Hamilton Kent Blog

Get your box culverts ready for the job site

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Precast concrete box culverts are essentially the Lego of the construction world. You have a set number of pieces, and if they’re gasketed on arrival, there is no extra work except simply putting them together. They slide into place one-by-one and you’re good to go.

But because there is so little work required with precast on the job site, there are a few things that need to be taken care of before they even arrive. Check out our guide on box culvert planning, regulations, and testing methods in the blog below.

Why choose a box culvert?

On the job site, precast box culverts with pre-lubricated gaskets will save time. There is no need to install butyl, or apply lubricant in the field, and installation just means lowering a box into position and homing the joint carefully and evenly. Gaskets have lubricant sealed within the rolling tube, making it impervious to mud, dirt and debris, and they are made from a UV resistant rubber material for resistance to degradation due to exposure to UV and ozone for long periods.

Another advantage of using precast gasketed box culverts is scheduling and mapping your project with your precast supplier so everything arrives on time and where needed on the job site. If a line of culverts requires a bend, precasters are capable of creating skews and turns to keep your joint integrity high. This will prevent contractors from having to leave one side of the joint open, which increases the likelihood of a leak if the gap is more than ½” on any side.

Pressure ratings

Under ASTM C1677: Standard Specification for joints for concrete box, using rubber gaskets, ASTM international recommends that box culverts handle water pressures up to 5 psi.

When manufactured with single offset joints, fitted with the proper gasket and tested properly, your box culverts should easily handle this much pressure. If the culverts are exposed to a great deal of internal pressure or external vibration, some method of locking box sections together may be needed. This can be accomplished using cables run through each box to connect the culverts and post-tensioning, or with bolts placed in pre-formed pockets to lock the sections together.

Testing methods

ASTM recommends external joint tests specified under C1677 as well as ASTM C1619: Standard specification for elastrometric seals for joining concrete structures. These standards outline proof of design tests to complete before sending to a job site.

Joints can also be field tested using testing devices that isolate joints and test by vacuum or hydrostatic pressure. Such devices are manufactured by Cherne and Plug-It Products.

External joint test procedures

External tests create a pressurized pocket between the primary joint gasket and a secondary gasket which seals the outer portion of the joint between the face of the bell and end of the spigot. Once the gaskets are in place on the spigot, two access holes are drilled into the wall of the bell.

The exhaust port should be located at the highest vertical point on the box culvert. The inlet port placement is optional, however more specific instructions on where to place the inlet port if a pressure gauge is to be connected can be found here. These holes must align with the space that will be created between the two gaskets once the box sections are completely homed.

Epoxy should then be used to install and solidly anchor a galvanized steel nipple into each hole.

Once the box sections are homed together properly, it’s necessary to utilize a restraining method to hold the sections together. Without proper restraints, the potential is both there for false, negative test results, as well as failure of the joint because the sections pushed apart and opened the joint.

The space within the joint between the gaskets is filled with water and hydrostatic pressure is built up within the joint to the desired PSI level.

We have a complete, and detailed breakdown of external joint tests here as well as a video showing how they work here

For consultation on how to perform your own tests on your box culverts, and why they’re necessary, feel free to contact a Hamilton Kent rep here.