Construction Method of Prefabricated Concrete Beams for Houses
The construction method of prefabricated concrete beams for houses mainly includes key steps such as production method, formwork fabrication, steel bar processing and installation, concrete pouring, curing, prestressing treatment, duct grouting, and beam removal and storage.
In terms of production method, the production of prefabricated beams adopts a standardized assembly-line operation, covering major processes such as formwork fabrication, steel bar processing and installation, concrete pouring, and curing to ensure efficient and standardized production.
During the formwork fabrication stage, steel formworks are commonly used, and some beam yards may employ stainless steel plate bottom formworks. The camber is set according to design requirements to ensure the shape and dimensional accuracy of the prefabricated beams.
When processing and installing steel bars, the bottom and web steel bars are welded and formed on a binding jig, and the web corrugated pipes are also bound and welded with the bottom and web steel bars during this process. After that, the bottom and web steel bars are hoisted onto the box girder formwork where the side formworks have been installed, and high-strength mortar blocks are used to control the concrete cover of the steel bars, ensuring their accurate position in the concrete and enabling them to exert their proper mechanical properties.
During concrete pouring, gantry cranes are used for operation. The pouring is carried out from one end to the other, with a layer thickness of no more than 30 cm. The bottom and web are vibrated using external vibrators, while the top plate and the parts above the web corrugated pipes are vibrated using immersion vibrators to ensure the compactness of the concrete and avoid quality issues such as honeycombs and pitted surfaces.
For curing, automatic sprinkler curing must be carried out promptly after the concrete pouring is completed, with a curing period of no less than 7 days. In addition, curing methods such as steam, hot formwork, and solar energy can also be adopted, and an appropriate curing method should be selected according to different environmental conditions and the requirements of the prefabricated beams to ensure the normal growth of concrete strength.
During prestressing treatment, the prestressed steel strands can only be tensioned after the strength of the concrete test cubes under the same conditions reaches at least 75% of the designed concrete strength grade and the concrete age is no less than 7 days, and with the approval of the supervisor. The prestressed steel strands of the prefabricated beams are tensioned using intelligent tensioning equipment, and symmetric tensioning at both ends is carried out strictly according to the designed tensioning sequence. After tensioning, anchor sealing treatment is performed.
In the stage of duct grouting and beam removal and storage, the grout for duct grouting is prepared using special grouting materials or grouting agents, and end pouring is carried out. The beams can only be moved when the strength of the cement grout in the duct reaches at least 30 MPa. The components should be stacked according to the hoisting and installation sequence, with no more than two layers of stored beams, and the storage time should not exceed 3 months.
