Refinement of clay activation methods for enhanced reactivity

The production of “green” infrastructures made of concrete goes generally through the use of supplementary cementitious materials (SCMs), which decreases the carbon dioxide footprint due to reducing the Portland cement content needed for the production of the concrete. However, limitations on the availability of the major SCMs such as slag or fly ash are expected in the near future. Moreover, some common SCMs like silica fume or metakaolin are not only expensive but can also not be used in large proportions because it would affect negatively the early properties of fresh concrete.

Those limitations brought a lot of attention to clays in recent years. Clays have not been used to their full potential as cement constituents due to an ample supply of other SCM in the past. It is known that these materials exhibit pozzolanic properties when activated (by e.g. calcination) and can react with the calcium hydroxide of the cement. The energy consumption and CO₂ emissions during the activation of clays are lower than in cement production. Therefore, the substitution of a fraction of Portland cement by calcined clays will improve the sustainability of a blended binder.

Different activation methods are investigated in the project. Although calcination is more effective for some clay minerals and grinding for others, the temperature, time, energy input must be optimized for each specific clay to achieve its full potential. The project proposes to investigate and refine the activation methods on several Swedish clays, especially illitic, and reach a systematic understanding of the relationship between the activation method, activation mechanism, reactivity and properties of the cement-based system.