A Wayne State University researcher has found a greener, less-expensive way to improve a product that essentially has been set in stone for a long time.
In June, Wayne State and NTH Consultants of Detroit jointly filed a utility patent for a product called Detroit Cement, developed under the leadership of H.C. Wu, Ph.D., associate professor of civil and environmental engineering in the College of Engineering.
The team says the new formulation, created with the help of a Phase I Small Business Innovation Research grant from the National Science Foundation to NTH, is more environmentally friendly and less costly than traditional cements, while exhibiting improvement in several key performance characteristics.
Cement manufacturing is considered the third-leading source of worldwide carbon dioxide (CO2) emissions, and Wu believes that’s not likely to change anytime soon.
“The rise of China’s and India’s economies, global climate change due to increased levels of CO2, and the aging infrastructure of the United States have together produced an ideal opportunity for introducing an innovative, performance-enhanced, green cement product,” he said.
The industry to date has been dominated by Portland cement, which comprises limestone, clay and gypsum and acts as a binding agent in concrete. Despite some small improvements over the years, Wu said, Portland cement’s basic ingredients and manufacturing processes have remained essentially unchanged since the mid-1800s.
“Since that time, most people have not given much attention to cement or concrete as a product in need of improvement,” Wu said.
Researchers say Detroit Cement is highly durable and stronger than Portland, and that it is more resistant to chemicals than Portland or magnesium cement, which is another alternative to traditional mixes. Detroit Cement is a magnesium/geopolymer hybrid, and its magnesium source is domestic, widely available and inexpensive.
The new technology also requires less energy and emits less carbon dioxide during the manufacturing process, requiring calcination temperatures of 650 to 900 degrees Celsius instead of the 1,430-to-1,650-degree range needed to make Portland cement.
Additionally, Detroit Cement is highly ductile, which researchers say usually means that structural components, such as bridge decks, have the ability to deform much more before breaking. As a result, they believe bridges built with Detroit Cement will be much more crack resistant, leading to longer service life and less frequent maintenance.
Like Portland cement, Detroit Cement can be mixed with water, sand and aggregate, and then cast into structural forms. And because Detroit Cement hardens faster than Portland, researchers say, it gains strength quickly.
While several companies around the world are racing to develop the first viable green cement formula for mass production, Wu believes the winner of that competition will not be determined by being first to market or greenest, but by introducing a formula with the correct mix of performance attributes.
“In our minds, being greenest is not even one of the top four considerations,” he said. “We believe that in order to achieve industry staying power, the winning green cement will successfully address all the important criteria, in the right order.”
He believes that entering something as large as the cement industry should be done in small steps into niche markets. The NTH/Wayne State team has selected shotcrete as its gateway, reasoning that Detroit Cement’s quick setting, fast initial strength, high ductility and other performance attributes make it an ideal fit.
Shotcrete describes a process of spraying wet or dry concrete through a large-diameter, highly pressurized hose, rather than the traditional method of pouring it from trucks. Shotcrete is best recognized for its use in swimming pools, zoo habitat rockscapes and large dome structures; less publicly visible applications include overhead/vertical repair or renovation, prefabricated building panels, slope stability reinforcements and tunnel linings.
NTH/Wayne State team members already have identified 12 clients with an interest in field testing their new product, including DTE Energy, the City of Detroit Water and Sewerage Department, the American Concrete Pipe Association and the American Shotcrete Association.
While researchers are excited about the possibilities for Detroit Cement, Wu said they aren’t interested in becoming manufacturers, a number of which already own and control raw materials and distribution processes.
“It has become clear that in order to successfully launch such a new green cement formulation, one must not unduly disrupt the dynamics of a well-established network,” Wu said.
Instead, the NTH/Wayne State team hopes to sell the technology to the nearly 5,000 U.S. companies that comprise an industry generating about $110 billion annually, and which are always seeking to invest in technologies that promise to improve efficiencies and lower costs.
“Detroit Cement can help manufacturers differentiate their existing products from the competition, significantly increase their profit margins and lower overall manufacturing costs,” Wu said.