Calcined clays are promising sustainable alternative materials for cement production. By calcining natural clay minerals (usually 600–900 °C), they become reactive and can be used as a partial replacement for Portland clinker in cement production. This results in a lower carbon footprint and reduced energy consumption in the production process.
Replacing cement clinker with so-called supplementary cementitious materials (SCM) such as fly ash and blast furnace slag has been done for several decades. Calcined clays have also been used, mostly in the form of metakaolin, which significantly improves the strength and durability of mortar and concrete. However, its limited availability and high cost restrict its practical application to a few specialist applications.
In comparison, 2:1 clay minerals such as illite or smectites are more widely available and economically attractive due to their lower costs. Recent research has explored the use of calcined 2:1 clay minerals as SCM, but their properties and efficient production are still not fully understood.
In the present work, different clays from Germany are characterized and tested as potential calcined clay. Besides conventional calcination using a rotary kiln, fluidized bed calcination is used to improve the reactivity of the calcined clays while being less time-consuming and therefore more energy efficient.