Formwork for Concrete Structures by R.L.Peurifoy and G.D- By EasyEngineering.net

396 Chapter Fourteen
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be achieved with a satisfactory degree of perfection. It may be desirable
to provide 2- by 2-ft samples to the worker before starting construction
to define the quality of workmanship that is required of the final product.
Concrete Coloring
Concrete that is mixed with normal cement has the traditional gray
color. For architectural concrete, a wide variety of colors may be
achieved by adding admixtures to the concrete mix or by adding a
color hardener to the surface of the concrete after it is placed.
Colored, water-reducing admixtures are added to the concrete
mix to produce a permanent nonfading uniform color. Admixtures
are available in a natural range of earth-tone colors, from rich grays
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to warm reds and colored buffs. Custom-matched colors may also be
obtained for individual designs.
A multicolored textured stone-like appearance for floors may be
achieved by treating freshly placed concrete. Specially graded stones,
selected for attractiveness and brilliance, are intermingled in a granulated
colored cementitious material. When incorporated into the surface
of freshly placed concrete and exposed by sandblasting, the result is a
wear-resistant surface of the desired color. The appearance of granites or
marbles may be achieved in a variety of colors, from pinks with undertones
of black and green to earthen hues with creamy foregrounds.
Floor hardeners are dry-shake hardeners for freshly placed concrete
flatwork. These hardeners are often used to form patterned or
unique shapes for commercial floors, around pools, and for imprinted
concrete paving. Such hardeners also provide the added benefit of
reduced scaling from freeze/thaw cycles and salts.
Stained Concrete
Stained concrete provides an unlimited variety of coloring for concrete
floor slabs. The desirability of acid stains is that the resulted are varied
and often unpredictable because the chemistry of concrete and condition
surrounding its placement has a large impact on the outcome.
Patterns or textures can be applied before the cement sets to further
enhance the final appearance of the concrete.
Acid stains are only one way to color hardened concrete, but it is
the most permanent coloring method because it has a high resistance
to abrasive wear and resistance to ultraviolet light damage. Stains
consist primarily of metallic salt compounds, water, and muriatic acid,
which react with concrete. Types II and V cements are best suitable
for stain applications.
The surface area of the concrete is cleaned of grease or any other
discoloration on the concrete. The stain may be applied by a brush,
mop, roller, or sprayer to cover the concrete work area. Different
results will be obtained; depending on the method the stain is applied.
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