NRC’s Institute for Research in Construction reports that it has been developing a 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.
Developed by Dr. Daniel Cusson, Ph.D., P.Eng., a senior researcher at the NRC Institute for Research in Construction (NRC-IRC) in Ottawa, the high-performance self-curing concrete minimizes shrinkage, which is typical of high-strength concrete, but maintains high-strength concrete’s excellent mechanical properties.
The new formulation also greatly reduces cracking, which diminishes the penetration into the concrete of agents such as chlorides from de-icing salts, thus reducing corrosion in the steel reinforcement.
Dr. Cusson says the concrete has undergone extensive testing in the laboratory and at NRC’s outdoor exposure site. Now, the Federal Bridge Corporation is considering using the new mix for one component of the replacement of the North Channel Bridge in Cornwall.
As described in the NRC/IRC newsletter Construction Innovation, March 2011 issue: “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. This porous sand can hold up to 20% of its own weight of water, which serves to cure the concrete uniformly from the inside, thus preventing self-desiccation.”
The unit cost of the new concrete is only 5% higher than that of standard high-strength concrete.
To see the article in Construction Innovation, click here.