PROJECT SPOTLIGHT
R-625 rig. The piles were spaced three
pile diameters apart centre-to-centre
to avoid group effects and an overall
reduction of bearing capacity. The piles
consisted of 32 MPa type S-2 concrete
and were reinforced with 15M rebar
cages eight to 16 metres in length.
During construction of the CFA
piles for the administrative offices,
piling operations proceeded smoothly
despite frigid winter weather with temperatures
remaining between –10 and
–15 degrees Celsius. Special measures
were taken to maintain the workability
and flow of the concrete at these freezing
temperatures, including choosing
a cold weather concrete mix. Keller
Canada used a CFA concrete mix that
included sulphate resistant cement,
Super Plast and DELVO. Super Plast
plasticizer helps increase the workability
of the concrete without requiring
Winter piling operations proceeded
smoothly despite frigid weather, thanks
to the reliability of the Soilmec drill rigs
extra water, keeping the water/cement
ratio lower to reduce susceptibility to
freezing. DELVO retards the setting
time by controlling the hydration of
the cement. In order to keep the concrete
flowing, Keller Canada’s concrete
supplier also heated the water and
warmed the aggregate with natural gas
heaters.
However, there were three days of
delay when the weather dropped below
–15 degrees Celsius, causing Keller
Canada to suspend piling to prevent
soil from freezing on the flights and
concrete from freezing in the pump
lines.
Special measures were also required
to prevent the uppermost part of the
CFA piles from freezing as the concrete
cured. All of the piles were covered
with exterior, below-grade Batt insulation
after setting the rebar cages; this
insulation was later removed when the
pile caps were installed. If the overnight
temperatures had dropped any
lower, tarps and heaters would have
been required to protect against freezing
as the concrete cured. Luckily the
Batt insulation was deemed sufficient.
Rising above the mud
Once the piles for the administrative
offices were complete, Keller Canada
moved on to install piles for the building’s
bus storage and maintenance
areas. As the weather warmed up into
spring, fast thaws quickly caused the
job site to become entrenched in mud.
Both Keller Canada and an earthwork
contractor had front-end loaders and
skidsteers clearing mud during the
entire shift in order to keep access
roads and work areas clear for the concrete
trucks.
CONTINUED ON PAGE 48
PHOTOGRAPHS COURTESY OF KELLER CANADA.
46 Q3 2015 www.pilingcanada.ca
/www.pilingcanada.ca
