Mechanochemically activated clay as sustainable binder

High-temperature requirements, emission of hazardous substances from cement kilns and the significant CO2 footprint in the calcination step are factors requiring special attention in the cement industry. Local and commonly occurring clays can be a sustainable alternative for producing cementitious binders. Structural disorder in natural clay minerals can be induced through mechanochemical activation (MCA), by which the material develops an enhanced reactivity. The treatment of a Swedish natural clay through intensive grinding is carried out in order to assess its potential as a sustainable cementitious binder. Several grinding parameters influence a MCA product. The filling ratio of the jar, the rotation speed, the time of grinding, as well as wet and dry environment, are variated to optimize the MCA process. The MCA process doesnot require high temperatures or added chemicals and shorter processing times can avoid high-energy requirements during fine grinding. The structural changes of the clay were analysed by X-Ray Diffraction (XRD). Analysis of the particle size distribution of the raw and processed clay suggested a correlation with the grinding duration. An increased ratio of grinding media versus the amount of ground material, while longer grinding duration increased the overall efficiency of the MCA process. The strength activity index (SAI) indicated an enhanced pozzolanic activity for the mechanochemically processed clay. Compressive strength tests have shown a strong correlation between an enhanced amorphization rate and increased compressive strength values.