Geoscientists from Martin Luther University Halle-Wittenberg (MLU) in Germany have discovered an environmentally friendly and sustainable alternative for producing cement.

The team of researchers discovered that the industrial residues left behind in the production of aluminum and kaolin can be used as environmentally friendly and sustainable substitutes for limestone, which is the basic raw material for producing cement. During the production of cement, which, according to the study, is responsible for roughly 8% of annual global carbon dioxide emissions, limestone is converted to cement clinker in large furnaces — a process that takes a substantial toll on the environment.

"Around one tonne of carbon dioxide is released during cement production for every tonne of limestone. The majority of this is emitted by the limestone itself," said Professor Herbert Pöllmann, a geoscientist at MLU.

As such, the team sought out alternatives that were both climate friendly and capable of producing high-quality materials. Using different mixing ratios, the researchers determined that the mixtures made with the industrial residues both produced cements with the same properties as traditional cements but without carbon dioxide that could be released upon additional processing. Similarly, the team discovered that both residues could produce large quantities of cement.

However, there are drawbacks to the process, according to researchers, "There aren't enough industrial residues to cover the global demand for cement," explained Pöllmann.

Consequently, researchers are looking at other natural products including volcanic ash or other mineral resources like certain types of clay that do not release carbon dioxide. Additionally, the team is exploring whether cement producers could use lower ratios of limestone in the production of cement while using the industrial residues to substitute for some of the missing limestone.

The research is published in the journal Construction and Building Materials.