Belterra clay could replace limestone in cement production

In a study, funded partly by the Brazilian Ministry of Education, Martin Luther University Halle-Wittenberg (MLU), Germany, and Brazil’s University of Pará, have found that CO2 emissions can be reduced during cement production by up to two-thirds by adding Belterra clay, unused overburden from bauxite mining.

"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 Professor Herbert Pöllmann of MLU’s Institute of Geosciences and Geography. "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."

At least 50-60 per cent of limestone can be replaced by Belterra clay, which provides several advantages when compared with limestone quarrying. The clay has to be removed anyway, so it does not have to be extracted only for cement production. Furthermore, the burning process only requires 1250˚C – 200˚C less than for Portland cement.