CROSS Safety Report
Installation of epoxy resin adhesive for reinforcing bar anchors
The reporter encountered an unsafe procedure for the installation of epoxy resin fixed reinforcement bars. The correct procedure involves the insertion of epoxy resin to a pre-determined depth within a pre-drilled hole followed by the insertion of the reinforcement bars to the correct depth. In the case of the unsafe procedure, the bars were inserted first and then a small amount of epoxy resin had been placed around the top of the hole. This gave the appearance of a correctly installed connection. This is a serious concern as the connections would have almost no structural strength and could fail catastrophically.
Key Learning Outcomes
For civil and structural engineers:
- Encourage designers to carry out periodic inspections on-site to verify and validate the quality of site work, including use of simple pull-out tests
- Consider on-site checks for depths and diameters of holes, techniques for clean-out, dryness of holes, techniques for inserting rebars, and types of adhesive
- Consider specifying installation of anchors by certified entities only, with specified hold points, recording measures and load-testing of independently selected anchors
For building authorities:
- Consider the introduction of mandatory certification of installers
- Ensure installation is carried out by trained, experienced installers familiar with the product and method of installation
- Refer to the Australian Engineered Fasteners and Anchors Council (AEFAC) program for certification of installers
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The reporter, a structural engineer working in a design consultancy, encountered two situations on separate sites where reinforcement bars had been fixed by means of epoxy resin adhesive using a potentially unsafe procedure.
The correct procedure involves the insertion of epoxy resin to full depth within a pre-drilled hole (of specified depth), followed by the insertion of reinforcement bars to the correct depth as required in the specification. In the case of the unsafe procedure, the bars were inserted first (into an empty hole) and then a small amount of epoxy resin had been placed around the top of the hole which gave the appearance of a correctly installed connection.
Site engineers from the consulting firm had noticed the bars extended out from the concrete further than was expected. When pulled by hand the bars came loose. The joints were severely under capacity and would have the potential to fail in service if not rectified. This raised a serious concern as the connections would have almost no structural strength and could fail catastrophically if not identified and rectified before the casting of wet concrete.
In the reporter's opinion, these instances could have been deliberate attempts to save time and cost on site. They highlight that inspection after the fact is not possible as everything becomes buried in concrete and, if the bars had not been noticed and pulled out by the site engineers, the underlying defects would not have been detected.
The reporter notes that AS5216:2021 - Design of post-installed and cast-in fastenings in concrete has been recently introduced to include design of this type of connection. However, it does not specify any requirements for site inspection, testing, and quality control. The reporter believes this Australian Standard should be amended to include installation requirements similar to procedures for welding, such as supervision, inspection and testing.
Also, the reporter considers there should be an education program about the dangers of not installing these bars correctly, so that engineers and builders can put adequate inspection and testing regimes in place.
Expert Panel Comments
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Not only does this report illustrate, yet again, the deficiencies in quality control in parts of the building and construction industry, but it also introduces the unfortunate issue of potentially reckless behaviour.
While the responsibility for construction compliance clearly lies with the contractor and the installer (and not the design consultant), it nevertheless highlights the need for quality assurance compliance such as the attendance by designers to carry out periodic inspections to provide an indication of the contractor’s quality, where observed, and of the construction progress. It may also serve as an indicator of the need for increased independent verification and validation of the quality of site work.
With respect to the installation of post-fixed anchors and reinforcing bars, critical considerations include depth and diameter of holes, technique for clean-out, dryness of holes, technique for inserting rebars, and type of adhesive. Installation should always be carried out by trained, experienced installers familiar with the product and method of installation. The Australian Engineered Fasteners and Anchors Council (AEFAC) conducts a program for certification of installers, and it may be that building authorities should consider making this mandatory for installers in the industry.
In general, the designer should consider specifying installation of anchors by certified entities only; and should specify hold points, recording measures and load-testing of independently selected samples for items when:
- there is a critical stage of load-transfer that relies heavily on one or more key details
- integrity of an individual connection is critical – i.e. load redistribution and/or secondary pathways are not possible
- there may be deficiencies in procedures of quality control for highly critical elements of load transfer
- a risk of construction non-compliance is suspected.
In addition, where reckless activity is suspected, the relevant parties to the Contract should consider whether they should report it to the relevant statutory authorities (e.g. SafeWork NSW, WorkSafe QLD/VIC, WorkSafe NZ etc) for further action, and also to Engineers Australia for consideration as a possible breach of professional ethics.
There have been several previous CROSS reports related to the incorrect installation of post-drilled resin fixings that have led to structural collapse. This led to the publication of CROSS Alert “Tension systems and post-drilled resin fixings” in March 2014. Since that time searching the CROSS database for resin fixings produces several more reports. Clearly, this is a continuing problem.
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