Australian Concrete Protects
City and Waterways Against Poisonous
Leachate.
CEMENTAID EVERDURE CALTITE SYSTEM
Landfill
Retaining Wall & Leachate Barrier
Redhill
Creek, Hamilton, Canada.
PROJECT OWNER: City
of Hamilton, Ontario, Canada
In the early 1950's, a large landfill
/ garbage dump adjacent to Redhill Creek in Hamilton
Ontario, had been opened to serve the needs of the
City Hamilton and it's residents In the 60's it
was closed and capped..
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As with many early landfill
sites of this type, little or no sorting
of waste was conducted over the larger
portion of its operation. (e.g.
domestic / industrial wastes, etc) and
in the intervening years rainwater had
percolated throughout.
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After more than 10 years of active
operation, and 40 years since capping, poisonous
leachate from both the industrial and domestic waste
had accumulated within the fill, and threatened
to seriously contaminate the natural groundwater.
The leachate is considered to be
very toxic and unless contained / prevented from
entering the groundwater and draining into the adjacent
creek Lake Ontario, could pose a significant hazard
to the health & safety of the City's residents
as well as to the surrounding environment. The decision
was taken by the City to construct a retaining wall
leachate barrier to provide a long-term solution.
However, the retaining wall / leachate barrier structure
itself would need to be fully waterproof, AND resistant
to the corrosive effects of the leachate.
Conventional membrane-type barriers
as used in the past were not considered suitable,
not only due to the risk of damage, but also because
several of the potential leachate contaminants (e.g.
acids, toluene, etc.) are likely to destroy the
membranes themselves. Normal absorptive concrete
on the other hand, would also be subject to corrosion
attack & degradation by organic acids and other
leachate contaminants being drawn into the concrete
by capillary forces..
Working together with consulting
engineering firm McCormick Rankin, the City of Hamilton
specified the concrete to incorporate "Everdure
CALTITE", a time-proven Hydrophobic Pore-blocking
Ingredient with a more than 45-year track record
of corrosion-free service under some of the world's
most severely corrosive environments. "CALTITE"
reverses the normal capillary "wicking" or absorptive
action in concrete, producing instead concrete with
a uniformly Hydrophobic MatrixT as well as capillary
pore-blocking components, which actively expel water
and any contained salts or acids and prevent their
re-entry. The interior of CALTITE concrete remains
DRY in-service, and so unaffected by acids or salts
in contact with it. The action of acids is confined
to only the extreme outer surface, where only insignificant
wear can occur.
The structure itself is in effect
a caisson wall with reinforced concrete facing.
The "caissons" are all 39"
(1.5m) in diameter, augured into bed rock 15 - 18m
from the surface. There are 2 different mix designs
for the piled wall structure, the first being a
6mpa mix - mostly a high sand mortar type mix. These
piles were augured into place first, and then the
"King Piles", using a 35mpa conventional
mix, were augured between the "fillers".
A steel cage for the "tie backs" was placed
in the king pile casing before filling with concrete.
The face of both piles is cut back by the
action of removing the garbage. FInally a 35mpa
reinforced Caltite concrete wall of 350mm minimum
thickness is to be cast as facing.
The Everdure Caltite ingredient
is added to the concrete during batching at the
rate of 30 Litres/m3, to replace an equal amount
of batch water. The fully waterproofed and corrosion-proofed
concrete arrives at the site ready to pour, place
and forget!
Dufferin Construction is the Contractor,
Dufferin Concrete the Concrete Supplier and Bermingham
Construction the Piling Contractor. With a final
total of approx. 1,200cu.m of Caltite concrete to
place, work commenced in late 2004, with completion
anticipated by August 2005.
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