Failure modes of chemical anchoring2020/12/24
Chemical anchors provide strong bonding strength to connect objects into concrete and masonry. They are commonly used for all kinds of fixing projects from house repair to civil construction applications. To achieve a successful chemical anchoring and to ensure the reinforcement is strong enough, there are a few key factors to comply and not a single one can be omitted. For example, the diameter of the rod or rebar, the type of chemical anchor, the depth of the hole(embedment), the condition of the concrete (compressive strength), and the installation method. These key factors are influencing the strength of anchorage system and are critical in calculating the load capacity of chemical anchor.
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.
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Good Use Failure modes of chemical anchoring Introduction
Good Use Hardware Co., Ltd. is Taiwan supplier and manufacturer in producing chemical anchor in the industry. Good Use has been offering our customers high quality injection cartridge, chemical mortar, chemical anchor, anchor capsule, polyester resin,vinylester resin, epoxy acrylate resin, pure epoxy resin, styrene free resin, mixer nozzle, static mixer, plastic mixer, injection gun, caulking gun,dispenser,dispensing tool, dispensing gun, resin anchor since 1997. With both advanced technology and 20 years experience, Good Use always make sure to meet each customer's demand.