Effect of gypsum on mortar strength of compound cementitous material compounded with clinker and limestone powder and coal ash

Different types and dosages of gypsums are selected in compound cementitous material compounded with clinker and limestone powder and coal ash. It is found that the flexural and compressive strength of compound cementitous material adding calcium sulfate dihydrate containing 46% SO3 at different age is higher than that of compound cementitous material adding plaster stone containing 33% SO3 when the mixture dosage and gypsum dosage are the same. The flexural and compressive strength of compound cementitous material including 3.2% SO3 at different age is higher than that of compound cementitous material including less SO3 when the mixture dosage and type of gypsum are the same. Sufficient content of SO3 is key point when compound cementitous material including plenty of mixture is prepared. Types and dosages of gypsum should be selected carefully.