September 18, 2006

TESKEY CONCRETE COMPANY LIMITED That was then and this is now. The delivery method used by Teskey and other concrete producers isn’t the only thing that has changed in the past 50 years. Environmental considerations are among dramatic changes in the industry.

Environment

Product evolution greatly increases ‘green’ quotient

BRIAN BAKER

staff writer

toronto

A pale grey colour describes concrete or the multitude of structural designs into which it is molded, but the product’s evolution in the past 50 years has given it a more ‘green’ appearance.

As the industry uses varied combinations of aggregates, additions and recycling methods to adapt to environmentally-conscious government legislation, concrete has become much more complex than the sand, Portland cement and water base started by Joseph Aspdin in 1824.

“Everyone is thinking ‘green’ and yes, we are always looking for products that can be integrated that otherwise would not be used,” said José Raposo, quality control manager of Teskey Concrete Company Limited.

“There are more incentives if you use more recyclables in your concrete.“

José Raposo

Teskey Concrete Company Limited

The LEED green building rating system is incorporating concrete into an environmentally-sound points system, rewarding projects with points to reach Platinum Certification.

“There are more incentives if you use more recyclables in your concrete, than you get rebates,” said Raposo.

Some fiscal rebates include tax incentives for innovation, flow-through share incentives, tax credits for early adoption of environmental technologies, and refundable tax credits for capital investment in, or research related to, eco-efficient technologies.

“One of the reasons why we can produce 100 megapascals (MPa) in the concrete is because of the recyclables. We could not achieve such high MPa without supplementary cementing materials,” Raposo added.

A megapascal is the metric quantity for measuring pressure and strength in concrete.

The industry standard is 35 MPa, which is approximately 5000 psi in Imperial measurements.

In the early 1970s, it was near impossible to reach 35 MPa in concrete; with the reuse of waste materials from refineries, smelters and power plants, concrete has become a stronger product.

“Recyclables being the fly ash, the slags, silica fumes and they do benefit the concrete,” said Raposo.

Fly ash is a coal combustion product that electric generating plants paid to have taken away and disposed. Now, it is a valuable resource for the concrete industry, replacing Portland cement in stronger, higher rated mixes.

Slag is a by-product from ore refineries and smelters. Most common in the removal of waste in metal smelting. It also assists in temperature control and controlling re-oxidation in the product before casting.

Silica fume is a very fine powder that is a by-product found in electric arc furnaces after the production of silicon alloys. Also known as microsilica, the waste from high-purity quartz is up to 100 times finer than Portland cement.

“It fills all the voids that Portland cement leaves behind, and the more dense the product, usually a high stress rating,” said Raposo.

The process of reclaiming unused concrete in trucks is also practiced in the industry as a method of reusing materials. If the concrete is still in its plastic state, it is emptied from the trucks, placed on conveyors and separates the water from the aggregates.

By removing Portland cement from concrete in varying degrees, and adding substitutes, the mix can be controlled on many levels.

With added chemicals and waste products, concrete companies can minimize or maximize setting times, pour in the winter months, and provide a product that requires less labour while complying with environmental codes.

Print | Email | Comment