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gfrc countertop with integral sink by brandon gore How To: Mix and Mold GFRC

skillbuilder concrete 158x158 How To: Mix and Mold GFRCConcrete, as most folks know, is strong under compression but weak under tension, and is commonly strengthened by casting it around, e.g. a grid of steel reinforcing bar (“re-bar”). Glass Fiber Reinforced Concrete is, well, pretty much exactly what it sounds like: concrete reinforced with glass fibers. As in most composite materials, the fiber elements in GFRC can be carefully oriented, or randomly distributed, in the solid matrix. The nice thing about the latter method is that you can just mix the reinforcing fibers into the bulk concrete and don’t have to pre-position them in the mold. GFRC concrete panels can be much thinner and lighter than metal-reinforced slabs, and the glass fibers are not subject to corrosion.

brandon gore gfrc mixing montage How To: Mix and Mold GFRC

If you’re interested in experimenting with GFRC, however, you may have noticed that practical how-to information is a bit scarce online. The notable exception, IMHO, is this pair of hands-on tutorials from Brandon Gore (who produced the cool concrete coffee table with cast-in saucers we hit last Friday), first published in Concrete Decor magazine in the summer of 2008 and now freely available on their website.

brandon gore gfrc application montage How To: Mix and Mold GFRC

In the first, Brandon details three different concrete mix recipes used in the casting of a GFRC bathroom counter with integral sink. These are the “face coat,” which is sprayed in to line the mold and does not contain fibers, the “vertical backing coat,” which is applied behind the face coat to the panel’s upright surfaces, and the “self-consolidating backing coat,” which fills in the rest. In the second article, Brandon covers the process of actually applying the mixtures to the mold. [Thanks, Brandon!]

Concrete Decor – GFRC Mix Design
Concrete Decor – GFRC Application

Sean Michael Ragan

I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I am a long-time contributor to MAKE magazine and makezine.com. My work has also appeared in ReadyMade, c’t – Magazin für Computertechnik, and The Wall Street Journal.


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