Paving the way to concrete results
As roads and bridges in Canadian cities suffer from the effects of harsh weather, heavy traffic, road salt and acid rain, a new cross-border bridge in Cornwall, Ontario stands strong. Built from a new class of concrete, the deck of the Canal Bridge – part of the Seaway International Bridge system— is expected to require significantly less maintenance than most of the other 80,000 bridges across Canada, ensuring safe and efficient travel for the more than 2.3M drivers who use it each year.
Bridge decks made from traditional concrete typically last up to 25 years before they need significant repairs or replacement. This new concrete, developed by the National Research Council (NRC), can last up to 100 years before requiring major repairs under similar conditions. It also displays very low shrinkage and permeability to water and de-icing salt, thus better protecting the embedded steel reinforcements (rebars) from corrosion.
Federal Bridge Corporation Ltd. (FBCL), owner of the Cornwall bridge and a partner in the development of the high-performance concrete, was so confident in the new product's performance that the decision to use it for the new bridge was an obvious choice.
Serving road warriors better
Finding just the right mix of ingredients involved a complex process of experimenting with various concrete technologies and proportions of special sands, coarse aggregates, cement, chemicals and water and then lab- and field-testing the various iterations. With input, support and expertise from public- and private-sector partners such as FBCL, Transports Québec, the National Capital Commission and the City of Ottawa, as well as W.R. Grace, Lafarge North America and Northeast Solite, the new concrete delivers countless benefits to the construction industry, bridge owners and travellers alike.
"For this project, we decided to focus on bridges because their lack of durability can be both costly and disruptive if repairs are not addressed in a timely manner," says Daniel Cusson, Senior Research Officer with NRC's Critical Concrete Infrastructure (CCI) program. "When a bridge is under repair, it can often cause delays or detours for travellers trying to get to their destinations and trucks trying to meet delivery deadlines."
In the two years since it has been installed, the concrete has yet to show any measurable cracks or shrinkage that are typically observed on high-strength concrete bridge decks. "NRC was instrumental in supervising the mixing of the concrete to ensure that the ingredients were always correct and the conditions for placing it were just right" says Glenn Hewus, FBCL's Senior Vice-president.
Bridging longevity and cost
In addition to creating a top-quality product, the multi-disciplinary partnership has successfully developed a practical solution for improving critical transportation infrastructure in Canada and beyond. The durability, strength and safety of the new concrete will also cut maintenance time and costs for both bridge owners and taxpayers.
Hewus points out that while high-performance concrete is nothing new, the NRC formulation comes in at a considerably lesser cost over its lifecycle than the concrete produced by other manufacturers. "While ours is still about 20 per cent more expensive than traditional concrete, the cost savings generated by its longer lifespan will not only save money in the long run, but also provide a faster return on investment—within five to seven years."
With cost and technical advantages over other high-performance concrete on the market, NRC's product is now being considered for projects by other bridge owners across Canada. "NRC provides an important engineering service to our country that reaches across borders" says Hewus. And the remarkable results of this first installation are a clear indication that this new solution can in fact go the distance.