A heritage jewel and favourite of tourists to
Ottawa, Canada’s Library of Parliament reopened last June following a
four-year restoration, expansion and up-grade that cost more than
$136 million. Among the
project aims were to make this iconic Canadian building, the only
part of Canada’s original
Houses of Parliament to survive the fire of 1916, structurally
sound and safe for staff and
the thousands of visitors each year, while maintaining its charm and
period features. In this major project the Victorian Gothic building, a
copper-roofed octagon
behind the Houses of
Parliament overlooking the Ottawa River, was enlarged by digging below
the structure to create a climate-controlled space to house books and
documents.
Underground expansion also
created problems: the bedrock beneath the original structure needed to
be broken-up without the use of explosives. Then, how to stabilize the
walls of the newly created basement space? After removing the rock, the
plan was to use form-and-pour concrete, but a Manitoba company,
Multicrete Systems Inc.
proposed that instead new
sub-grade
walls be shotcrete, a
sprayed-on concrete, would be advantageous compared to castin- place
concrete. The trial test proved successful, and Fuller Construction
approved the value engineering change to use shotcreting by Multicrete.
After drilling bolts into the exposed rock, over a four month period
Multicrete’s sixman crew applied the shotcrete and readied the surface
for the waterproof membrane. Shotcrete was batched in an Ottawa plant
and delivered to the jobsite in a
ready-mix truck. From the
truck, the earth-damp material was conveyed by hose, with water added at
the spray nozzle. The specialized expertise of a skilled nozzleman is
required as the shotcrete exits the nozzle at 480 km/hr (300 mph) and
there is technique involved in applying it
to the optimal 150 mm (6
in.) thickness. “You can have hundreds of feet of hose
from the pump and with the
use of a long nozzle, there is less scaffolding required. You can also
apply shotcrete in tight spaces and even directly overhead, such as in a
tunnel,” Georg Nickel, co-founder and president of Multicrete says.
More convenient to apply than concrete, it will harden to the same
consistency, strength and bond as concrete, without forms and without
ever sagging.
“This makes shotcreting
ideal for all types of civil repair and restoration projects,” Nickel
adds.
“We’ve proven that properly applied, shotcrete outperforms any
concrete.”
Shotcrete can also be
applied over existing stucco or concrete after the host surface has been
sandblasted and pressurewashed, and will form a strong capillary bond
with the host concrete. In its dry form, shotcrete has the consistency
of dry sugar. It can be shipped in pre-measured bags, each weighing from
700 kilograms (1,544 pounds) up to 1.65 tonnes (3,638 pounds). Each
1.65 tonne bag is equal to .7646 cubic metre (1 cubic yard).
The shotcrete mix is
composed of sand, stone and additives to make it more flowable using
less water, since the more water added to concrete, the weaker it
becomes.
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“We’ve proven that properly applied, shotcrete
outperforms any concrete.”
Georg |
Well-suited to civil projects because
of its strength and both time- and cost- saving application, says
Nickel, shotcreting is
a commonly-used
method in much of the United States and elsewhere in Canada, but is
still relatively unknown in Winnipeg, which is why the Thompson-based
company opened its Winnipeg office and warehouse (on De Vos Road just
north of the Perimeter Highway off Pembina) in 2004.
Originally named
Terracrete, the company was founded in Vancouver in 1989 by Nickel, who
is an engineer. Nickel
built the
company’s Thompson plant in 1991 to serve communities in the North and
became sole owner of the Canadian company, renamed Multicrete, in 2002.
In addition to
mixing shotcrete, Multicrete is the only authorized distributor for
Aliva shotcrete/concrete spraying equipment
in Western
Canada. In its Winnipeg and Saskatoon plants, the company manufactures,
“value-added” equipment
required for
shotcreting and grouting, using imported components. This includes
robotic spray arms, colloidal grout mixers, and grout pumps, all for
sale or lease.
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Multicrete also sells
pre-cast median barriers, base standards and bumper curbs. The remainder
of the business is for mining companies, primarily in the remote North.
Multicrete Systems is a
joint venture partner in Metcrete, which has a multimillion- dollar
contract to produce shotcrete for BHP’s Ekati mine near Yellowknife, to
be completed this year. In another joint venture, since 2002 Multicrete
has worked with Norway House Cree Nation in operating Keewatin Concrete
Ltd. Keewatin’s projects include several Norway House projects such as
the new high school.
Through the Mines Training
Society, Nickel and Multicrete’s staff have trained 16 aboriginal
workers from Metcrete, in Flin Flon as forklift and front-end loader
operators and shotcrete nozzelmen, “and we hope to do something similar
in Nelson House, where there is a huge employment pool.
We realize people in the
North do need the training. They have the desire to participate in these
big projects and gain long-term employment skills,” says Nickel.
“And we’ve found that with
training, they are really good workers. They make good employees.” Other
recent Multicrete projects include the water treatment plant in Gillam,
shotcreting the inside of three CN rail tunnels near Minaki, Ont. and
restoration of the exterior of Wabowden Public School, where the old
stucco was crumbling. For this application, Multicrete made a custom
shotcrete mix with white cement and white aggregate blended with short
polypropylene fibres to provide tensile strength.
This was sprayed to a 25 mm
thickness over the existing stucco. So why is shotcreting a Northern
success story little known in the south of Manitoba? “It’s just a bit of
an unknown to architects and contractors,” says Nickel, “but we’re
working to change that. About 20 per cent of Multicrete’s work is for
construction projects, including materials and rental equipment, though
this area is the fastest growing. Dry, premixed concrete in bulk bags is
a relatively new product, which is gaining popularity. The
pre-measured, pre-mixed bags “are perfect for the smaller jobs in the
North,” such as an RCMP station or community health centre, says Nickel.
“This is how communities in
the North are able to do concrete work,” since concreting can now be
performed successfully at temperatures as low as –40 degrees C.
Customers often tell us that using these Bulk Bags makes concrete as
easy as making a cake. Just take the product, add water and stir, says
Nickel. “It’s that convenient. And the results? Success, every time.”
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