Solidifying the Future
Concrete Innovations Across the Country Get the Job Done

By Robert Carlsen, editor of California Construction. The McGraw-Hill Construction publication can be read online by visiting www.california.construction.com

The Chartwell Progressive School in Seaside, Calif., is using ground-granulated blast furnace slag in lieu of Portland cement or flyash. The school hopes to achieve a LEED platinum rating.

Granulated Blast Furnace Slag Helps California School Go For Platinum
For a school complex to achieve a LEED platinum rating, every conceivable sustainable technique and product has to be used to its utmost viability. And for the Chartwell Progressive School in Seaside, Calif. (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.

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

The 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," Ausonio said.

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," said Ausonio. "This also deletes the heat island effect and saves energy inside the building. The ambient reflection effect requires fewer lighting fixtures inside the buildings."

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