A concrete placing boom is a critical piece of terminal equipment in concrete pumping operations. It is primarily used to receive concrete from a pump and deliver it precisely to the designated construction area, distributing it evenly within formwork or structural components. By extending the reach of the concrete pump, these units minimize the need for manual handling or secondary transport, thereby enhancing the efficiency of concrete placement. They are widely employed in the construction of building floor slabs, bridges, tunnels, and various other concrete structures.

　　I. Main Structure and Operational Characteristics

　　Concrete placing booms typically consist of a slewing mechanism, a placing boom (arm assembly), a delivery pipeline, a support structure, and an operating system. Through the coordinated movement of the slewing frame, the delivery pipeline can be maneuvered flexibly within a specific radius, allowing it to reach various pouring locations.

　　Depending on the construction environment, site conditions, and specific operational requirements, concrete placing booms can be designed in various configurations. Common types include internal-climbing, mobile (wheeled/tracked), barge-mounted, and manual models—collectively forming the comprehensive HG series of concrete placing booms.

　　Different models are suited to specific construction scenarios. For instance, internal-climbing units are ideal for high-rise building construction, as they can be raised floor-by-floor alongside the rising structure. Mobile units offer high maneuverability, making them suitable for sites where pouring locations change frequently. Barge-mounted units are designed for marine or water-based projects, while manual units feature a simpler design and are best suited for applications with fixed pouring ranges and operational requirements.

　　Selecting the appropriate type of placing boom can optimize the organization of concrete delivery and placement, ultimately boosting construction efficiency.

　　II. Vacuum Dewatering in Concrete Construction

　　In certain concrete construction projects and the production of precast components, vacuum dewatering technology can be utilized to improve the density and molding quality of the concrete.

　　Vacuum dewatering employs a vacuum pump to generate negative pressure. Through a filtration layer or specialized equipment, excess water and entrapped air are extracted from the concrete. This process effectively lowers the actual water-cement ratio, resulting in a denser concrete structure. Depending on the placement of the dewatering equipment and the construction method, the process is primarily categorized into the following four types:

　　1. Top-Surface Dewatering

　　In top-surface dewatering, rigid suction pads or flexible, rollable suction mats are placed onto the surface of freshly poured concrete. A vacuum pump is then used to draw out excess water from within the concrete through a filtration layer.

　　This method is suitable for cement concrete pavements, airport runways, cast-in-place concrete floor slabs, ground-level construction, and the production of precast components with uniform cross-sections. Properly controlling the duration of the dewatering process helps improve the surface quality and workability of the concrete.

　　2. Bottom-Surface Dewatering

　　Bottom-surface dewatering typically employs rigid vacuum-chamber molds. The vacuum dewatering equipment is positioned beneath the concrete component, allowing for suction to be applied from the underside.

　　This approach is designed for precast concrete components with varying cross-sections, such as trough-shaped or ribbed elements. By incorporating a vacuum chamber into the base of the mold, excess water can be extracted during the concrete forming process, meeting the specific production requirements for such components.

　　3. Side-Surface Dewatering

　　Side-surface dewatering is primarily used for cast-in-place concrete structures with inclined or vertical surfaces, such as dams, columns, and walls.

　　During construction, porous pipes equipped with filtration layers are embedded within the concrete and connected to a vacuum pipeline system. A vacuum pump creates negative pressure, drawing excess water from the concrete toward the porous pipes, from which it is then discharged. These porous pipes are typically designed with a slight taper, allowing them to be withdrawn once the vacuum treatment is complete.

　　This method is well-suited for the internal dewatering of certain large-scale or specialized concrete structures.

　　4. Embedded Dewatering

　　In embedded dewatering, three-dimensional filters—constructed from porous, fine-aggregate concrete—are installed within the formwork prior to the concrete pour and connected to a vacuum pipeline system.

　　Once the concrete has been poured, a vacuum system is used to extract excess water. Unlike the removable porous pipes mentioned previously, these embedded filters remain inside the concrete structure after the dewatering process is finished and do not need to be removed.

　　This method is applicable to specific types of structures or concrete projects that require internal dewatering; its implementation should be determined based on the design of the component and the specific construction techniques employed.

       III. Rational Selection of Equipment and Construction Methods

　　Concrete placing booms are primarily used to handle the final stage of concrete transport and distribution, whereas vacuum dewatering serves as an auxiliary treatment process during the concrete forming stage; each addresses a different phase of construction. In practical engineering, the selection of appropriate placing equipment should be based on factors such as the building structure, the area to be poured, the required placing radius, available construction space, and the specific properties of the concrete. Furthermore, the decision to employ vacuum dewatering technology should be made in light of the project's quality requirements.

　　By rationally configuring placing booms and other construction equipment—and by optimizing the processes for concrete transport, pouring, and forming—it is possible to enhance construction efficiency and improve the quality of the finished concrete elements.