What Are the Key Steps in the Factory Precasting Stage of UHPC Curtain Wall Panel Production? Precasting Process and Key Quality Control Points Explained

Factory prefabrication of UHPC curtain wall panels is the core process for ensuring product quality. It requires standardized procedures and strict quality control to ensure that component precision, strength, and appearance meet design requirements. Defining the key production steps and quality control points is essential for efficient industrialized production. Drawing on 28 years of prefabrication experience, Qinglong analyzes the core processes and practical solutions.

1. Design Development and Mold Preparation: The Foundation of Prefabrication

Design development and mold preparation are the first steps of factory prefabrication and directly affect subsequent production quality. Design development uses BIM technology and parametric design to optimize panel dimensions, joint details, and reinforcement layout, ensuring manufacturability. In the Shanghai Century Plaza UHPC curtain wall project, Qinglong solved the prefabrication challenge of oversized 12㎡ panels through BIM-based design development; molds are selected as high-precision steel or GRP molds. Steel molds are CNC-machined with dimensional tolerances of ≤±0.5mm, and their surfaces are polished to ensure smoothness, while complex shaped components use custom GRP molds. Qinglong molds must pass trial assembly and precision inspection before use; a dedicated release agent is applied to the mold surface to ensure smooth demolding and prevent surface damage to components. The release agent must be applied evenly with full coverage, at a thickness controlled between 0.1-0.2mm.

2. Raw Material Proportioning and Mixing: Core Performance Control

Raw material proportioning and mixing must be precisely controlled to ensure stable UHPC performance. Raw materials include high-grade cement, silica fume, ultrafine quartz sand, and steel fibers, all subject to strict inspection upon delivery: cement strength grade ≥52.5, steel fiber tensile strength ≥2000MPa. Qinglong has established a raw material admission system, and substandard materials are strictly prohibited; mix proportions are precisely measured according to design requirements: the water-binder ratio is controlled between 0.22-0.25, and steel fiber content is ≥2% (by volume), using automated batching equipment with errors ≤±1%; mixing uses a twin-shaft forced mixer: first, aggregates and cementitious materials are dry-mixed for 2-3 minutes, then water and admixtures are added and wet-mixed for 3-5 minutes to ensure uniform steel fiber dispersion and prevent agglomeration. Qinglong monitors the mixing process in real time and retains test blocks from each batch for strength testing.

3. Casting, Forming, and Vibration: Surface and Compaction Control

Casting and vibration directly affect the compaction and surface quality of UHPC curtain wall panels. Low-drop, layered casting is adopted with a pour height ≤500mm, and each layer is vibrated promptly after casting to prevent air bubbles caused by free fall; vibration uses a high-frequency vibrating table (frequency 200-300Hz) or immersion vibrators, with vibration time controlled at 20-30 seconds per layer until the slurry surface shows laitance with no escaping bubbles. In the Yangshengtang Pharmaceutical Hangzhou Industrial Park project, Qinglong achieved UHPC density above 1.9g/cm³ through high-frequency vibration; shaped components or complex cavities use vacuum-assisted casting technology to remove internal air and improve compaction; after casting, surfaces are promptly troweled to remove laitance and air bubbles, ensuring a flat, smooth surface with flatness deviation ≤2mm/m.

4. Curing and Testing: Final Quality Assurance

Curing and testing are the final stages of prefabrication, ensuring components meet performance standards. Steam curing is adopted in three stages: preheating (heating rate ≤15℃/h), constant temperature (80-85℃, curing for 48 hours), and cooling (cooling rate ≤10℃/h). Qinglong's intelligent curing kilns precisely control temperature and humidity to ensure stable strength development; after curing, visual inspection is performed: surfaces must be free of cracks, bubbles, chipped edges and corners, and other defects, with dimensional deviation ≤±2mm; mechanical performance testing includes compressive strength (≥150MPa) and flexural strength (≥25MPa), with sampling tests for each batch, and only qualified products may leave the factory; finally, surface treatments such as stone-texture engraving and coating application enhance decorative effects. Qinglong uses five-axis engraving machines for high-precision texture replication to meet high-end project requirements. Through standardized prefabrication across the entire process and strict quality control, the factory pass rate of Qinglong UHPC curtain wall panels remains stable at over 99%.