Page 17 - October 2015 Green Builder Magazine

ALTERNATIVE CONSTRUCTION

Getting the 15
Carbon Out

Innovative redesigns of established construction materials and methods
may hold the key to lowering the embodied energy of buildings.

UNTIL RECENTLY, USING construction materials with IMAGE CREDIT: © JACOB SNAVELY www.greenbuildermedia.com 10.2015
high embodied energy has been viewed as “worth
it,” if those materials contribute to higher energy Local Sourcing. The color of the blocks comes from the locally
performance while the building is occupied. But as sourced mineralogy of the recycled aggregates. In this case, the
buildings become more energy efficient, construction rhyolite material is sourced from an adjacent quarry 200 yards
materials make up a greater proportion of the total carbon from the factory.
footprint.
Not surprisingly, we’re seeing more attempts to develop low- steam-curing. They are made by compressing aggregates—often
carbon alternatives to some commonly used building materials recycled or waste material— with reactive “geopolymers,” using
with high embodied energy, or at the very least, to replace some a specially designed hydraulic machine that utilizes levers to
of the content with “low-carbon” substitutes—spray foams with drastically increase the compressive force.
some percentage of bio-based materials, for example, or concrete in
which some of the Portland cement has been replaced with fly ash. Normally, the sand or gravel in concrete masonry units is
On the surface, the Watershed Block doesn’t look like a disruptive washed clean of the reactive fines.
building material. The blocks resemble cinderblocks, only more
colorful and varied, and they have the same dimensions as any “We’ve discovered the dust on this gravel, which is silt and clay
masonry unit. But Watershed Block, which is being developed by particles, is valuable,” says Easton. “The silt and clay work together
David Easton, Joe Dahmen and Dr. Jose Munoz, has the potential to bind particles together, and the material becomes very durable
to transform masonry construction into a low-carbon industry when compressed.” Easton’s team has experimented with different
that supports local communities. materials, searching for the best formulas of geopolymers from

COMING SOON: EARTH MASONRY UNITS continued on page 17
Concrete masonry units, or CMUs, are a versatile and speedy
construction material. But they contain Portland cement, the
manufacture of which requires extremely high temperatures.
(Manufacturing one ton of Portland cement creates approximately
one ton of carbon emissions.) Crushing the aggregate and cleaning
the sand and gravel components require additional energy.

By contrast, the Watershed Block contains half to none of the
Portland cement of regular CMUs, and the blocks don’t require