Precast Box Culverts: A Comprehensive Guide

You’ve probably encountered precast box culverts when driving through a subdivision, road project, or even out in the countryside. Precast box culverts are among the most widely used material for good reason, as they have a wide range of applications.


What are Precast Box Culverts?

Precast box culverts, or four-sided culverts, are made of concrete shaped like an enclosed rectangle. Generally, box culverts consist of a bottom slab, two wall elements, and a top slab.

Precast box culverts don’t need additional treatments to increase lifespan or functionality. The smooth interior finish of box culverts enables an optimal flow of water through the concrete structure. The best part is that precast box culverts don’t rust, unlike steel ones. They are the most economical way to redirect watercourses because they require little to no maintenance yet have a long lifespan.


Precast Box Culvert Specifications

Precast box culverts can measure up to a maximum of 2000mm in length but can still change due to the final mold configuration. Internal span sizes range from 1000mm to 6000mm, and internal heights from 500mm to 3600mm. Box culverts adhere to the following specifications when manufactured:

  • ASTM C1433
  • ASTM C1577
  • AASHTO M273
  • AASHTO M259

Manufacturing Methods

Precast box culverts can be made using two methods: dry-cast or wet-cast. Dry-cast or machine-made box culverts are typically cured in a kiln. The method leaves box culverts with a textured exterior. On the other hand, wet-cast box culverts use self-consolidating concrete and are usually used for sanitary applications.


Applications & Types

Precast box culverts can replace circular concrete pipes as they accommodate a higher water flow rate than pipes. Here are some of the many ways box culverts can be used:

  • Storm drainage
  • Road crossing
  • Short-span bridges
  • Tunnels
  • Rainwater harvesting
  • Railroads
  • Wildlife and stock crossings
  • Ducting


Also, precast box culverts can be categorized by size and orientation.

Most manufacturers create small to large sizes. Large sizes normally have a span of 1500mm and above. Inversely, small box culverts span 1200mm or less. Some manufacturers have a custom option, depending on the requirements of each client.

As for the orientation, precast box culverts are either inverted or crown-oriented. The inverted units are U-shaped troughs that come with or without lids. In contrast, crown-oriented box culverts have an n-shape.


Advantages of Precast Box Culverts

Precast Box Culverts are highly durable, especially for underground buildings. Culverts can be purchased in various sizes that can accommodate features, including animal ledges and twin-cell configuration units. A culvert’s bottom slab lessens soil pressure and can be used on top of a weak foundation. Installing this doesn’t require a heavy workforce, significantly reducing costs.


Building with Precast Box Culverts

Precast concrete box culverts are the best choice for most civil engineering and construction applications for their versatility. Contractors prefer to use box culverts as it effectively handles water flow. Box culverts are stronger and easier to construct and install when compared to other Culverts. The demonstrated durability, performance, and good service life prove its worth.



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