Scientists develop alternative cement with low carbon footprint

Researchers at the Martin Luther University Halle-Wittenberg (MLU) in Germany and the Brazilian University of Para have developed a climate-friendly alternative to conventional cement. Carbon dioxide (CO2) emissions can be reduced during production by up to two thirds when a previously unused overburden from bauxite mining is used as a raw material. The alternative was found to be just as stable as the traditional Portland cement. The results were published in Sustainable Materials and Technologies.

Houses, factories, staircases, bridges, dams - none of these structures can be built without cement. According to estimates, almost six billion tonnes of cement were produced worldwide in 2020. Cement is not only an important building material, it is also responsible for around eight per cent of manmade CO2 emissions.

"Portland cement is traditionally made using various raw materials, including limestone, which are burned to form so-called clinker," explains Professor Herbert Pollmann from MLU's Institute of Geosciences and Geography. "In the process, the calcium carbonate is converted into calcium oxide, releasing large quantities of carbon dioxide." Since CO2 is a greenhouse gas, researchers have been looking for alternatives to Portland cement for several years.

One promising solution is calcium sulphoaluminate cement, in which a large portion of the limestone is replaced by bauxite. However, bauxite is a sought-after raw material in aluminium production and not available in unlimited quantities.

Together with Brazilian mineralogists, the MLU team has now found an alternative to the alternative, so to speak: They do not use pure bauxite, but rather an overburden: Belterra clay. "This layer of clay can be up to 30 metres thick and covers the bauxite deposits in the tropical regions of the earth, for example in the Amazon basin," explains Pollmann.

"It contains enough minerals with an aluminium content to ensure good quality cement. It is also available in large quantities and can be processed without additional treatment." Another advantage: The Belterra clay has to be removed anyway, so it does not have to be extracted only for cement production.

Even though cement cannot be entirely produced without calcium carbonate, at least 50 to 60 percent of the limestone can be replaced by Belterra clay. The process has another environmentally relevant advantage: the burning process only requires 1,250 degrees Celsius - 200 degrees less than for Portland cement.

"Our method not only releases less CO2 during the chemical conversion, but also when heating the rotary kilns", says Pollmann. By coupling these effects, CO2 emissions can be reduced by up to two thirds during cement production.

In extensive laboratory tests, the mineralogists were able to prove that their alternative cement meets all the quality requirements placed on traditional Portland cement.

Further research projects will now investigate whether there are also overburden sources in Germany suitable for cement production. "Raw materials containing clay minerals with a lower aluminium content could be used particularly in construction projects where lower-grade concrete is sufficient," explains Pollmann. "There is still huge potential here to further reduce carbon dioxide emissions."

Research Report: "Production of low- CO2 cements using abundant bauxite overburden Belterra Clay"

Related Links
Martin-Luther-University Halle-Wittenberg
Space Technology News - Applications and Research

Tweet

Thanks for being there;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Monthly Supporter
$5+ Billed Monthly

paypal only

SpaceDaily Contributor
$5 Billed Once

credit card or paypal

High-speed camera captures a water jet's splashy impact as it pierces a droplet
Boston MA (SPX) Aug 19, 2021
Squirting a jet of water through a drop of liquid may sound like idle fun, but if done precisely, and understood thoroughly, the splashy exercise could help scientists identify ways to inject fluids such as vaccines through skin without using needles. That's the motivation behind a new study by engineers at MIT and the University of Twente in the Netherlands. The study involves firing small jets of water through many kinds of droplets, hundreds of times over, using high-speed cameras to capture ea ... read more