'Green' concrete could be game-changer for construction industry
Microscopic flakes of graphene add strength and durability — but also raise cost and safety concerns.
Scientists have been tinkering with concrete in an effort to improve upon the world's most widely used construction material — and they’ve notched some notable successes.
New forms of concrete can trap and store the greenhouse gas carbon dioxide, break down pollutants from exhaust fumes, and help protect aging infrastructure by sealing cracks as they form. And now scientists in the U.K. have developed a “green” concrete that they say is more environmentally friendly than the ordinary stuff, as well as more durable and more than twice as strong.
“We were not expecting it to be that strong,” said Prof. Monica Craciun, a professor of nanoengineering at the University of Exeter and a member of the research team responsible for the new material. She called the material an "absolute game-changer" in a written statement and said a university-affiliated startup to sell it could be launched by year-end — although other experts gave a more measured assessment of the material's immediate commercial potential.
The new form of concrete looks like ordinary concrete but gets its special properties from the addition of microscopic flakes of graphene, a form of carbon that is one of the world’s strongest materials. Greater strength means less of the stuff would be needed to construct walls and other structures. That’s significant since making cement — concrete’s principal ingredient — accounts for 5 percent of global emissions of the greenhouse gas carbon dioxide.
And if walls and other components of buildings can be made thinner, new design possibilities open up for architects and builders who work with concrete.
Craciun said the concrete-graphene composite is four times more resistant to water infiltration than ordinary concrete — suggesting that buildings and infrastructure made of it might stand up better over time, especially in flood zones. The composite material is also more elastic than ordinary concrete, meaning it might be a better choice for construction projects in areas prone to earthquakes.
And as a better conductor of electricity than its conventional counterpart, the composite material might find surprising new applications. Craciun envisions roadways whose surfaces could be electrified so they heat up to melt snow and ice.
Low-Carbon Cement Gains Ground in Non-US Markets
A new type of cement that is based on a blend of limestone and calcined clay is gaining acceptance in developing countries and is expected to be commercially produced next year in South America. It is tolerant of impurities in its components, competitive in performance and economics with ordinary Portland cement and can reduce carbon dioxide emissions by up to 30%.
Limestone Calcined Clay Cement (LC3) has been developed by an international team of researchers coordinated by Nanocem, Lausanne, Switzerland, a consortium of academic and industrial partners for research in cement and concrete.
CO2 reduction sets LC3 apart from ordinary Portland, says Steven Kosmatka, vice president for research and technical services at the Portland Cement Association. “Calcined clay systems have been used in the U.S., but they didn’t take off,” he says. Blended cements are “great cements,” he adds, but only about six state departments of transportation accept performance-based cement. Wide U.S. adoption of low-carbon cement would require a change in society to value CO2 reduction more highly, he says.
But outside the U.S., CO2 reduction is a priority. In March, the World Business Council for Sustainable Development issued the Technology Roadmap for Low-Carbon Transition in the Cement Industry. “They forecast by 2050 [calcined-clay and limestone blends] will make up 27% of all cement made in the world,” says Karen Scrivener, Nanocem’s founder and director of the Laboratory of Construction Materials.
