Chemical anchoring is a method to fasten rebars or threaded bars to concrete and similar base structures. Chemical anchoring provides more flexibility than mechanical anchoring.

A mechanical anchor (set anchor/wedge anchor/drop-in anchor) is inserted in the concrete and expands upon tightening. This expansion causes the anchor to grip the wall of the hole and provide an extremely strong holding force. Whilst being a very popular and economical option, there are, however, some limitations.(1)

Chemical Anchoring Example in Sri Lanka


Chemical Anchoring Advantages

With chemical anchoring, a resin is injected into the hole before insertion of the stud. With this, the chemical naturally fills in all irregularities and therefore makes the hole airtight and waterproof, with 100% adhesion.

And with mechanical anchors, each predetermined size—length (embedment) and diameter—has its load capacity limits. Chemical anchors have virtually unlimited embedment depth, so you can embed any length of the threaded bar into the hole to increase the load capacity (There are some limitations). And if you choose to use a larger-diameter hole with a thicker rod, you increase load capacity again.

Chemical Type Anchors in Sri Lanka

Non-expanding nature

Chemical anchors are also called chemical studs. The chemical studs can also be placed towards the edge of concrete substrates and through masonry blocks. The non-expanding nature of a chemically-held rod drastically reduces the chance of the surrounding concrete cracking. This is very good for securing railings close to the edge, or concrete stairs, and similar applications.

Position can be adjusted

Finally, chemical anchoring gives you the opportunity to make slight adjustments to the stud’s alignment during the chemicals' open working time, whereas a mechanical anchor needs a hole to be drilled millimeter-perfect every time to correct depth and angle, and if it isn’t, it cannot be used.


Disadvantages of Chemical Anchors

Chemical anchors are more complicated to install, and incorrect installation habits can jeopardize the anchor’s capacity. Following correct installation methods are critical. They may also be considered more expensive than mechanical anchors. Chemical and mechanical fasteners are often used for very different things, especially when satisfying engineers’ requirements.


Hole diameter and Embedment Depth for the Chemical Anchoring

One of the chemical anchoring applications is to provide starter bars for lintels, stiffener beams, and columns or beams where a strong anchorage of bars is to be given. The epoxy adhesive anchoring system is used widely for anchoring purposes. Drill bit size is depending on the rebar going to be anchored to the structure. After drilling the hole, the hole should be cleaned with a hole cleaning pump to remove all dust inside. Then the resin should be injected with an injection anchor dispenser and pushed the bar inside while giving a torque to expel the excess resin out before hardening of the resin. The loading capacity can be increased by extending the embedment depth of the bar. The following table shows the required hole diameter and embedment depth for the anchoring rebar size. (2)

(Always consult the supplier for further information related to a particular chemical anchoring product.)

Chemical Anchoring Depth Chart


Chemical Anchoring Sinhala Article

හඳුන්වාදීම - කෙමිකල් ඇන්කරින් කියන්නේ මොකද්ද?

කොන්ක්‍රීට් එකට කම්බි (රීබාර්) හයිකරන එකට තමා කෙමිකල් ඇන්කරින් කරනවා කියන්නේ. දැනට තියෙන කොන්ක්‍රීට් එකක සිදුරක් විදලා කෙමිකල් දාලා රීබාර් කම්බියක් හයිකරන එකට තමා කෙමිකල් ඇන්කරින් කරනවා කියන්නේ. (3)

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References

1 What is a Chemical Anchor? (n.d.). Allfasteners. Retrieved Jun 01, 2021, from https://www.allfasteners.com.au/news-articles/what-is-a-chemical-anchor

2 Diya Chemical Anchoring System – Epoxy Adhesives (2019, September 23). Basic Civil Engineering. Retrieved Jun 01, 2021, from https://basiccivilengineering.com/2019/09/chemical-anchoring-system-epoxy-adhesives.html

3 Dias, P. Chemical Anchoring in Sri Lanka (2021, April 18). Praveen’s Blog. Retrieved Jun 01, 2021, from https://praveendias.blog/chemical-anchoring-sri-lanka/index.html