Abstract: A method for manufacturing calcined clays comprising extracting and mixing raw clays; dosing a reducing agent to the mixed raw clays and homogenizing the resulting mixture; reducing the particle size of the mixture to less than 10 mm; heating the mixture in a flash dryer or flash calciner until the mixture has between 0% and 5% moisture; calcining the dried mixture from 600 to 900° C., maintaining an oxygen concentration between 1 and 5%; and cooling the calcined clay from 900° C. to 120° C., and uses of such calcined clay resulting from the claimed method in cement and/or a cementitious material for preparing concrete.