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March 2014   

Abuse vs. Impact Resistance

By: Lee G. Jones

Q: There are now several interior gypsum panel products available for high-traffic situations. They are marketed as either abuse or impact resistant panels. How do I know which one is most appropriate one for a specific high-traffic condition?

A: First, you need to understand the difference between abuse-resistant and impact-resistant. Abuse-resistant panels are primarily intended to withstand scuffing and surface abrasion. Think gym bags rubbing up against or along exposed wall surfaces as they are transported through crowded corridors. Impact-resistant panels are primarily intended to withstand direct hits from blunt objects. Think gym bags being launched at teammates between games slamming into the wall surfaces behind their missed targets. Of course, high-traffic areas are likely to be subjected to some of both types of contact, so when choosing the applicable category, you need to determine whether abrasion (abuse) or directly landing (impact) contact is more frequent. Fortunately, most products intended for one of these conditions offer some protection against the other condition as well. And some manufacturers offer products that are designed to handle both.

To keep things interesting and to differentiate themselves from the competition, the gypsum board manufacturers have taken multiple paths to produce abuse and impact resistance to their products. Certain products offer paper facings, similar to the facings found on regular gypsum board products, over hardened gypsum cores. Other products have glass-mesh facings and/or backings intended to improve abuse and impact resistance. And yet another version of these panels has no facing material, in some cases relying on the decorative finish to provide some of the desired durability. Such product diversity makes an apples-to-apples performance comparison a real challenge. Fortunately, the producers realized they needed some means by which to make the comparison, so we now have ASTM C1629, Standard Classification for Abuse-Resistant Nondecorated Interior Gypsum Panel Products and Fiber-Reinforced Cement Panels. ASTM C1629 provides three classification levels in each of four different categories: surface abrasion resistance, indentation resistance, soft body impact resistance and hard body impact resistance.

Surface abrasion resistance is determined using a surface abrasion test. A product’s abrasion resistance classification indicates how well the tested product withstands surface abrasion, which is determined using a weighted scrub brush. A classification of 3 indicates the highest abrasion resistance; a classification of 1 indicates the lowest.

Indentation resistance is determined using an indentation test, which measures the dent inflicted by a 5/8-inch hemispherical projectile at 72 inch-pounds of impact pressure. Materials exhibiting the highest indentation resistance earn classification of 3, and those with the lowest receive a 1. Materials that exhibit more than 0.150 inches of indentation are not considered impact or abuse resistant.

Soft body impact resistance is determined using a soft body impact test. This test is performed with a leather bag filled with steel pellets which is carefully slammed into the sample product. The highest classification is 3, the lowest is 1. Materials that do not resist at least 90 foot pounds of impact are not considered abuse or impact resistant.

Hard body impact resistance is determined using a test. where a weighted ramming arm swings in an arc to deliver increasingly heavier blows to a fresh test sample until failure of the test product occurs. The highest hard body impact classification is 3, the lowest is 1. Materials that do not withstand the minimum 50 foot-pounds of hard body impact are not considered impact resistant.

Armed with this knowledge, you are now prepared to compare the spec data sheets available on the manufacturers’ websites of these products. You will likely notice that the test results of the various products offered are, in most cases, pretty close, but some are better in certain categories and not so strong in others. This is where the anticipated abuse and/or impact a given surface is likely to incur must be considered (along with the product pricing) to hone in on exactly which product will best withstand the particular traffic in a given situation. Note: You will also discover in the data sheets that many of these products require minimum 20 gauge steel framing for their support.

And while it is either expressly stated or otherwise implied on the product sheets, the selection of the finish will play a role in how well a surface will hold up under high-traffic conditions. For instance, a high-gloss epoxy paint or heavy-duty vinyl wallcovering will fare better than builder-grade flat latex paint or grasscloth.

Lee G. Jones is AWCI’s director of technical services. Send your questions to jones@awci.

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