What Are the Casting Methods for UHPC? Selecting Suitable Processes for Different Components

The pouring method for UHPC must be selected based on the component's shape, size, reinforcement conditions, and site conditions. The core principles are to ensure continuous pouring, avoid segregation, and guarantee compactness and uniformity of fiber distribution. The main pouring methods applied by Qinglong Group in various projects include the pump-lift method, the funnel-feed method, and the precast mold pouring method, each with its own specific application scenarios and technical key points. Choosing the correct pouring method is an important step in translating UHPC's excellent performance from the laboratory into actual engineering structures.

For large structures or parts that are difficult to pour directly into the mold (such as bridge piers and thin-walled hollow components), the pump-lift method is the first choice. A hydraulic piston pump suitable for high-viscosity materials with large aggregates (if any) should be selected; the pump line should be straight rather than bent, with a smooth inner wall. Before pumping, the line must be lubricated with mortar or cement slurry, and pumping should be carried out continuously to prevent blockage. During lift pouring, the process should start from the lowest point, allowing the UHPC to rise slowly and expel air. This method is especially suitable for vertical components.

For slabs, beams, small precast components, and the like, the funnel-feed method combined with auxiliary vibration is most commonly used. The UHPC is guided into the formwork through a funnel and tremie pipe, with the drop height controlled at no more than 1.5 meters to prevent segregation. For thin plates or complex cross-sections, multiple feeding points can be used to guide the UHPC to flow naturally and fill the mold cavity. High-frequency internal vibrators or attached vibrators can be used for auxiliary compaction, but the vibration points and duration must be strictly controlled to avoid over-vibration.

Under factory precast conditions, self-leveling pouring or shotcreting methods with higher production efficiency can be adopted. For flat plate components, the UHPC can be poured onto a flat casting bed, filling the mold by its self-leveling property, and then compacted by vibrating the casting bed. Shotcreting is mainly used for special shapes or strengthening projects, where fibers and slurry are conveyed separately to the nozzle, mixed, and then sprayed; this requires a high level of technical skill from operators. Whichever method is used, formwork wetting before pouring, environmental control during pouring (protection from wind and sun), and surface treatment after pouring must all be carried out in sync.