Published on Monday February 20, 2012
Drexel University engineers have found a way to improve upon
ordinary Portland cement (OPC), the glue that's bonded much of the
world's construction since the late 1800s. In research recently
published in Cement and Concrete Composites, the group
served up a recipe for cement that is more energy efficient and
cost effective to produce than masonry's most prevalent bonding
Drexel's "green" variety is a form of alkali-activated cement
that utilizes an industrial byproduct, slag, and a common mineral,
limestone, and does not require heating to produce. According
to Dr. Michel W. Barsoum, A.W. Grosvenor
professor, this alternative production method and the ubiquity of
the mix ingredients, lessens the cost of materials for Drexel's
cement by about 40 percent versus Portland cement and reduces
energy consumption and carbon dioxide production by 97 percent.
"Cement consumption is rapidly rising, especially in newly
industrialized countries, and it's already responsible for 5
percent of human-made carbon dioxide. This is a unique way to limit
the environmental consequences of meeting demand," Dr. Alex
Moseson, one of the lead researchers on the project, said.
While forms of alkali-activated cement have been used as far
back as the 1950s and 1960s in several buildings in the former
Soviet Union, much of the inspiration for this research came from
the Pyramids in Egypt, as well as buildings in ancient Rome.
"Our cement is more like ancient Roman cement than like modern
Portland," Moseson said. "Although we won't know for 2,000
years if ours has the longevity of Roman buildings, it gives us an
idea of the staying power of this material."
In contrast to ordinary Portland cement, Drexel's cement is made
of up to 68 percent unfired limestone, a plentiful, cheap, and
low-carbon dioxide resource; American Society for Testing and
Materials' standards for Portland cement limit the amount to 5
percent. To this base, a small amount of commercial alkali chemical
is added along with the iron slag byproduct. In Portland cement the
substitute for this mixture, called clinker, is produced by firing
a number of ingredients in a kiln, thus requiring more energy and
generating more carbon dioxide.
During Moseson's work in India to commercialize the technology,
he developed products that meet local standards, using entirely
local materials and techniques. He also investigated how the
availability of green cement could help make quality building
materials more affordable and accessible to marginalized
populations living in slums, and create jobs by jump starting
small-scale cement manufacturing in the country.
"Our results and the literature confirm that it performs as well
or better than OPC," Barsoum said. "We are very close to
having the cement pass an important commercialization milestone,
ASTM C1157, a standard that judges cement-like products on
performance, such as strength and setting-time, regardless of
The next step for the cement is getting it to the market, which
the group is working toward via a start-up company called
Greenstone Technologies, Inc.
News about this research has appeared in The Daily Climate, Planet Forward, Climate Central, Cement Newsline of Cement
Americas magazine, Popular Mechanicsand Flying Kite. Moseson was also
interviewed for Living on Earth, Public Radio
International's environmental news magazine, which aired the week
of January 27, 2012.