Anhydrite powder is a new type of admixture used in concrete constructions.However,anhydrite powder can not be added in the fresh mixture alone but should be with other minerals supplementary additives like slag,which is supposed to be with potential activity of chemical reaction.In this paper,the effect of anhydrite powder on activating slag to take part in hydration of cement was investigated under different curing conditions from the mechanical strength of the mortar specimens.