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Adhesives

While carpenters consider adhesives to be a major part of their job kit, masons are not as likely to carry a tube in their toolbox. Granted, there are limited uses for adhesives on masonry job but when those situations arise, it's a good idea to know what to use and how to use it safely.

Where do adhesives come into play? Here is one use, according to Robert G. Finkenaur, director of business development for Polymeric Systems, Phoenixville, Penn.: "From our experience, a mason will use an adhesive in mortarless retaining walls, for example, as a capstone adhesive, attaching the top stone to the wall." Other uses include bonding stone veneer to base materials, as a structural adhesive to connect stone and similar products into a solid piece, and to attach anchors and small pieces such as decorative letters, numbers and signs on walls and entryways.

Bonstone Materials of Mukwonago, Wisc., is another adhesive manufacturer investing heavily into the masonry market. Their Boncrete 414NS is a popular choice for general purpose concrete repairs, and features a convenient 1:1 mix ratio, non-sag gel viscosity, rapid setting time, and a gray color that blends with concrete. It can be used to bond concrete, anchor re-bars and bolts, and repair spalls.

Polymeric's Finkenaur notes that, "In choosing an adhesive, flexibility is important so the bond can withstand freeze-thaw cycles. Materials containing very high solvent levels tend to cure very hard and thus are not flexible enough and are defeated by freeze-thaw cycles."

On the other extreme, he adds, "Typically warm weather will speed up the cure just as cold weather will retard the cure of most adhesives. In hot weather some polyurethane adhesives can bubble. Very cold weather can also prevent some adhesives — like the epoxies — from curing altogether. Frost on the surface can also act as a barrier to proper wetting of the surface."

 The tech sheet for Bonstone Anchor, for example, gives some of the temperature concerns for a two-component epoxy. "All material should be at or above 60 degrees F. Combine the two ingredients at one part of A-100 to one part B-412X. Mix thoroughly — ingredients must be blended homogeneously for proper cure. Best to mix using double mix method. The adhesive, substrate and environment's temperature will affect the working properties of the material. Approximately every 10 degrees F results in doubling the speed of cure. Therefore, at 85 degrees F set time is cut in half, at 65 degrees F the set time is doubled. Do not use on substrate at a temperature below 55 degrees F."

Bonstone Anchor is used for setting anchor bolts, laminating stone to other construction materials, and for stone-to-stone bonding. As with most epoxies, care must be taken in its use. Again, the tech sheet says, "Use gloves, wear eye protection and avoid skin contact. When grinding cured joints, wear a dust mask. Substrate to be bonded must be completely dry and dust free. Mix only the amount of epoxy that can be used in 10 minutes. Avoid stressing joint before complete cure of epoxy. Mask areas that must be kept free of epoxy. Clean uncured epoxy from tools with toluol (toluene) or xylol (xy-lene) — use caution, these solvents are flammable. Ensure local ventilation. Remove cured epoxy mechanically."

Polymeric Systems makes a product called InstaCrete that is very safe for mason use. It contains no solvents or VOCs (volatile organic compounds). "Even so, we recommend the use of gloves if a person tends to have very sensitive skin or the InstaCrete is being used for an extended period of time rather than for incidental repairs," Finkenaur cautions. "For other types of adhesives, such as highly solvent based materials, they can be flammable so the fumes can be dangerous especially in closed areas."

As Finkenaur notes, "I believe 'greener' products are a trend, especially as 'sick building syndrome' becomes a bigger issue. The products that have improved UV resistance and better bonding to porous surfaces are also future advances." Until safer adhesives are available, caution is, as always, the byword in using them and any other chemical on the job site.







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