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Comparing Concrete Fasteners

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There are numerous ways to determine which concrete anchor to use. One method is to compare the different types and styles of concrete fasteners to meet the needs of the specific application. A concrete fastener of any type only holds as well as the base material in which it has been fastened. In most cases, the base material gives out, not the anchor itself. When properly set, the concrete fastener pulled to the ultimate load capacity of the anchor will pull out the base material adhered to the anchor.

There are a number of ways to compare concrete fasteners. When comparing the same type of concrete anchor from one manufacturer to another in terms of pull out or shear values, it is important that the numbers are in a form that can be compared. Some manufacturers publish ultimate holding values while others publish safe working load values. The safe working load is 25% of the ultimate load value. To compare the two, either multiply the safe working load numbers by 4 or divide the ultimate loads by 4. This will provide numbers that can be compared. The tables that are used for showing the tested holding values are separated into other categories that need to be examined when comparing against a table from a different manufacturer. It is also important to make sure that the diameters of the anchors are the same. Most tables have a number of different hardness of concrete that the anchors are tested in. These hardness are usually 2000psi, 3000psi and 4000psi. These numbers refer to the strength of the concrete measured in pounds per square inch (psi). Making sure that the holding values compared from the same psi concrete are important because of the stronger the concrete- the better the holding values of the anchors. If the two manufacturers' tables do not have the same psi testing, then generally the numbers can be straight line interpolated. The other numbers on these charts that are important for comparisons are the embedment depths at which the anchors are tested. With concrete anchors, deeper embedments result in better holding values. Most charts will have a number of different embedment depths at which the anchors were tested.

Different styles of concrete anchors are manufactured for specific applications and some are more versatile.  Versatility in a concrete anchor relates to the number of different types of base materials that it can be used in. Versatility is achieved at the expense of something being given up or lost. In the case of concrete anchors, holding values are compromised. The more versatile a concrete anchor is, the less the holding values are compared to a less versatile fastener. The wedge anchor, drop-in anchor and concrete strike anchor can only be used in solid concrete and have the highest & most consistent holding values in concrete. Concrete sleeve anchors can be used in concrete, brick or block but their holding values are less in terms of shear and pullout values.

When comparing wedge anchors from different manufacturers, it is essential to remember that they are all basically the same item with different features. Many of these features differentiate a specific brand or allow for benefits that the manufacturer feels is important. Previously, all wedge anchors had a specific thread length for each different length of the anchor. But the manufacturing process changed and wedge anchors are now made using different machines. This different manufacturing process allowed for longer thread lengths without increased costs. These extra threads are sold as a feature. The bullnose on the wedge anchor is another feature that has been added over the years. During installation, the threads can be damaged when pounding the wedge anchor into the concrete. In the past, the nut was put on the wedge anchor to protect the threads and with the pull nose, this is unnecessary. Essentially all wedge anchors are the same, are made from the same basic materials, have threads and a clip that wedges the anchor into the concrete. Each manufacturer's clip is slightly different and each claims that their clip is superior for various reasons. While each clip has its own unique features and benefits, they all work in a similar fashion to provide the same results.

Concrete anchors can have approvals which are compared to determine which anchor should be used. When it comes to approvals for concrete fasteners, it is basically a process that a manufacturer pays for and receives. It is not actually an approval but more like a paid process that gives specific information and credibility to the anchor. The information derived from the process is valuable and can be essential when using a product. Different geographic locations may require specific requirements for the use of fasteners being used in that area.

Today, most concrete fasteners are manufactured overseas in China or Taiwan. Only a few are manufactured in the US. Although the products are not American made, many sellers of concrete fasteners will package their product to make the consumer believe that the product is made in the United States. Over the last 10 to 20 years, each product has slowly been eliminated from the production lines here and sent overseas. The wedge anchors that are still manufactured in the US are the Thunderstud brand wedge anchors. Tapcon® concrete screws are also still made in the US as well. Note that when comparing the price of an American made product to the imported product, the American made anchor will cost more.

Before starting any fastening project, it is important to understand the factors that need to be considered when comparing the different types and styles of concrete anchors. Each unique application will demand concrete anchors with specific features. Choosing the right concrete anchor is an essential part of a successful concrete fastening job.

Purchase Anchors

Sep 23rd 2009 Bob Carlisle

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