Abstract: The claimed subject matter relates to a novel cement comprising Portland cement clinker and a supplementary cementitious material. The supplementary cementitious material comprises a heat treated clay material and an optionally heat treated carbonate material, wherein the clay material has been heat treated optionally together with the carbonate material in such a way that the heat treated clay material is substantially dehydroxylated while the optionally heat treated carbonate material remains substantially carbonated. This can be achieved by premixing the carbonate and clay materials before heat treating to 400-700 C, or heat treating the clay material separately to a temperature of up to 900 C. When used in the final application the cement results in much higher strengths than would be predict from any other combination of these materials.

Abstract: The claimed subject matter relates to a novel cement comprising Portland cement clinker and a supplementary cementitious material. The supplementary cementitious material comprises a heat treated clay material and an optionally heat treated carbonate material, wherein the clay material has been heat treated optionally together with the carbonate material in such a way that the heat treated clay material is substantially dehydroxylated while the optionally heat treated carbonate material remains substantially carbonated. This can be achieved by premixing the carbonate and clay materials before heat treating to 400-700 C, or heat treating the clay material separately to a temperature of up to 900 C. When used in the final application the cement results in much higher strengths than would be predict from any other combination of these materials.