Carbon fiber reinforces concrete for kitchen countertop

Concrete is becoming a kitchen designer's material of choice, thanks in part to a lightweight corrosion-resistant, nonwoven carbon fiber/epoxy-based reinforcement grid called MeC-GRID, which took top honors in the "Building & Construction" category at this year's JEC Awards in Paris (April 1-3). Developed by TechFab LLC (Anderson, S.C., U.S.A.), a 50/50 joint venture of Hexcel (Dublin, Calif., U.S.A.) and Chomarat Composites (Le Cheylard, France), MeC-GRID can be used in place of steel wire mesh and light rebar. Produced by aligning superimposed warp and weft fibers - Zoltek Corp.'s (St. Louis, Mo., U.S.A., select 228) Panex 033 25K and 50K carbon fiber tow - and impregnating them with a rapid-cure epoxy to create an open grid. The product features 6.35-mm/0.75-inch to 76.2-mm/3.0-inch openings, depending on strength requirements and the application. The lightweight grid is available in rolls that simplify storage and ship via overnight carrier (unlike rebar, which must come in on a flatbed truck).

For a recent 10-ft concrete countertop cast for a custom home kitchen, Mark Concrete (Watsonville, Calif., U.S.A.) selected MeC-GRID CT 550, an 11 oz/yd2 grid with 46.7-mm/1.8-inch by 41-mm/1.6-inch openings, which provides minimum 1,000 lb of strength per strand in both warp and weft (crossover shear strength is 40 lb per mesh junction, with minimum warp/weft tensile strength of 6,550 lb/ft by 7,500 lb/ft). "I use Mec-GRID just below the finished surface, where it will do the most good," says company owner Mark Lesnick. By contrast, several inches of concrete would be required to protect steel mesh from corrosion and prevent rust stains from bleeding through to the finished surface. Mec-GRID's very low profile allows its use in combination with thicker steel wire mesh in his 1.5- to 2.0-inch thick countertops.

The Mec-GRID is cut to size with sheet metal shears and laid into the handmade form. Standard steel mesh and rebar are laid over the MeC-GRID, and the materials are assembled into a reinforcement "mat" with special spacer ties. The "mat" is then removed and what will be the top 6.35 mm/0.75 inch of the countertop (custom-mixed colored concrete) is poured into the form and leveled. (This eliminates "shadowing" - a visual pattern that can remain in the concrete's cured surface if concrete is poured through the mesh.) Then the mat is put in place and the remaining concrete is poured, consolidated with Lesnick's external vibration system and allowed to cure.