A new form of green cement developed in Switzerland has the potential to reduce the carbon footprint of concrete by as much as 40 per cent.

Cement, a vital ingredient in modern concrete, accounts for nearly a tenth of humanity’s carbon dioxide emissions. The replacement of the Portland cement most commonly used in the manufacture of concrete is considered a key means of reducing greenhouse gas emissions, particularly given that the production of single ton of the material releases as much as 800 kilograms of CO2.

While a number of materials are already used to adulterate concrete mixtures in order to reduce their cement content, such as the fly ash produced as an industrial residue by coal-fired power plants, they do not exist in sufficient abundance to serve as a fully viable alternatives.

Researchers in Switzerland believe they may have stumbled upon the solution, however, in the form of a new cement comprised of readily available materials which can be added in large amounts to concrete mixtures without compromising the performance of the final product.

According to Karen Scrivener, head of the Construction Materials Laboratory at Switzerland’s Ecole Polytechnique Federale de Lausanne (EPFL) and principal investigator of the project, the cement consists of a mixture of calcined clay and ground limestone. When the two materials are combined together the aluminates from the calcined clay interact with the calcium carbonates from the limestone to produce a cement paste which is less porous and thus significantly stronger.

In the past, both calcined clay and ground limestone have been used as adulterating materials for cement in mere fractional amounts. The research team led by Scrivener has discovered, however, that these materials can comprise up half of the cement mixture without having an adverse impact on the physical properties of the final product.

Karen Scrivener

Karen Scrivener

Scrivener’s team believes the Limestone Calcined Clay Cement (LC3) they have developed has the potential to become the benchmark material for low-carbon concretes. Unlike the materials currently used to adulterate concrete, supply shouldn’t be an issue, given that clay and limestone exist in ready abundance around the planet. Should the material be adopted on a global scale, it result in a significant reduction in CO2 emissions.

The robustness of LC3 has already been demonstrated by a pair of industrial scale pilot projects, one in India and one in Cuba, both of which saw the material readily integrated into pre-existing cement production lines.

The Swiss Agency for Development and Cooperation (SDC) has now lent its support to the project, providing funding for the further development and testing of the material.