| Rebar, or reinforcing bar, is common steel bar,
an important component of reinforced concrete and reinforced
masonry structures. It is usually formed from carbon steel, and
is given ridges for better frictional adhesion to the concrete.
Armada Steel is a family owned reinforcing steel company, serving the southern
interior of BC since 1983. We are proud to have contributed to the areas
tremendous growth, working prestigious projects, such as
Centuria Urban Village, and
Invue,
and to have forged positive relationships with contractors like
UPA. Armada's
success comes form providing exemplary service competitive pricing and keeping
jobs on schedule.
Use in concrete and masonry
Concrete is a material that is very strong in compression,
but virtually without strength in tension. To compensate for
this imbalance in concrete's behaviour, rebar is cast into it to
carry the tensile loads.
Masonry structures and the mortar holding them together have
similar properties to concrete and also have a limited ability
to carry tensile loads. Some standard masonry units like blocks
and bricks are made with strategically placed voids to
accommodate rebar, which is then secured in place with grout.
This combination is known as reinforced masonry.
While any material with sufficient tensile strength could
conceivably be used to reinforce concrete, steel and concrete
have similar coefficients of thermal expansion: a concrete
structural member reinforced with steel will experience minimal
stress as a result of differential expansions of the two
interconnected materials caused by temperature changes.
Physical characteristics
Steel has an expansion coefficient nearly equal to that of
modern concrete. If this weren't so, it would be useless for
reinforcing concrete.[1] Although rebar has ridges that bind it
mechanically to the concrete with friction, it can still be
pulled out of the concrete under high stresses, an occurrence
that often precedes a larger-scale collapse of the structure. To
prevent such a failure, rebar is either deeply embedded into
adjacent structural members, or bent and hooked at the ends to
lock it around the concrete and other rebar. This first approach
increases the friction locking the bar into place while the
second makes use of the high compressive strength of concrete.
Common rebar is made of unfinished steel, making it
susceptible to rusting. As rust takes up greater volume than the
iron or steel from which it was formed, it causes severe
internal pressure on the surrounding concrete, leading to
cracking, spalling, and ultimately, structural failure. This is
a particular problem where the concrete is exposed to salt
water, as in bridges built in areas where salt is applied to
roadways in winter, or in marine applications. Epoxy-coated
rebar or stainless steel rebar may be employed in these
situations at greater initial expense, but significantly lower
expense over the service life of the project. Fibre-reinforced
polymer rebar is now also being used in high-corrosion
environments.
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| A tied rebar beam cage. |
Rebars in detail (top) atop angle iron (bottom). |
Rebar placement for foundation and walls of a
sewage pump station. |
Two coils of common rebar. |
Welding
Most grades of steel used in rebar are suitable for welding,
which can be used to bind several pieces of rebar together.
However, welding can reduce the fatigue life of the rebar, and
as a result rebar cages are normally tied together with wire.
Safety
To prevent workers and / or pedestrians from accidentally
impaling themselves, the protruding ends of steel rebar are
often bent over or covered with special steel-reinforced plastic
"plate" caps. "Mushroom" caps may provide protection from
scratches and other minor injuries, but provide little to no
protection from impalement.
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