What Are the UHPC Pouring Methods? Suitable Choices for Different Scenarios and Key Practical Points

There is no "optimal solution" for UHPC casting methods, only the "best fit"—choosing the right method is essential to ensure quality and efficiency.

Casting UHPC is the critical step of transforming the mix into formed components. Different component types, levels of design complexity, and dimensions require matching casting methods. Selecting the appropriate casting method ensures forming quality, improves construction efficiency, and reduces costs. Qinglong Group, with 28 years of UHPC construction experience and numerous complex projects completed, has summarized the mainstream UHPC casting methods, detailing their applicable scenarios and practical key points to serve as a reference for project construction.

1. Mold-Press Casting: An Efficient Choice for Standardized Components

Mold-press casting is one of the most commonly used UHPC casting methods, suitable for standardized, mass-produced flat panels, simple linear components, and the like, such as UHPC exterior wall panels, decorative moldings, and landscape benches. This method forms components through mold pressing, offering advantages such as high production efficiency, high dimensional accuracy, and uniform surface texture.

Regarding practical key points, first prepare high-precision steel or GRP molds. The mold surface must be smooth and even, coated with a specialized release agent to ensure smooth demolding after forming. Pour the well-mixed UHPC mix into the mold, with the amount slightly above the mold edge, then apply pressure through a press machine or vibrating table—pressure is typically 0.5-1.5MPa with a vibration frequency of 20-50Hz—to ensure the mix fills densely and air bubbles are expelled.

When producing UHPC flat panel components for the Shenzhen Yirui Biotechnology Building, Qinglong Group adopted mold-press casting, achieving mass production through an automated mold-pressing line with a daily output of over 500 square meters, dimensional accuracy controlled within ±1mm, and surface flatness deviation of no more than 2mm. This method's advantages are high production efficiency and relatively low cost, making it suitable for large-scale standardized production, but it adapts poorly to components with complex designs.

2. Spray Casting: A Suitable Solution for Thin-Walled and Complex Designs

Spray casting is suitable for thin-walled components, complex curved components, hollowed-out components, and the like, such as UHPC hollowed-out exterior wall panels, thin decorative components, and sculptural shapes. This method sprays the UHPC mix at high speed onto molds or work surfaces via a spraying machine, offering advantages such as flexible forming, adaptability to complex shapes, and no need for vibration.

During practice, attention must be paid to spray parameter control: spray pressure is typically 0.3-0.6MPa, spray distance maintained at 300-500mm, and spray angle at 45°-90°, ensuring the mix uniformly covers the mold with consistent thickness. Spraying must be done in layers, with each layer controlled at 10-20mm thickness; spray the next layer only after the previous layer has initially set to avoid delamination between layers.

In the UHPC hollowed-out exterior wall panel construction for the Ouargla Hotel in Algeria, Qinglong Group adopted spray casting, successfully forming components with an openwork ratio exceeding 50%, a thickness of only 50mm, and a smooth, fine surface. The key to this method lies in controlling spray pressure and speed to avoid mix rebound or accumulation, while also ensuring the mold is sturdy enough to withstand spray pressure. However, spray casting has relatively low production efficiency and is suited to small-batch production of complex-shaped components.

3. Pump Casting: An Efficient Solution for Large and Elevated Components

Pump casting is suitable for large components, elevated components, and long-distance casting projects, such as large UHPC sculptures, elevated exterior wall panels, and bridge decorative components. This method transports the UHPC mix to the casting location via a concrete pump, offering advantages such as wide casting range, high efficiency, and no need for manual handling.

Before practice, inspect the pumping equipment to ensure pipelines are unobstructed and well-sealed; coat the inner pipe walls with lubricant to reduce mix resistance. The UHPC mix's flowability must meet pumping requirements, with slump typically controlled at 200-250mm; if necessary, adjust admixture dosage to optimize flowability. During pumping, control the pumping speed to avoid pipeline blockage caused by excessive speed, and assign dedicated personnel to observe the casting, ensuring the mix fills densely.

In the UHPC sculpture project for the Shanghai Astronomy Museum, Qinglong Group adopted pump casting, transporting the mix to elevated molds over 3 meters high and achieving integral casting of the large sculpture, which not only improved construction efficiency but also ensured the component's structural integrity. This method's advantage is its suitability for long-distance and elevated casting scenarios, but it places high demands on mix flowability, requiring strict mix proportion control to avoid pipeline blockage.

4. Vacuum-Assisted Casting: A Quality Choice for High Precision and High Density

Vacuum-assisted casting is suitable for components with extremely high requirements for density, strength, and surface quality, such as high-precision decorative components, load-bearing components, and components used in special environments. This method uses vacuum equipment to expel air and excess moisture from the mold, improving the mix's density and strength while reducing air bubbles and pores.

During practice, lay vacuum filter cloth and vacuum pipelines inside the mold, seal the mold, then start the vacuum equipment with vacuum level controlled at -0.06 to -0.08MPa, maintaining the vacuum state for 5-10 minutes before casting. Keep the vacuum constant during casting until the mix fills the mold; after casting, maintain the vacuum for another 10-15 minutes to ensure air bubbles are fully expelled.

When producing UHPC wood-grain translucent panels for Shanghai Century Plaza, Qinglong Group adopted vacuum-assisted casting, achieving component density above 2.5g/cm³, with no obvious surface air bubbles and uniform, consistent light transmission. This method can significantly improve components' mechanical properties and surface quality, but it requires substantial equipment investment, involves a complex construction process, and has relatively high costs, making it suitable for projects with extremely high quality requirements.

The UHPC casting method must be selected comprehensively based on factors such as component type, design complexity, dimensions, and construction environment. Mold-press casting suits standardized mass production, spray casting suits complex-shaped components, pump casting suits large elevated projects, and vacuum-assisted casting suits high-quality components. As an industry-leading UHPC full-chain service enterprise, Qinglong Group can develop customized casting solutions according to different project needs, ensuring component forming quality through professional equipment and teams. Choosing the right casting method fully leverages UHPC's material advantages to create architectural components that are both aesthetic and practical.