Impact of using calcined clays in concrete

Calcined clays have been used as mineral additions in concrete for over decades. The product “metakaolin” is known to improve performance of concrete. However, this product is made of pure calcined clays, which are expensive. Recent developments have proven that lower grade clays can have a similar effect, for a much lower price, and if combined with limestone, the effect is enhanced.

The current paper describes the impact of using low grade calcined clays as mineral additions to concrete, either combined with limestone or not. Another option would be to use a cement containing calcined clay and limestone, with clinker content around 50%. Cement consumption per cubic meter of concrete is reduced, and the mechanical performance is improved at all ages. Calcined clays have also a beneficial impact on durability, with special emphasis on concrete exposed to marine conditions. The paper will discuss results of concrete made with industrially calcined clays, with properties like the clays most likely to be found in the Russian Federation.