Carbon-neutral cement made with industrial residue

Researcher at Martin Luther University Halle-Wittenberg in Germany found a way to produce more environmentally friendly and sustainable cement alternatives, made with industrial residues.

Cement is the main ingredient in concrete and also the material that makes concrete’s carbon footprint so large. This because cement’s basic raw material is limestone, which has to be converted into cement clinker in large furnaces. About a tonne of carbon dioxide is released during cement production for every tonne of limestone, most of which is emitted by the limestone itself.

In their search for alternative raw materials, the Halle researchers came across two types of industrial waste: residue from the production of kaolin and aluminium. The researchers tested these residues in various mixing ratios and analysed the physical properties of the new cements. The study showed that the two types of industrial waste can produce cement that has the same properties as traditional mixtures. The residual materials contain no carbon dioxide that could be released during further processing.

The residua waste can either be used on their own or to make cement mixtures with a lower ratio of limestone to make them more climate-friendly.

Unfortunately, the residual materials have one downside: there isn’t enough to fulfil the global demand for cement. However, the researchers are looking at other materials, like volcanic ash or mineral resources that have not been used yet industrially and that don’t release carbon as well, to replace limestone in cement production, such as various types of clay.

Photos: Martin Luther University Halle-Wittenberg