| Concrete Countertops
Decorative Home
> Concrete Countertops
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| Photo courtesy of Jon
Nasvik, Cliffhangers, Inc., Hailey, Idaho
|
Since concrete is such a versatile material, more
and more people are realizing its value in making countertops. Shapes
of countertops are only limited by imagination and the ability to
build the forms. With the use of color pigments in combination with
white cement and various aggregates, the spectrum of colors available
in concrete countertops is virtually limitless.
It’s been more than a decade since concrete
countertops found their way into shops, restaurants, and homes.
Once the realm of either the do-it-yourselfer or the wealthy, they
seem to have gained acceptance in just about every level of residential
application, from moderately priced homes to high-end places.
Nowadays, lots of people have a good feel for what can be accomplished
with concrete countertops. Whether an interior is traditional, contemporary,
or somewhere between, concrete is a versatile medium to express
the aesthetic of designer and owner.
Materials Used in Concrete Countertops
Aggregate
What accounts for the greatest proportions of concrete?
Coarse and fine aggregate. Depending on the look desired, these
materials should be chosen carefully. Coarse aggregate may be exposed
by grinding or polishing, similar to terrazzo. When that is done,
it’s important to get the right size, shape, and color of
aggregate particle. These will all affect the countertop’s
appearance.
From a color perspective, fine aggregate has perhaps a greater
effect, at least on the mortar portion of the concrete mixture.
Smaller particles have a tinting effect on concrete, so the sand
can impart an overall hue to the finished surface.
Binders
Portland cement binders are the backbone of concrete. These
materials glue all the other ingredients into a solid mass. Normal
portland cements have a grayish color, although that varies somewhat
from one source to another, and perhaps even from one batch to another.
For darker colors and plain (untinted) concrete, gray portland cements
are the easiest choice.
For white or lighter colored surfaces, white portland cement is
available. It provides a base that is more easily colored with pigments,
stains, tints, or dyes. It is a type of portland cement and has
the same behavior as its gray counterpart. Here again, sand can
play an important role: when mixed with white cement, sand particles
impart an overall color to the concrete. If pure white colors are
desired, white sand should be used. For other colors, sand should
be compatible with the intended color.
Pigments
These materials come in various forms. For integral coloring,
many are based on synthetic mineral oxides for their durability
and consistent quality. The liquid versions are among the easiest
to use because they disperse readily when mixed into the fresh concrete.
Powder versions have a long history of use, however, and give excellent
results.
Post-applied color is achievable with stains, tints, or dyes. The
basic types of materials are chemically reactive stains and water
or solvent-based dyes and tints. Chemical stains are water-based
acidic solutions. They contain metallic salts that react with calcium
hydroxide in the paste to produce insoluble colored compounds of
blue-green, black, brown, or gold. The stain reacts with the concrete
with a degree of variation, and can result in a non-uniform effect.
To some, that adds to the natural appearance of stains. They can
be used on old or new concrete. Stain also reacts with calcium-based
aggregates such as limestone. Stains should be avoided with lean
concrete mixtures (low cement contents). Prior to staining, concrete
should age at least 14 days; blue, green, and gold colors require
30 to 60 days of curing.
Dyes and tints do not react chemically with concrete. They often
produce colors that are not available in chemically reactive stains,
namely the reds and yellows. They help intensify colors when used
in successive applications or can soften or even out the appearance
of slabs that have been chemically stained. They are water or solvent
based materials and must be applied to concrete that accepts penetration
of materials. The slab should be treated with a degreaser and a
mineral acid solution to reach a surface pH of about 7 or 8 before
dyes and tints are applied. A sealer helps protect the color.
Some manufacturers formulate waxes to work with many of the colored
concrete finishes. They can heighten the slab’s color but
would have to be deemed safe for food. They improve concrete appearance
and help a colored slab retain that appearance, but require periodic
reapplication.
Sealers
In the past, recommendations were to do periodic maintenance
on concrete countertops, but the newer sealers have lessened the
need for this activity. One of the most important considerations
regarding sealers is the finish. Much like everyday paints, sealers
come in glossy, satin, matte, or flat finishes. This aspect of surface
treatment has a big impact on the countertop’s appearance.
The decision should be made with regard to planned lighting for
the space. An article by the Concrete Countertop Institute gives
a detailed description of the types available and a comparison of
their performance characteristics. Click
here for a PDF of the article.
Inlays and Imprints
Countertop designers have experimented with various techniques
to add interest to surfaces. Inlaid materials include shells, fossils,
metal objects and scraps, natural stone, tiles, and other varied
pieces. The long-term durability of the inlay should be considered
when choosing it, although a sealer will normally provide some additional
protection.
Imprints sometimes work in countertops, but shouldn’t be
so deep that they pose a collection area for solids or liquids.
Finishes
The most common finish on concrete countertops is a hard
steel troweled surface. Not only does this densify the skin, it
smoothes out the surface so that it is safe for anything that might
be placed on it.
Sinks
Sinks in homes are kitchen necessities but ones that can
add interest to countertops. The sink can be concrete, either integrally
cast with the countertop or a separate casting, or it can be metal,
porcelain, or composite.
More
on concrete countertops
Frequently Asked Questons
Helpful Publications
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Concrete
Countertops: Design, Forms, and Finishes for the New Kitchen
and Bath
This handsome, lavishly illustrated book is the first on the
subject of concrete countertops, which have enjoyed rising popularity
in recent years. Written by California designer Fu-Tung Cheng,
it provides detailed instructions to homeowners and do-it-yourselfers
for designing, mixing, pouring, forming, coloring, troweling,
in-laying, and finishing decorative concrete countertops. The
book showcases concrete's limitless aesthetic versatility-its
ability to mimic marble, glass, granite, and other materials-along
with its proven advantages of strength and durability. Published
by Taunton Press, publishers of Fine Homebuilding magazine.
LT266—$29.95 |
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Concrete
at Home
Master designer Fu-Tung Cheng leads you on a tour of the most
beautiful concrete design possibilities in Concrete at Home.
Using rich photographic illustrations and clear and comprehensive
text, the book provides fabrication techniques used by the author
as he creates a series of beautiful architectural elements that
includes floors, walls, columns, fireplaces and countertops.
LT288—$29.95
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