Could Greener Concrete Also Be Stronger?

Researchers at the Massachusetts Institute of Technology have found that portland cement can be manipulated to form stronger concrete that also poses less harm to the environment.

More than 20 billion tonnes of portland-cement concrete are produced globally each year, and cement production accounts for 5% to 10% of the world's industrial carbon-dioxide emissions.

“If we are to produce a better concrete that cracks less, then we need less cement,” says Roland Pellenq, senior research scientist at Cambridge, Mass.-based MIT and co-author of a new study published in the Sept. 24 edition of the scientific journal Nature Communications.

Cement is a mixture of calcium-rich minerals, such as limestone, and silica-based materials, such as clay, that are heated to 1,500°C and ground into a powder. The fuel needed to cook this material, coupled with its natural decarbonation, contribute to CO2 pollution.

Conventional cement forms a ratio of about 1.7 parts of calcium for every one part of silica. Adjusting that calcium concentration to 1.5 would save up to 60% of the carbon dioxide that existing cement production releases into the atmosphere while doubling the material's resistance to cracking, researchers say.

“This is a real step for a cement that creeps less and is more crack-resistant and, as a consequence, will decrease the CO2 impact of this industry,” says Pellenq.

One application for this stronger cement could be precast manufacturing, in which production can be tightly controlled, scientists say.

Shale fracking is another possibility. By lining wells with stronger cement, frackers could use a wider range of drilling media that pose fewer blowout risks and environmental hazards.

“The oil industry needs a crack-free cement,” Pellenq explains.

Concrete has become a serious topic of academic research as scientists, engineers and others look for ways to make better building materials and infrastructure that is less costly to maintain.

In another recent study, published in the September edition of the journal Urban Climate, scientists at Northeastern University in Boston discovered that conventional concrete could degrade faster during periods of aggressive climate change. Corrosion due to warmer weather, they found, could exceed industry standards within 65 years.

Source: ENR.constructon.com