In the previous article, we talked about the structural design and installation of small box culverts. This article will guide you through the process of precast and quality control for small box culverts.

1. Precast Process

During the prefabrication stage of small box culverts, it is crucial to precisely design and carefully fabricate the formwork. High-quality materials should be selected to manufacture the formworks to ensure dimensional accuracy and structural rigidity so as to meet the shape and size requirements of the box culverts. The surface treatment of the formwork is of crucial importance. By applying a release agent, the surface of the box culverts after demoulding can be ensured to be smooth and clean, and at the same time, the adhesion between the concrete and the formworks can be reduced, facilitating the demoulding operation.

The work of cutting, bending, welding, and binding steel bars should be carried out meticulously in accordance with the design drawings, to ensure that the position, spacing, and thickness of the protective layer of the steel bar mesh strictly conform to the standard specifications. Advanced positioning devices and technical solutions should be utilized to accurately fix the steel bar skeleton within the templates, forming a stable and efficient force-bearing system that provides a solid foundation for the subsequent concrete pouring.

High-quality concrete should be mixed with a scientific and reasonable mix proportion, and it should be ensured that the concrete is evenly mixed and has a proper slump for easy construction. During the pouring process, the principle of "layered pouring and continuous vibration" should be followed. After each layer is poured, sufficient vibration should be conducted to eliminate air bubbles, ensuring proper adhesion between the concrete and steel bars and forming a solid, integral structure. In addition, close attention should be paid to the concrete curing measures to ensure that the strength development meets the expected requirements.

2. Quality Inspection and Control Methods for Precast Components

During the entire pre-cast process, high-precision measuring instruments should be used to regularly and strictly inspect and verify the dimensions of each part of the box culverts to ensure that the actual dimensions completely match the design drawings. Combined with modern three-dimensional scanning technology, a comprehensive scanning and comparison of the prefabricated box culverts should be conducted before and after pouring to promptly discover and correct potential dimensional deviation issues.

After the curing period of the concrete hardening is over, representative test blocks should be taken for compressive strength tests to verify that the actual bearing capacity of the precast box culverts meets the design requirements. For prestressed concrete box culverts, the effectiveness of prestressed tensioning and the density of grouting also need to be verified to ensure the effective application and transmission of prestress.

Attention should be paid to the quality management of the inner and outer surfaces of the prefabricated box culverts. Immediately after demoulding, it should be checked whether there are quality problems such as cracks, honeycombs, and pitted surfaces, and necessary repair measures should be taken according to the actual situation. At the same time, the concrete curing system should be strictly implemented, including moisture retention, heat preservation and other links, to ensure that both the apparent quality and the internal mechanical properties of the box culverts can meet the acceptance standards. 

3. Requirements for Transportation and Storage of Precast Components

During the hoisting and transportation of precast box culverts, special equipment and tools should be selected to avoid unnecessary collisions and abrasions during the lifting and loading and unloading processes. The positions of lifting points should be reasonably selected and appropriate lifting appliances should be used to ensure a smooth and safe lifting process. If necessary, flexible wrapping materials can be used to provide additional protection for vulnerable areas to reduce the risk of damage caused by transportation vibrations and other factors.

A site with solid foundation, good drainage conditions, and not easily affected by extreme climates should be selected as the temporary storage area for prefabricated box culverts. When stacking, the box culverts should be stacked according to the specified spacing and height to prevent mutual extrusion, deformation, or damage between the box culverts. Targeted protection measures should be taken for key parts such as reserved holes and joints. Furthermore, maintenance management work such as moisture prevention and sun protection, should be strengthened to ensure that the prefabricated box culverts maintain stable physical properties and durability during long-term storage.

To Wrap Up

This article details the precast and quality control of small box culverts. It includes precise formwork design, proper steel bar work, scientific concrete handling, and strict quality inspection like using instruments and 3D scanning. Also, it covers requirements for transportation and storage. To ensure high-quality box culverts, we must adhere to these procedures. Let's take action and apply these best practices in our projects. Only by doing so can we achieve excellent results and contribute to the durability and safety of infrastructure.