Failure modes of chemical anchoring / Chemical Anchors and Injection Cartridge System Manufacturer

An installation test and pull off test before formal installation is recommended. Even though most of manufacturers provide testing report to support their chemical anchors. However, the conditions of the applications would not be exactly the same as the one they conducted in the test report. Thus, we always encourage customers to run a test and see if the result meets the requirement. If the result of pull off test is like any one of the 5 modes below, it means the anchoring failed. We should go back and check if there is any omission or incorrect action during the calculation and installation, then arrange a test again.  

A. Concrete cone failure

The steel anchor pulls out of the hole with a cone of concrete stuck to it. It usually happens with shallow embedment depth. If the embedment is not too deep, the top of concrete is quite weak and this type of failure will likely occur.  

B. Failure at the mortar/concrete boundary line

The steel anchor pulls out together with its adhesive casing. This failure is the separation at the boundary between the adhesive and concrete. It might cause by smooth wall of the hole. Roughening the wall of the hole by brushing it with a steel wire brush and then blowing out the dust will roughen the hole and improve the loads. If the dust is not cleaning well, it would like a layer of powder between the adhesive and concrete.

C. Failure at the mortar/steel boundary line

The steel anchor is pulled out of the adhesive casing. In the other word, the adhesive casing remains in the hole. It could be something wrong with the chemical anchor or the steel anchor is oily or has too much loose rust on the surface.

D. Mixed failure mode

The steel anchor is pulled out with the bottom part of the adhesive casing remaining in the hole. A combination of (b) and (c). This the worst failure mode.

E. Steel anchor failure

The steel anchor is snapped under tension load. It usually occurs for long embedment lengths. With this result, we get the idea that the bond strength of chemical anchor is very good.

Nowadays more and more install crews use epoxy solutions for the projects as epoxy anchoring is cheaper, easier and faster to install. But, if the epoxy anchors are not installed and cured properly, the epoxy will no longer maintain the required loading strength to ensure structural integrity of the anchor. The anchoring failure may result in collapse or partial collapse of the structure, endanger human life and/or cause considerable economic loss. It is very important for contractors, install crews and engineers to cooperate and design the best solution that meet industry requirement and install the chemical anchors correctly.