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- How to Polish Concrete Countertops
- Sealers for Concrete Countertops
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- Related Reading
- Countertop Product Reviews
- Concrete Countertop Basics: Pricing, colors, edge details, and more
Casting Equipment for Concrete Countertops
Just like you wouldn’t play baseball with a hockey stick, having the right equipment is crucial to casting high-quality concrete countertops. If you are doing a one-time small-scale project, you may be able to forgo some of these, but for the professional who is casting multiple counters of considerable size they are a must.
Although you can mix the small batches of concrete required for countertops in buckets or a wheelbarrow, a portable mortar mixer is more convenient and will blend ingredients more thoroughly.
Buying tip: "Be aware that the typical mortar mixer doesn't hold the same volume of concrete as the rated barrel capacity. For example, a 9-cubic-foot mixer may only be able to hold about 6 cubic feet of concrete. Also, the stiffer the mix the less material the mixer can effectively blend," notes Girard. Consider buying (or renting) a capacity larger than you think you'll need.
A strong, level casting table is essential to properly support the mold and the heavy wet concrete until it cures. Some fabricators save money by building their own casting tables. But if you plan to buy a table, make sure its rigid enough not to sag under the weight of the concrete and large enough to accommodate the average countertop slab. For a standard 25-inch-wide countertop, a 5x10-foot or 5x12-foot casting table works well, says Girard.
Knockouts for Sinks and Faucets
On most countertop projects, you'll need to form knockouts in the countertops for installation of sinks and faucet stems. Since these holes are literally cast in concrete, they must be precise and properly positioned.
Although you can fabricate your own knockout forms for faucets from such materials as PVC pipe, rubber, or foam, you can save time by purchasing ready-made polyurethane or rubber knockouts in a depth to match the countertop thickness. You can also find precision-cut polyurethane templates for sink knockouts. They come in various shapes and sizes to match the dimensions of popular sink brands, such as Elkay, Kohler, and American Standard. Girard notes, however, that premade sink-hole templates are normally not available for high-end or custom sinks. In that case, youll need to make your own.
Buying tips: If you're going to be casting a concrete countertop, why not cast a concrete sink as well for a more unified appearance? Rhodes has designed four fiberglass sink molds for precasting integral vanity, kitchen, and utility sinks. He says that each mold can be reused many times and comes with a rubber knockout for the drain hole.
After pouring the fresh concrete into the countertop mold, you may need to use a vibrator to help consolidate and level the concrete and remove air bubbles that could leave unattractive holes or pits in the surface. Not all countertop mixes require vibration. It all depends on the stiffness of the mix you're using and the effects you want to achieve.
Buying tips: "Makita makes a 12-volt cordless insertion-type vibrator that works well for small projects," says Rhodes. However, since this tool must be plunged into the wet concrete, it tends to disturb reinforcing materials and decorative insets. You can avoid this problem by using table-mounted external vibrators, choosing a size and power level appropriate for the size and weight of your casting table. Even the vibration from a simple jitterbug sander may be adequate, says Rhodes.
Another option to consider when choosing a compaction tool is a table vibrator. This type of vibrator attaches to the casting table with screws and vibrates the entire concrete countertop. One of the key benefits of using a table vibrator is that you avoid disturbing any inlays that are set in your countertops as well as the edge forms. With a insertion-type vibrator (or pencil vibrator) you run the risk knocking your decorative peices out of place. CHENG Concrete offers vibrators in their online stores as well as speed controllers.
Cast in place job with curing blankets taped in place. Concrete Countertop Institute in Raleigh, NC.
If you plan to cast the countertop in place rather than precast the countertop in a shop, proper curing is essential because it's more difficult to control environmental conditions. Curing covers or blankets will help to keep the concrete moist so it cures slowly and evenly.
Buying tip: Look for a material that won't stain the concrete and is reusable to save costs. Girard recommends HydraCure M5 blankets from PNA Construction Technologies. The reusable nonwoven fabric is inorganic so it won't mildew or stick to the concrete surface, and it can be used in indoor environments.