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The composition of cement and concrete has provided insight on carbon emissions reduction.
The composition of cement and concrete has provided insight on carbon emissions reduction.
 









Research puts a ‘green’ spin on concrete

Recent research has led to a number of breakthroughs in building material production, including more durable and environmentally friendly cement mixes, and concrete that doesn’t require sand.

A consortium of Indian, Swiss, Cuban and Brazilian researchers are reportedly close to commercialising a new blend of cement that could reduce the carbon footprint of concrete by up to 40 per cent.

According to Switzerland-based École Polytechnique Fédérale de Lausanne (EPFL), which leads the consortium, cement production is responsible for almost 10 per cent of human carbon dioxide (CO2) emissions.

“With global demand for cement to double by 2050, driven by growing demand in emerging economies, such as India, China and Brazil, the need for low carbon cement is becoming more and more pressing,” the EPFL stated in a press release.

The consortium has now developed a new cement mix that considerably reduces the CO2 levels released during production by substituting half of the usual Portland cement used to make concrete.

In a press release, EPFL stated that each tonne of cement releases up to 800kg of CO2, and while substituting a large fraction of the cement was a “well established way to cut emissions”, it was previously hard to find alternative materials to use. However, the new mix incorporates calcined clay and limestone – both of which were said to be readily available in many quarries and which might even result in a stronger concrete.

“When used together, the aluminates from the calcined clay interact with the calcium carbonates from the limestone, leading to a less porous, and therefore stronger, cement paste,” EPFL explained in the release. “While in the past, these materials have been used individually to replace a small fraction of the cement, together, they can replace up to half without altering the performance of the final product.”

It has been reported that production of the new mix – which has been labelled LC3 for Limestone Calcined Clay Clinker Cement – requires less processing and capital investment compared to standard cement, making it economically attractive as well.

“The testing and application phase is over,” Swiss ambassador Linus von Castelmur told the Indo-Asian News Service (IANS). “Now it has to pass through a standardisation committee before it is accepted by the industries. The research which has been done will not be patent-protected but available to everyone.”

The researchers added that they hoped to see LC3 become the new “gold standard of low carbon cement, produced by all major cement companies”.

‘Greener’ cement at a molecular level
Researchers from the US Massachusetts Institute of Technology (MIT) and France’s National Center for Scientific Research have undertaken similar research into how to reduce CO2 emissions associated with cement production.

Through detailed molecular analysis of the structure of concrete, the researchers have found that this could be achieved by modifying the ratios of material used in its composition.

“Cement is made by cooking calcium-rich material, usually limestone, with silica-rich material – typically clay – at temperatures of 1500 degrees Celsius, yielding a hard mass called ‘clinker’. This is then ground up into a powder,” MIT explained in a statement.

“The decarbonation of limestone and the heating of cement are responsible for most of the material’s greenhouse gas output. The new analysis suggests that reducing the ratio of calcium to silicate would not only cut those emissions but would actually produce better, stronger concrete.”

MIT claimed that the new study showed that carbon emissions could be reduced by as much as 60 per cent, and that the resulting concrete would be two times as resistant to fracture as normal cement.

MIT senior research scientist Roland Pellenq said the next step in the study involved taking the analysis from the molecular level and scaling it up to apply to engineering scale applications, such as infrastructure and housing.

Plastic – the perfect sand alternative?
In addition, academics from India’s Goa Engineering College and the UK’s University of Bath have reportedly partnered on a two-year project that will aim to create a “green and sustainable” concrete by replacing its sand content with used and treated plastic bags.

IANS reported that a pilot study had already been undertaken in India to replace sand with 10 per cent plastic in concrete, however, this resulted in a “minor reduction” in the mix’s compressive strength.

It was said that the University of Bath would be using its facilities and equipment to address these durability issues.










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Tuesday, 22 October, 2019 8:11am
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