| Fly
Ash |
| Silica
Fume |
| High-Reactivity
Metakaolin |
| None |
|
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Cement:
|
White |
White + Pigment |
Gray |
Gray + Pigment |
|
| Metakaolin can be
used in white portland cement concrete without
compromising its brilliance Mixed into ordinary
gray pordand cement, it gives the concrete a
lighter value that can create new aesthetic opportunities.
It can also be used in integrally colored concrete
to lighten and intensify color, and its whiteness
and uniformity make it easier to match colors. |
|
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Concrete appearance
In addition to brighter and more consistent color, metakaolin
improves concrete appearance in several important ways: • The improved workability of metakaolin-enriched
concrete enables contractors to achieve smoother, denser
finishes without over troweling. This results in less trowel
bum, reduced mottling, and fewer surface blemishes. • Metakaolin makes concrete denser so it is less likely
to absorb stains that could disfigure a surface. • As a highly reactive pozzolan, metakaolm consumes
lime that might otherwise cause efflorescence. And it resists
moisture penetration that can dissolve and transport lime
and other soluble minerals to the surface of concrete. • Alkali silica reaction (ASR) is a chemical reaction
between the alkaline lime in concrete and the silica in some
types of aggregate. If not mitigated, ASR can crack concrete.
Metakaolm is one of the most effective admixtures for preventing
ASR and allows crushed recycled glm to be used in decorative
concrete. • Improved durability: Nothing ruins the appearance
of decorative concrete more dim cracking, corrosion, spallmg,
or other forms of concrete deterioration, By boosting concrete
strength and density, metakaolin provides a safety factor
to help keep your work looking its best Metakaolin-enhanced
concrete.
Metakaoline-enhanced concrete
One concrete contractor who has embraced metakaolin is Alan
Bouknight, president of Azzarone Contracting Corp. in Mineola,
N.Y. He says, "I made samples with metakaotin and put
them out in the yard to watch how they fared. After more
than three years of exposure to the elements, they show none
of the pitting and deterioration we get with typical concrete
in our harsh urban environment."
Since then, Bouknight has used metakaolin in exposed concrete
floors for a fashionable Armani Casa showroom, to create
a sculptural concrete stairway for the Museum of Modem Art,
and for pool decks for a custom beachfront residence. "Metakaolin gives the concrete more 'butte? and enables
me to coax out the inherent beauty of concrete in subtle
ways," he says. "It makes concrete more consistent
so we can create an ultra smooth surface without flow lines
or objectionable blemishes." Used with white portland
cement, metakaolin "can produce beautiful opalescent
finishes. Plus, the bright white metakaolin helps intensify
the color we are after." Tom Ralston, president of Tom Ralston Concrete in Santa
Cruz, Calif , is experimenting with metakaolin for concrete
countertops, Using dosages of up to 10 percent or 15 percent
of the cement weight. "Metakaolin will prove to be a.
very important additive as we continue to improve our countertops," he
says. "It fills in voids and supports the sand particles
to ease finishing. Instead-of taking three or four swipes
with a trowel, you might-need only one or two to get a smooth
hard finish."
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