Concrete Improvements

Posted on Thu Mar 27 2008

By: Hilary Feldman in Climate Change, Environment

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With construction booming across much of Canada, that accounts for a lot of concrete. In fact, it is one of the most common man-made materials on the planet. Concrete is used for buildings, roads, bridges, dams, and many other creations. It is currently in favour for various reasons, including its durability, ease of construction, and relatively low cost.

Ancient forms of concrete have been used for thousands of years. Notable constructions include the Shaanxi pyramids in China and parts of classic Roman buildings. Clay cement was also used in Assyria, Babylonia, and Egypt. Modern concrete is made from a mixture of Portland cement - a combination of calcium, silicon, aluminum, iron, and gypsum - as well as ingredients like fly ash, gravel, sand, and water. Depending on the use, concrete mixtures can take a variety of forms. The balance of strength, durability, shrinkage, and cost determines the exact formula. Admixtures, specific chemical additions, are used to modify concrete properties such as setting time and fluidity.

A Calgary-based company, Whitemud Resources Inc., is using kaolin to replace some of the Portland cement content. Kaolin is a white clay that can be used to manufacture metakaolin. The prospective benefits of metakaolin include increased concrete strength and reduced cost. In addition, the white kaolin composition results in lighter-coloured concrete, reflecting more sunlight and requiring less cooling in summer.

Cement manufacture is a industrial process that results in high levels of carbon dioxide emission, accounting for 5-10% of the global total each year. Each tonne of cement produces roughly one tonne of CO2, with Portland cement accounting for most of this contribution. Whitemud estimates that their kaolin-based product generates half the usual emissions, as well as requiring less water during the process.

Only a portion of the Portland cement can be replaced - up to 20%. Otherwise, key properties are changed. Kaolin-enhanced concrete is less well-understood, due to its more recent inception. Further research may demonstrate other beneficial aspects. But it certainly draws attention to some of concrete’s attributes. Given how much cement and concrete is used around the world, it would be sensible to explore ways to make both the materials and processes more efficient and environmentally sustainable.