In this study different clays were tested with various granular sizes and calcination parameters. The pozzolanic properties were investigated using metakaolin-lime mixtures by the evaluation of both the mechanical strength and combined lime. The mineralogical composition, particle size distribution and degree of amorphousness were the main factors affecting the pozzolanic activity of calcined clays. Influences of the pozzolanic activity on the mechanical and durability properties of concrete was established from test results on blended portland-metakaolin cements.