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REBAR SPACERS & PRECAST CONCRETE ACCESSORIES
WHY CHOOSE PLASTIC SPACERS OVER STEEL SPACERS?
CORROSION is an electrochemical reaction similar to the process that takes place
inside a battery. In reinforced concrete, the rebar and metal bar supports act as
electrodes. Salt laden water forms the electrolyte. The combination of the positive
electrodes and negative electrolytes create a force of energy throughout the concrete
similar to a battery. With time, this process of electrical currents flowing between
positively and negatively charged metal will consume the rebar and metal bar
supports. The result is corrosion.
Corrosion deteriorates concrete and steel leaving structures exposed and unprotected.
After a few winters of de-icing salt or a few years of seaside weathering, corrosion
related problems are sure to occur. This unchecked corrosion costs our country
billons through the repair of structures condemned before their time. Corrosion can
shatter a roadway or destroy a bridge, creating serious safety hazards.
HOW DO REBAR AND METAL BAR SUPPORTS ENCASED IN SEVERAL
INCHES OF CONCRETE DEVELOP CORROSION?
Where reinforced concrete is not exposed to de-icing salts or seawater, the reinforcing
steel will remain essentially uncorroded for the life of the structure. The alkaline
environment in concrete creates a protective, passivating layer on the rebar and
metal supports. But when concrete is in frequent contact with water containing
sodium chloride or calcium chloride, its tiny capillaries are gradually permeated by
salt solution. Soon, chloride ions will penetrate the passivating layer and reach the
rebar and metal supports, triggering corrosion.
A corroding metal bar support will progressively weaken; losing cross section and
causing the surrounding concrete to lose its mechanical grip on the steel. But long
before the steel fails, the concrete is destroyed by disruptive effects of corrosion’s
by product, rust.
When steel rusts, the red oxide occupies up to four times the volume of uncorroded
metal. As it expands, rust can exert pressures up to 4000 psi on the concrete around
it. Forces of this magnitude within the concrete causes cracks and delamination
followed by spalling or other surface damage. A delaminated, spalled surface will
admit even more salt solution, accelerating the corrosion process and compounding
the problem. As spalling exposes the rebar and metal bar supports to the air,
corrosion rates approach that of completely unprotected product.
WHY DO POLYLOK PLASTIC SLAB BOLSTERS, STACKABLE CHAIRS, AND
WHEEL CHAIR SUPPORTS MINIMIZE THE PROBLEM?
As (Figure. A) shows, when a metal chair is used to support the rebar, the area of
electrically charged metal is much greater than when a plastic chair is used
(Figure. B). This vast reduction in electrically charged areas means a vast reduction
in total overall cracking and delamination, thus reducing the admittance of salt
laden water and further rust and corrosion. Polylok plastic slab bolsters, stackable
chairs, and wheel chair supports minimize corrosion and maximize the life span
with unmatched cost effectiveness.
Concrete Concrete
Figure. A Figure. B
PATENTS:
U.S.A.
5,347,787
5,666,768
5,592,785
5,130,016
6,789,776
Canada
2,162,849