qinglong has established a comprehensive construction safety management system, with dedicated safety officers assigned to each project and regular safety training and hazard inspections conducted, ensuring zero safety accidents throughout the entire construction process.

In summary, the core of UHPC construction lies in "precise control and scientific standardization"—from early preparation to later curing, every step must strictly follow technical standards and operating procedures. As an enterprise holding Grade II qualification for professional curtain wall engineering contracting, Qinglong Group, with 28 years of construction experience and a standardized process system, has successfully delivered thousands of UHPC projects, providing users with professional construction solutions. By seizing the key control points above, construction risks can be effectively mitigated, ensuring the quality, safety, and efficiency of UHPC projects.