Use of low-grade kaolinite clays in the production of limestone calcined clay cement

The suitability of two different low-grade kaolinitic clays and limestone locally available in Switzerland to produce a limestone calcined-clay cement at industrial scale was investigated. Firstly, the clays characteristics related to reactivity were presented. Then, the effect of calcined clays on cement performance was explored according to EN 197-5 and EN 197-1 requirements. Finally, the new cement was produced at industrial scale by using a Swiss cement plant equipped with a Lepol kiln for clay calcination and clinker production and used to manufacture 3 different concretes mixes for 3 different environmental exposure classes (EN 206). The concrete mixes were tested for mechanical and durability performance. The results show that the two calcined low-grade clays are suitable to produce a limestone calcined-clay cement classified as CEM II/C-M (Q-LL). Moreover, all the 3 concretes manufactured with the new cement meet the minimum mechanical and durability standard requirements of the corresponding exposure classes.