Figure 2 – Example of a typical polymer liner failure
O B S E R V E D FA I L U R E M E C H A N I S M S
Although many wastewater systems may visually look good for many years after installation, if hydrogen sulphide is present the acidification process has already
begun. A scratch test on the surface gives a better indication as to the depth of the acid penetration and concrete mass loss.
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Figure 3 - Without protection some concrete
assets degrade quickly
Photos in Figure 3 show concrete surfaces, which have
been blasted with water or scratched to expose the
extent of the concrete mass loss.
Figure 4 - Epoxy manholes showing
initial signs of peeling near top lip (left)
and blistering that traps acid behind
(right)
The photos in Figure 4 show epoxy polymer
coating in the initial stages of failure where the
edges peel away from the edges of the surface,
and later in the failure stage where acid has
been trapped behind the coating against the
surface, concentrating the acid attack on the
concrete. All physical barrier polymer coatings
have a similar failure mechanism of peeling
and bubbling as seen with the polyurethane in
Figure 5, which can be very costly to remove at
end of life.
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