It may have been Friday the 13th, but one of Victoria’s largest concrete pours went off without a hitch in February. Starting at 6 a.m., 110 loads of concrete were delivered by Ocean Concrete, Vancouver Island, for the bascule pier of the capital city’s new Johnson Street Bridge.
Over 13 hours, 1,070 cubic metres of concrete were poured without a single load being rejected.
The job wrapped up around 11 p.m. on Feb. 13, when the 40 or so people working on the ground completed the work.
"We plan for the worst, but this went off really good," said Tyler Vander Linden, a project manager with PCL Constructors Westcoast Inc., the general contractor for the $93 million project to replace the 1920s-built bridge that spans Victoria’s downtown Inner Harbour.
Initial plans called for a 24-hour window to complete the pour, but the City of Victoria, owner of the bridge, co-ordinated with PCL and Ocean so that the safest, most efficient delivery route, that would least impact the public, was used.
Flag people were hired and one lane on Johnson Street was dedicated to Ocean’s concrete trucks.
The plan was to have one truck deliver concrete every 10 minutes.
Fourteen trucks were used for the pour to ensure consistent delivery cycling and to eliminate any chances of gapping.
"If a truck was stuck in traffic, it would have a ripple effect," said Vander Linden, a civil engineer who came from PCL’s Seattle office to work on the bridge project in December 2012.
He recently replaced project manager Dan Leachman.
It took each truck about 10 to 15 minutes to reach the site from Ocean’s plant, which is not far from downtown, said Dave Buchanan, Ocean’s manager of operations for Vancouver Island.
To develop a specific concrete mix for the bascule pier, one of the most sensitive components of the bridge project, Ocean and PCL worked together, Buchanan said.
The mix was a high-performance, low heat, high fly ash, high slump and air mix.
Design strength was 35 MPA (mega Pascal’s which are units of pressure) at 56 days, Buchanan said.
However, Vander Linden said the concrete has proven far stronger than 35 MPA.
The concrete was poured into a box-like area, 20 metres by 25 metres and over two metres deep.
The boxy component will serve two purposes, Vander Linden said.
It will be a walking surface so that maintenance staff can access bridge machinery, such as motors and gears.
The pier component is also the foundation for the bascule portion of the bridge, making the concrete structure rather unique.
Because the actual pier sits on top of ocean water, a special cooling system had to be developed, Vander Linden said.
The concrete had to be a mix that did not set rapidly.
"We wanted it to react slowly," he said.
To address the challenge, cooling tubes made of PVC-type material, which had water running through them, were coiled throughout the concrete to control the rate of heat loss.
Two weeks after the pour, the tubes, which stay embedded in the concrete, were filled with grout.
To ensure the pour was wholly successful, Vander Linden said that ongoing visual inspections will continue until the bridge is finished, sometime in 2017.
Several hundred concrete samples were taken from the loads and they are continually being examined.
The concrete pour had been postponed twice due to weather conditions, said Dwayne Kalynchuk, engineering and public works director with the City of Victoria.
The occasional light drizzle on Feb. 13 did not impact work, he added.
While there were reports that the Friday the 13th pour was one of the biggest ever in Victoria, that honour goes to the October 1989 pour at Victoria’s Mayfair Mall for a raft slab.
The joint effort between Ocean and Butler Brothers Supplies saw a continuous pour of 2,100 cubic metres, Buchanan said.
While massive, the Johnson Street Bridge pour was not even Ocean’s largest volume day.
That happened in September 1999 when 1,170 cubic metres were delivered to multiple Victoria-area sites.
For the Johnson Street Bridge pour, Ocean was unable to take on other work that day because the plant, the only wet-batch facility on Vancouver Island, was at full production capacity.
Butler Brothers was on standby in the event of problems, but their concrete services were not required.
Buchanan, who’s been in the concrete business for 40 years, said the pour was complicated due to logistics but "seamless co-operation" between all involved led to an auspicious Friday the 13th pour.
1/2
Courtesy of the City of Victoria
Recent Comments
comments for this post are closed