Granulated Blast Furnace Slag
Helps School Achieve Platinum

by Robert Carlsen

For a school complex to achieve a LEED platinum rating, every conceivable sustainable technique and product has to be used to its utmost viability.

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For the Chartwell Progressive School in Seaside, Calif., which is in the Monterey Bay area, even its concrete goes far beyond flyash in achieving green excellence.

As recommended by San Francisco-based EHDD Architects, the task of finding a suitable concrete substitute fell in the hands of the general contractor, Ausonio Construction, Inc., of Castroville, Calif. President Andrew Ausonio contacted its concrete subcontractor, Don Chapin Ready Mix Division of Salinas, which suggested ground granulated blast furnace slag in lieu of 100 percent Portland cement or flyash.

A Byproduct

Slag is 99 percent byproduct of the production of iron ore, which is usually sent to landfills. Substituting convention cement with slag reduces 70 percent of CO2 emissions released during the production of conventional cement.

This post-industrial, recycled product is recognized by the U.S. Environmental Protection Agency as a "recovered" product.

Since no other company locally or regionally was mixing slag cement, Ausonio asked his subcontractor to find a supplier. Don Chapin also agreed to purchase an extra silo to handle the 26,000-sq.-ft. campus project.

Lehigh Cement Co. of Concord, Calif., the supplier, had the history of environmental and sustainable efforts to make the project successful, said Ausonio. "We provided a stronger, less expensive material that helps Chartwell fulfill the requirements of LEED certification," said Ausonio.

The slag mixture was used in the foundations, lots and sidewalks.

"Ground granulated blast furnace slag is lighter-around 25 percent lighter-in color than regular cement," Ausonio said. "This also deletes the heat island effect and saves energy inside the building. This ambient reflection effect also requires fewer lighting fixtures inside the buildings."

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