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

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Forms for Architectural Concrete 397
For example, a sprayer will produce a diffused pattern, whereas an
acid brush yields in a deeper, richer coat. A darker appearance can be
obtained by applying additional coats of stains. A short-napped roller
will ensure additional texture.
Acidic residue is removed after the stain has been allowed to dry
and cure. The procedure for removing acidic residue is generally provided
by the manufacturer of the concrete stain product. After the
staining procedure is completed the concrete surface is sealed using a
brush, roller, or sprayer.
Stamped Concrete
Stamped or patterned concrete involves pouring a slab concrete and then
impressing both patterns and textures onto the concrete before it fully
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sets. Stamped concrete can produce textures that duplicate many different
surfaces, such as cobblestones, brick, pavers, or wood. Also, pigment
can be added to stamped concrete to further enhance the appearance.
The maximum size aggregate for most concrete is 1 to 1½ in. These
size aggregates do not work well for stamped or patterned concrete. The
maximum size of aggregate should not exceed ³⁄8 in. It is desirable to use
round aggregate, sometime called pea gravel, for stamped concrete.
Stamped concrete should be no less than 4 in. thick. The concrete
is placed, screeded, and bull-floated just like ordinary concrete. The
concrete may be troweled before the stamping process. However, it
should not be troweled more than once; otherwise the concrete may
bleed water to the surface.
If it is desired to use coloring in the concrete, the color is added
before the stamping process is started. Coloration can be achieved by
ordering colored concrete or adding the color after the concrete has
arrived at the job. Color added at the jobsite is introduced by shaking
special dried pigments on top of the wet concrete. The pigments are
then troweled into the concrete. The pigments penetrate ¹⁄8 to ¼ in. into
the concrete surface. The concrete can also be stained after it is placed.
Stamps are usually made of polyurethane material to resemble
ordinary building products, such as flagstone, brick, or natural stone.
The stamps are pushed into the concrete and then removed to leave
the pattern. The freshly placed concrete must have sufficient hardness
so the stamp will not sink, but must be soft enough for a clean
stamp. A test of the stamp on a demonstration location should be
performed before applying the stamp on the permanent surface.
Form Liners
Architectural concrete form liners may be used to create virtually unlimited
textured or sculpted effects in concrete surfaces. The surfaces may
simulate wood grains, rough brick, blocks, or an irregular texture, as
illustrated in Figure 14-1. Form liners may be rigid or flexible.
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