There are but a few ingredients required for making concrete counter tops. Ready-to-use concrete mix from a bag can be used with a few additives. The prime additives are:
- Water reducer
- Poly-fibers
- Pigment(s)
- Portland cement
- Bonder for adding to cement slurry for filling in pinholes
- Concrete sealer
Sources of Additives and Concrete for Countertops
Shop around to find out what ready-to-use bagged concrete mixes are available locally at building supply stores and then do some research to find out which one has the highest cured strength. The manufacturer can provide this information in terms of pounds per square inch. The finished countertop should have a strength of at least 5000 psi. An extra shovelful of Portland cement will be added per bag to further strengthen the cured counter top.
The water reducer is used to make the mix more plastic without having to add more water. By having less water in the mix, the risk of the mixture shrinking and later cracking is reduced. Water reducers can be hard to find however. It may be possible to get a local concrete mixing company to draw a quart out of one of their 55 gallon drums. Alternatively, Cheng Concrete sells the NeoMix Original Water Reducer in 10 ounce containers.
Poly-fibers are added for the same reason – to reduce the chance of cracking. Some fibers have the problem of floating to the surface of the concrete and leaving a dog hair look on the surface. It is best to mix up the entire batch of concrete with all additives except the poly-fibers and then fill the bottom half inch of the mold and up the walls of the mold with the fiber-free concrete. Then turn the mixer back on and add the fibers slowly a few at a time. Finish filling the mold with the fiber filled concrete. Poly-fibers are available at most concrete suppliers.
Pigments are added to achieve the desired final color. Pigments can be purchased as a powder or a liquid. Concrete pigments can be sourced from concrete suppliers and building supply stores. Most pigments will be labeled as concrete pigments but another good source of pigments are powdered stucco pigments. Pigments can be blended to create custom colors. It will be necessary to make several small sample pours if color surprises will not be appreciated.
The bonder is typically a latex or acrylic additive used to help make the cementious slurry mixture (used for filling pinholes and voids) bond to the concrete slab. Building supply stores will have these products, even Weldbond can be used for this purpose.
Concrete Countertop Tools and Materials
- ¾ inch melamine-covered particle board for mold making
- Silicone for sealing the mold
- PVC pipe or circular pieces of wood for making knockouts for faucets, taps and soap dispensers.
- Packing foam for wrapping knockout molds to make mold release easier
- Clear packing tape for waterproofing knockout molds
- Painted aluminum flashing to create divides if there will be breaks in the slab within a single mold
- Reinforcing lath or 6 inch square steel grid for placing in center of concrete slab to reinforce concrete
- Measuring cups
- Measuring spoons (for pigment)
- Scale for weighing pigments and poly fibers
- Stir sticks for dissolving pigment into water
- Concrete trowels
- Variable speed grinder
- GFCI plug outlet for grinder
- Rubber boots (to avoid the chance of electric shock while operating wet grinder)
- Circular diamond grinding/polishing disks from 50 to 1500 grit
- Velcro backed grinder attachment for polishing disks
- Diamond polishing hand pads
- Sturdy table(s) to hold concrete slabs during curing and finishing
Most of the tools required are easy to find at building supply or kitchen stores. The exceptions to this are the grinder and the diamond polishing pads which are trickier to find.
Relatively expensive variable speed water-fed concrete grinders can be purchased. It may be possible to rent one but they are not commonly available in less populated areas. Another option is to have an electronics technician make a variable speed attachment for a regular angle grinder. Standard angle grinders run in the 10,000 rpm ballpark. Concrete counter top grinding requires speeds between 2000 and 6000 rpm. If using an angle grinder, find one with a double insulated motor and a three-prong grounded plug.
Circular diamond polishing pads which attach with Velcro to the grinder attachment can be ordered online from Buddy Rhodes or found at specialty concrete supply houses. It will be necessary to also get diamond hand polishing pads for manually grinding any hard to reach spaces like the exposed inside edges of undermount sink openings and the front edges of the counters.
Build or strengthen a table to support the concrete slabs. Cured concrete weighs approximately 150 pounds per cubic foot and it's nothing to have two to three cubic feet of concrete in a single length of kitchen counter. If the job requires a few lengths of counters all of the same color, ideally the pour should all be done at the same time and a few tables will be required.
Moving on with the Concrete Countertop Project
This article is the first in a series of articles for making concrete counter tops in molds. The next article details how to make the mold for a counter top and subsequent articles describe making a practice concrete counter slab before moving on to polishing and grinding the final concrete kitchen counter.
Gathering all the ingredients and supplies is no small task and may require a bit of sourcing and researching. Once all the materials are in hand, continue with reading the next article in this series on making the counter top mold.
Related Articles:
- Pouring a Concrete Countertop: How to Mix Concrete and Fill Molds for Cement Countertops
- Finishing Concrete Counters: How to Cure, Grind, and Polish a Concrete Counter Top
References:
- Cheng, Fu-Tung. Concrete Counterops. Taunton Press. 2002.
Susan Noppe - Susan Noppe is a freelance writer who started her writing career seventeen years ago with health care and employment publications before ...
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