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New technologies could save time on costly concrete repairs

0 957 Technology

by Dan O'Reilly

Building owners and developers have options other than costly, lengthy and disruptive concrete and reinforcing steel repair projects, members of the Building and Concrete Restoration Association of Ontario told attendees at a Construct Canada seminar held late last year.
New technologies could save time on costly concrete repairs

Rather than rip out old concrete and steel and installing new material, technology may be the solution in some cases.

Using a number of case studies, two keynote speakers showed how new and innovative technologies —and some that have been available for a while but are now becoming more popular — are changing their industry.

An example is Carbon Fibre Reinforced Plastic (CFRP) which is used for strengthening concrete, timber and masonry structures, said Greg Dolenc, area manager with Sika Canada Inc.

Over the past few years, "the price of CFRP has decreased about 40 per cent, while steel prices have gone up by six to seven times," he stated.

As a result, owners are now asking for the product, said Dolenc.

A thorough knowledge of the building is mandatory for a successful application, said Dolenc, explaining the post-applied carbon fibre plastic has to mimic the reinforcing steel.

"If there is steel in two directions, then the strips have to be applied in both of those directions," he said.

At the 3080 Yonge St. mixed-use building in Toronto, which is currently being transformed, CFRP strips were used to reinforce the second and third floors to meet new loading conditions. Sections of the floors were reconfigured to allow for stairways and elevators as part of a recladding and revitalization by First Capital, he said. Project partners include Kasian Architecture, EXP Engineering and general contractor Ledcor.

Although CFRP can save time and money on retrofits and renovations, it also has practical applications in new construction, said Dolenc.

"How much does vodka weigh?" he asked rhetorically.

That was a light-hearted reference to another project where CFRP provided an inexpensive answer. A seven-storey, 85-unit condominium building on Dundas Street in Toronto required structural upgrading after the developer successfully negotiated with the LCBO to open a liquor store on the ground floor.

In yet another example of an inexpensive technological solution, Dolenc cited the increased use of embedded galvanic anodes. Connected to the steel reinforcing rods, the hockey puck sized anodes prevent corrosion mitigation to the steel.

"When removing the entire slab is not an option, the owner will consider that an embedded galvanic anode with a post applied MCI (migration corrosion inhibitor) is the engineering best belt and suspenders approach," he said.

In another presentation the audience was given an up-close view of the intricate work necessary to create a new stairwell opening at an office building on Toronto's Bloor Street.

A tenant leasing the 28th and 29th floors wanted the stairwell to facilitate movement between the two floors, explained Daniel Rosa, a structural engineer with Vector Corrosion Technologies Ltd.

That meant the steel reinforcing cables in the designated opening would have to be cut. As the cables were in bundles, rather than individual strands, they had to be cut all at once, he said.

"Special attention is required when cutting live cables," said Rosa, adding that a "take away point" from the project that can be applied to other projects is the need to conduct a thorough pre-construction investigation to discover where all the cables are located.

Some of the elements of the Bloor Street project included the need to shore the open space and conduct a fair amount of work over the Christmas holiday period in order to minimize disruption to the tenant's day-to-day operations, said Rosa.

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