Adhesive anchors gain a foothold

Gaining popularity over cast-in-place anchors, adhesive anchors offer flexibility and performance.

by Jason Liebreich

The strength and inherent versatility of adhesives make them one of the fastest growing product categories in anchoring. From residential and commercial construction to the industrial and highway markets, they are used for applications such as seismic hold-downs and mudsills in concrete, rebar dowelling, anchoring steel columns, mounting ledgers, anchoring machinery and many other uses.

Restoration/repair/retrofit contractors have found a valuable tool in adhesive anchors. Building materials, such as red brick, clay tiles or cinder blocks in older buildings are very soft. In situations where anchors are needed in these materials, adhesives bond with the soft material, often exceeding the strength of the base material itself.

Adhesive anchors are also used to correct mistakes on jobsites. Many times, they replace cast-in-place anchors that were missed or put in the wrong place.

Adhesive anchors are gaining in popularity over cast-in-place anchors because they can be precisely installed through a structural element or fixture when it is laid in its correct place.

Adhesives push out other anchors
Adhesives anchors are replacing other anchor types because of their performance and flexibility.  Because the adhesives bond rather than expand, they can be used closer to the edge of the base material than expansion anchors. The same is true for multiple anchors placed close to each other, such as in a steel column’s four-bolt baseplate. 

Adhesives are also resistant to vibration and are often specified where an anchor may vibrate loose. 

For general anchoring jobs, adhesive anchors may be used instead of expansion anchors because they have a greater holding power when compared with expansion anchors of the same, or often larger, size. In some cases, it makes the installation more economical because it costs less to install fewer adhesive anchors to get the same job done. 

In many dowelling and anchoring applications, adhesive anchor cartridge systems are being used instead of the older, more expensive capsule-type adhesives. They cost less and don’t require special tools to “spin in” the anchor. They also have fewer shelf life and handling restrictions. 

New acrylic adhesive formulations open the temperature window where epoxy anchors can’t be used. The new formulations dispense easily and can cure in temperatures as low as 0 F. This relatively new technology has been a huge help to construction crews working in bitter cold weather.

Installation flexibility drives popularity
Adhesives often work in many different applications. Some adhesive anchor products have been tested in core-drilled holes as well as holes drilled with a rotary hammer or rock drill. Many also work well in wet or damp holes and some can even be used in marine or underwater applications.

For larger diameter anchors (1" and above), adhesives are widely favored over expansion anchors such as wedge anchors. An adhesive can work with any rod diameter; you just drill a larger hole and use more adhesive. Plus, because of their more expensive manufacturing process, larger-diameter wedge anchors often are significantly more expensive than smaller diameter anchors.

Adhesives are most widely used in the western United States because of the experience engineers and contractors have had with them on seismic retrofit projects in the late ’80s and ’90s. They were the first anchor type that could meet ICBO seismic load specifications.

Due to engineers’ and contractors’ familiarity with the anchors and their ease of installation, engineers have started specifying them in more applications. Adhesive anchor use continues to grow in other areas of the country as well.

Choose the right adhesive anchor
Adhesive anchor selection depends upon who is making the choice. Some believe that all adhesive anchor products are roughly the same, but this is not the case. 

An engineer will typically look closely at the strength of the adhesive and to the depth and breadth of test data as well as code reports. If an engineer looks at a product with average strength that only shows load values in concrete and has no ICC (formerly ICBO) evaluation report, it’s unlikely that product will be widely specified.  However, if the engineer considers a product that has a strength advantage and also shows load values in multiple base materials and applications that are included in an ICC report, the engineer is more likely to specify it.

Contractors often focus their selection criteria on price, performance characteristics and dispensing speed. Many variables affect cost, but like most things, you get what you pay for. A bargain-basement adhesive anchor product is likely not as high quality, may have a lower strength and will not have as much performance test data.

Performance can also be measured in cure time. If the contractor wants to be able to load the anchor soon after installation, an adhesive with a one- to two-hour cure time can be specified vs. a standard product that may require 24 hours cure time before loading. 

Dispenser selection and care
As the interest in adhesive anchor systems has grown, manufacturers have refined cartridges and dispensing tools to make their use easier and more efficient. There are several cartridge systems available that match dispensing speed and volume to the job.

For jobs with a limited amount of anchors or a wide range of installation locations and times, smaller cartridges (ranging from 5 to 22 oz.) and manual tools are suitable. In contrast, a contractor installing 10,000 dowels on a bridge retrofit project will be better served by larger (56 oz.) cartridges that are dispensed with a pneumatic dispensing tool.

Just as in the adhesive anchor compounds, when it comes to dispensing tools, you get what you pay for. Some tool sources that are typically not in the adhesive anchor business offer tools that are much less expensive than those offered by the manufacturer of the adhesive. These lower-quality dispensing tools can result in breakdowns on the jobsite and can dispense the adhesive at the wrong ratio, which will result in poorly performing anchors.

No matter which dispensing system you use, you will get the best results if you maintain and clean the dispensing tool regularly. During application, workers are bound to get adhesive on the tool which can affect the tool’s performance, so clean them regularly. These tools must also be lubricated as directed to assure proper tool operation. Regularly maintained tools will last much longer and won’t fail in the middle of a job.

Editor’s note: Jason Liebreich is the marketing services manager at Simpson Strong-Tie Anchor Systems.

Published in the September/October 2003 issue of Contractor Tools and Supplies magazine.

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