Precast concrete components Prefabricated components are frequently used in prefabricated construction; however, if the quality of the precast concrete elements is inadequate, it can lead to the failure of the entire project. So, let’s now explore the requirements for manufacturing precast concrete components!

　　1. Mold

　　Precast concrete component molds shall possess adequate rigidity, strength, and stability to meet the dimensional accuracy requirements of the components. Each time before use, the molds must be thoroughly cleaned to ensure that no cement slurry or concrete residue remains. Steel is recommended as the material for manufacturing the molds, and the selected material must be accompanied by a certificate of quality or an inspection report. Except for the areas where finishing materials are to be applied, the formwork surface shall be evenly coated with a release agent.

　　2. Reinforcing Steel

　　Reinforcing steel bars must be accompanied by certificates of product conformity; the dimensions of finished rebar baskets must be accurate; and the bar specifications, quantities, placement, and tying methods must comply with relevant standards and design documentation. In addition, rebar shall undergo re-testing in accordance with applicable standards, and its quality must meet the requirements of current relevant standards. When placing rebar into formwork, it shall be laid flat and free from damage, with no oil stains, granular or flaky old rust on the surface. The rebar cage shall be supported and suspended as required to ensure that the concrete cover thickness is maintained at all locations.

　　3. Concrete

　　Concrete shall be produced using cement, aggregates (sand and gravel), admixtures, and mineral admixtures that have obtained certificates of conformity. The quality of cement, aggregates (sand and gravel), admixtures, blended materials, and water must comply with the provisions of current relevant standards. Re-testing shall be conducted in accordance with the relevant standards to verify the type, specification, and manufacturer of each material.

　　In accordance with the relevant provisions of the current national standard “Code for Mix Design of Ordinary Concrete” JGJ55, the measuring equipment for concrete raw materials shall operate reliably and provide accurate measurements, and the mix proportions shall be designed to meet the requirements for concrete strength grade, durability, and workability. Furthermore, metrological verification or calibration shall be carried out as prescribed.

　　4. Finish Machining

　　 Precast concrete components Facing materials such as stone and ceramic tiles shall be accompanied by certificates of product conformity or factory inspection reports. Prior to the installation of inlaid ceramic tiles, individual tiles shall first be cut and shaped in accordance with the component fabrication drawings to produce standardized tile units. Before stone tiles are laid in their formwork, a reinforcing treatment agent shall be applied to the back surface of the stone at least 24 hours in advance to enhance adhesion between the stone, ceramic tiles, and concrete, ensuring there are no voids. The type, specifications, and manufacturer of these materials must be clearly identified. The quality of stone, ceramic tiles, and other facing materials must comply with the provisions of current relevant standards. The number, location, and anti-corrosion treatment of hanging lugs and anchoring devices connecting the stone to the concrete must meet the design requirements. The surfaces of coated finishing components shall be smooth and even, with well-defined edges and grooves; any pores larger than 1 mm shall be filled and repaired.

　　5. Component Molding

　　Prior to concrete placement, concealed inspections must be carried out on precast concrete components; concrete may only be poured after compliance with relevant standards and design document requirements has been verified. The concrete formwork must be securely vibrated to ensure proper compaction. Vibrators shall not come into contact with steel structures, tiles, or embedded materials; any abnormalities must be promptly addressed through reinforcement and corrective measures. The concrete surface should be promptly leveled and finished with a clay trowel. The concrete pouring process shall be continuous, with simultaneous monitoring for deformation or displacement of formwork, doors and windows, and embedded materials, followed by a second finishing pass on the concrete surface. When the design drawings specify areas requiring a roughened finish, the following methods are generally employed.

　　1) Before the concrete has fully set, use a steel broom to roughen the surface of the member parallel to its face. The typical spacing is about 5 cm, with a roughening depth of 4–6 mm.

　　2) After the concrete has set, use a steel trowel to manually create a textured surface resembling a “flea” pattern. However, care must be taken not to apply excessive force, as this could lead to cracking and damage to the components.

　　3) Apply a retarder (also known as an exposure agent) to the steel formwork; after demolding, rinse off the coating agent with a high-pressure water jet to expose the aggregate, creating a natural rough surface—taking care, however, not to leave any residual coating agent.

　　6. Curing of Components

　　 Precast concrete components After concrete placement is completed, curing shall be carried out promptly. Either natural curing or steam curing may be used; when steam curing is employed, the following requirements shall be met.

　　1) The standing time after the completion of all concrete placement shall be no less than 2 hours;

　　2) The heating rate shall not exceed 15°C/h;

　　3) The temperature during constant-temperature treatment shall not exceed 55°C, and the duration of such treatment shall not exceed 3 hours.

　　4) The cooling rate shall not exceed 10°C/h;

　　5) During curing, pay attention to deformation of the window frame inserts.

　　The foregoing outlines the requirements for the fabrication of precast concrete components. For more information, please feel free to contact us at any time!