UC Berkeley
retrofits take "green" approach to concrete foundations
27
Dec 2000
By
Kathleen Maclay, Media Relations
Berkeley
- New foundations for the seismically retrofitted Wurster
and Barker halls at the University of California, Berkeley
are so "green" they'll save the pollutant-emitting equivalent
of 1.5 million vehicle miles, or 60 car trips around the Earth.
The foundations
incorporate high-volume fly ash concrete which requires far
less fossil fuel to produce than conventional concrete. Fly
ash is a byproduct of coal-burning power plants. The ash is
created at high temperatures and becomes tiny, beady glass
particles. Of the 60 million tons produced every year in this
country, about 75 percent of fly ash is trucked off to landfills
rather than converted into building material.
But enthusiastic
design and construction teams working on UC Berkeley seismic
projects say that the high-volume fly ash concrete mixture
reduces environmental impacts and can save money while producing
more durable concrete structures.
"Our main
goal in these projects is to make sure that hose who study
and work in these buildings will be safe in the event of a
major earthquake. That we can do so in such an environmentally
friendly way is a wonderful bonus," said UC Berkeley Chancellor
Robert M. Berdahl.
The projects
are signs of the progress of "green" building techniques.
"The sustainable
design movement is really taking off," said Wurster Hall retrofit
architect Scott Shell of EHDD Architects in San Francisco.
"We're excited that an institution such as UC Berkeley is
willing to be a pioneer in this effort."
Every ton
of standard cement produced for concrete requires about 1.5
tons of raw materials. Project architects and engineers said
standard cement also requires intense use of fossil fuel,
so much so that its production worldwide accounts for about
8 percent of all carbon dioxide emissions from human sources.
That is the equivalent of 330 million vehicle miles or 330
million pounds of carbon dioxide, the primary greenhouse gas
causing global warming.
Using fly
ash in nearly 1,800 cubic yards of concrete at Wurster Hall
will spare some of the greenhouse gas emissions that would
have resulted from producing conventional concrete. Wurster
Hall is home to the College of Environmental Design. The project
there represents pollutant savings in the use of cement the
equivalent of 650,000 miles behind the wheel of a car, said
Afshar Jalalian, a structural engineer with Rutherford & Chekene
Consulting Engineers of Oakland.
About 2,500
cubic yards of 50 percent fly ash concrete will be also poured
for foundations at Barker Hall as well, with comparable cost
and environmental savings.
The two
projects are part of the campus's on-going SAFER program,
a multi-year $1 billion-effort to seismically strengthen more
than a quarter of all buildings on the central campus to improve
life safety in the event of a major earthquake.
Shell has
been interested in sustainable design for about 10 years.
He encouraged the university to request bids for fly ash concrete
when planning the Wurster retrofit for both the performance
and environmental benefits. The bid came in $13,000 less than
standard concrete.
Although
50 percent fly ash concrete has been used for close to 15
years, it remains more popular in Canada than the U.S., where
it remains less known. In California, cement with 15 percent
fly ash is typical and the California Department of Transportation
now requires 25 to 35 percent fly ash because of the improved
performance benefits, Shell said.
The changeover
to fly ash takes perseverance, he said, but even so, "It's
not nearly as difficult as convincing 330 million people to
stop driving."
Shell praised
College of Environmental Design Dean Harrison Fraker and the
college's faculty for being so supportive of sustainable design
and informed about it. UC Berkeley also is home to the one
of the world's leading experts in fly ash concrete, P.K. Mehta,
a professor emeritus of civil engineering.
"When you're
doing something new and different, the burden of proof is
on you and you really need a team to make it work," Shell
said.
EHDD used
high percentages of fly ash in earlier projects, including
for the tanks of the Monterey Bay and Long Beach aquariums,
but Wurster Hall is its largest project so far using 50 percent
fly ash, Shell said.
Crews poured
600 cubic yards of the fly ash mixture, or 400,000 pounds
of fly ash plus cement, for the Wurster Hall foundations in
November. Another approximately 700 cubic yards of the high-volume
fly ash concrete will be poured on Friday (Dec. 29).
At Barker
Hall on the northwest end of the campus, plans call for pouring
the high-volume fly ash cement starting in April. Forell Elsesser
Engineers of San Francisco has used the "green" concrete-mix
in other projects, but this is its largest as well. The firm
also plans to use fly ash for the foundations of a lab at
UC San Francisco's Mission Bay campus.
"My hopes
are that these efforts will set the standard for similar projects
elsewhere," said Langston Trigg, UC Berkeley's associate vice
chancellor for capital projects. "Successful dissemination
of information about this approach and technology could have
a significant effect on our environment."
Extensive
tests on the UC Berkeley work are providing important data
about fly ash performance that will encourage more architects,
contractors and concrete makers to start using these concrete
mixes, according to Shell.
With satisfactory
bids for the material, crews then conducted a special trial
batching and testing of the mixture as a quality control measure,
said Jalalian, the structural engineer. There was additional
testing involving trial casting on a small area to allow the
contractor to become familiar with how the material sets after
it is cast.
One drawback
of fly ash is that it takes longer to gain strength and harden,
which needs to be accounted for in the planning stages of
any project, he said. Another sensitive consideration has
been color, but Shell said that's a minor problem.
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