Concrete Carbonation
One of the most common forms of degradation
of structures we see in everyday life is concrete carbonation,
where carbon dioxide from the atmosphere reacts with the
alkalies in the hardened concrete, thereby reducing the
alkalinity of the concrete. This in turn allows the breakdown
of the passivation layer on the steel reinforcement and
corrosion begins. As the corrosion by-products have a larger
volume than the original steel this exerts stresses on the
concrete leading to the spalling and brown rust stains that
are all too common on many structure.
It is a well known fact that all RC structures
start to suffer from concrete carbonation as soon as it
is built yet rarely at this stage does the engineer or client
consider the use of anti-carbonation coatings. Flexcrete
offer a range of cementitious anti-carbonation coatings
that have been proven to prevent the ingress of carbon dioxide
given the equivalent of a minimum additional 80mm of cover
to prevent carbonation in concrete. These anti-carbonation
coatings will also prevent the ingress of chloride ions
and water and by chemically bonding to the substrate will
last the design life of the structure.
Cementitious Coating 851 was applied as
an anti-carbonation coating back in 1990 to the Egginton
Bridge which carries the A38 over the River Dove in Derbyshire.
Here it was found that the carbonation of the concrete had reached
the steel reinforcement leading to corrosion of the reinforcement
and spalling of the concrete. In 2003 a survey was carried
out by Mott MacDonald when tests showed that the depth of
carbonation has reduced proving not only the effectiveness
of the 851 as an anti-carbonation coating but also as means
of re-alkalising the concrete.
For more
details on Flexcrete's Cementitious Coating 851 see:
Cementitious Coating 851 Technical Data Sheet
Cementitious Coating 851 Safety Data Sheet
Cementitious Coating 851 Application
Guide
Other products
in Flexcrete's anti-carbonation coatings range include:
BONDING
PRIMER BBA
Water based epoxy primer for membrane coating systems.
MONOLASTEX SMOOTH BBA
High build, decorative anti-carbonation coating, which
allows damp substrates to breathe.
DECADEX
Proven anti-carbonation coating with a long track record.
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