What Are Adhesive Anchors?
Adhesive anchors (otherwise known as chemical anchors) are a kind of concrete fastening held in place by a chemical adhesive, usually a two-part epoxy or a polyester-based adhesive. Adhesive anchors work well for many high-load applications, whether they’re structural or not, and a chemical anchor is often the best for structural integrity. The use of a specific type of chemical anchor may be part of the plans for a new building or renovation, particularly if it’s a civic infrastructure project.
Additionally, although they are often described as concrete fasteners or concrete anchoring systems, chemical anchors can be used in materials like masonry, block, brick, and even cracked concrete or concrete of unknown quality and strength.
How Do Adhesive Anchors Work?
Like mechanical anchors, adhesive anchors use rods or rebar to fix structural and nonstructural elements to a substrate. Chemical anchors are particularly useful for connecting concrete to concrete using rebar. The adhesives used in this kind of anchor provide more flexibility than mechanical anchors. They also avoid the pressure points created by most mechanical fastenings, with the strong adhesives used bearing most of the load put on the anchor once it is cured.Curing can take multiple days, with quick-curing epoxies hardening in about 24 hours and some other quick-cure adhesives becoming solid in as little as 7 hours.
To install a chemical anchor, you inject adhesive into the borehole you’ve created before inserting your stud or rebar. As the adhesive goes in as a paste it fills any gaps in the substrate, imperfections in your borehole, and any intentionally designed holes or thread in your stud. This molecular-level adhesion creates an extra level of strength, holding your stud or rebar in place.
Why Should You Use Chemical Anchors?
Chemical anchoring offers more flexibility than mechanical anchoring and creates a waterproof and chemical-exposure-proof seal around the metal components you use. This means that some adhesive anchors, specifically hybrid anchor systems and pure epoxy chemicals, can be installed in settings likely to experience adverse weather conditions, factory settings where chemical exposure is possible, and in some cases even underwater.As they have almost no maximum insertion depth (the stud will hold as long as the length of your stud is not more than 20x the width), chemical anchors are more suitable than mechanical for installing rebar and other long studs. The ability to post-install rebar to hold concrete to concrete is a huge plus point for chemical anchors.
When Should You Use Chemical Anchors?
Chemical anchors should be chosen over mechanical anchors in the following situations:- For cracked concrete
- For weak concrete
- When you don’t know the psi of concrete
- In unusual substrates like sandstone, limestone, or hollow walls
- When post-installing rebar
- When placing anchors at the edges of concrete
- When placing anchors close to one another
- When you need a perfect seal to protect your metal elements
- When specified on plans by engineers or architects, which will often be the case
Are Adhesive Anchors Better Than Mechanical Anchors?
Adhesive anchors have various advantages over mechanical anchors. For one, they can be placed in weak concrete, concrete of unknown strength, and many other substrates as there is much less chance of concrete cracking with adhesive than expanding anchors that exert pressure at specific points. If concrete is cracked, your adhesive will fill any cracks within the borehole.Chemical anchors can also be placed in masonry blocks, which mechanical anchors don’t perform well in, and close to the edges of concrete structures.
They are particularly useful for placing railings as well as installing banisters on concrete sets of stairs. Adhesive anchors work better than mechanical anchors when grouped for the same reason – the adhesive itself bears the load placed on the anchor system, putting minimal pressure on the substrate and the stud.
Finally, when you drill a hole for a chemical anchor, it doesn’t have to be perfect. Your adhesive will fill in any inconsistencies. It will also fill the additional space if the hole is larger than would be ideal for a specific stud, although there are, of course, limits to this, and you risk wasting adhesive if you drill a hole far too deep or wide.
For mechanical anchors, on the other hand, you have to drill a millimeter-perfect hole that’s just a little larger than your mechanical peg. The exact size of the hole needed for a mechanical anchor depends on the type of mechanical anchor you’re using.
While it’s true that adhesive anchor installation has to be carried out carefully, it’s not a difficult process. The most important things to remember are:
The time it takes for chemical anchors to set can also be an issue on some job sites. If it’s cold or, in some cases, very warm, the setting may take longer than it should or not happen at all. That being said, the extra time can be helpful under normal curing conditions, as you can continue to make small adjustments to the placement of your studs as the anchor sets.
Extreme temperatures generally can be unsuitable for chemical anchors. In situations where they might be exposed to extreme heat, mechanical anchors should be chosen above chemical as even once they’re cured the adhesives used in chemical anchors do have a melting or softening point.
If you want to discuss your anchor-system options or are unsure about one product over another, you can also get in touch with a local White Cap expert. Fill in a quick online form, and you’ll receive a call back within two hours, and an expert in chemical anchoring systems will talk you through what you need for your job as well as how best to use them locally considering weather conditions.
For mechanical anchors, on the other hand, you have to drill a millimeter-perfect hole that’s just a little larger than your mechanical peg. The exact size of the hole needed for a mechanical anchor depends on the type of mechanical anchor you’re using.
The Limitations of Chemical Anchors
Some contractors, particularly those who have been working in the industry for some time and remember a time of less-effective adhesive anchors, think of chemical anchors as complicated to install.While it’s true that adhesive anchor installation has to be carried out carefully, it’s not a difficult process. The most important things to remember are:
- Clean out your borehole properly. Any dust or debris left in the hole will stop the adhesive from adhering to your substrate, leaving you with a weak or completely ineffective anchor.
- Making sure your adhesive is mixed properly (assuming it’s a two-part mixture, which most are). To do this, shake the container your two-part solution came in very well before using an adhesive anchor gun to fill your borehole.
The time it takes for chemical anchors to set can also be an issue on some job sites. If it’s cold or, in some cases, very warm, the setting may take longer than it should or not happen at all. That being said, the extra time can be helpful under normal curing conditions, as you can continue to make small adjustments to the placement of your studs as the anchor sets.
Extreme temperatures generally can be unsuitable for chemical anchors. In situations where they might be exposed to extreme heat, mechanical anchors should be chosen above chemical as even once they’re cured the adhesives used in chemical anchors do have a melting or softening point.
Why White Cap
At White Cap, we have what you need to install a variety of chemical or mechanical anchors. We carry epoxies, adhesive anchor dispensing guns, mechanical fixings, and more. Whether you shop at one of our 360+ brick-and-mortar stores or online, next-day delivery means you’ll have your building supplies in time to start your job.If you want to discuss your anchor-system options or are unsure about one product over another, you can also get in touch with a local White Cap expert. Fill in a quick online form, and you’ll receive a call back within two hours, and an expert in chemical anchoring systems will talk you through what you need for your job as well as how best to use them locally considering weather conditions.
Check out these articles to learn more about Adhesive Anchoring
Factors to Consider When Buying a Caulk Gun
Selecting the Right Caulking Gun Type for Your Project
Maintaining Your Caulking Gun
What are Adhesive Anchors?
Benefits of Chemical Anchors
The Different Types of Adhesive Anchors
Mechanical vs. Chemical Anchors
Determining a Tension Test Load
Infrastructure Applications for Adhesive Anchors
