After testing literally thousands of post installed anchors and fasteners, we’ve unfortunately seen a few failures. Over the next couple of weeks, we’ll be sharing some of the knowledge we’ve gained over the years with you so you can make sure your anchors don’t fail.

This photo shows an anchor that was installed overhead into a cinder-concrete slab. You can see there is a screen tube that was used to allow the adhesive to expand into the void above the lower structural slab.

When an adhesive anchor is installed correctly, there are subtle changes in color to the freshly injected adhesive versus an adhesive that has had time to properly cure. This anchor was tested long after the required cure time, but appeared as if it was freshly installed.

The mixture was still wet and what portion of it that expanded through the screen tube did not harden. This anchor was pulled out of the drilled hole with little effort.

The typical cause for this kind of failure is when one simple step from the installation instructions is ignored or forgotten. Here, it appears that the first few trigger pulls of a new cartridge were not discarded.

If you do not discard the first few trigger pulls, the result is a mixture that does not contain the proper ratio of hardener to resin. But please do not blame the mixing nozzles. If you tried to mix the adhesive to the proper ratio by hand you would be much less successful. These mixing nozzles give you the precise ratio every time… as long as you discard the first few trigger pulls!

We at Clarke Engineering Services are all certified installers and special inspectors. We know what works. #AnchorWithConfidence

Happy Anchoring!

Brian Clarke, PE

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