ARCHIVED - New Cornwall Bridge to be built with stronger concrete developed by the NRC
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Durable concrete will increase the average lifespan of bridge decks by more than 20 years
October 05, 2011 — Ottawa, Ontario
The National Research Council of Canada (NRC) has developed a more durable concrete that will increase the average lifespan of bridge decks by more than 20 years compared to typical high-strength concrete, and by more than 40 years compared to normal-strength concrete.
This high-performance concrete has been specially formulated to minimize shrinkage, which is typical of high-strength concrete, while maintaining its excellent mechanical properties. It also greatly reduces cracking, which diminishes the penetration of aggressive agents into the concrete, such as chlorides from the de-icing salts used on roads. As a result, it takes considerably more time for the chlorides to reach the steel reinforcement, initiate corrosion, and induce further damage to the structure.
“The key difference is in the sand—lightweight porous shale fine aggregate, which replaces about a quarter of the normal sand used to make concrete,” says Dr. Daniel Cusson, a senior researcher at the National Research Council. “This porous sand can hold up to 20 percent of its own weight of water, which serves to uniformly cure the concrete from the inside, thus preventing self-desiccation.”
With a unit cost only 5 percent higher than that of standard high-strength concrete, Dr. Cusson expects concrete bridge decks made with this new concrete will last longer, save taxpayers money from annual bridge maintenance, recurring repairs and associated traffic disruption and replacement.
Currently, this new self-curing high performance concrete is being put to the test at the NRC outdoor slab testing facility, where its mechanical performance and corrosion resistance is being monitored with embedded instrumentation and periodic non-destructive testing.
This new concrete formulation is being considered for the deck construction of the Canal Bridge, which is part of the North Channel Bridge replacement project in Cornwall. The $75 million infrastructure project from Federal Bridge Corporation is currently underway.
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Enquiries: Media relations
National Research Council of Canada
613-991-1431
media@nrc-cnrc.gc.ca
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