INFLUENCE OF CEMENT PROPERTIES ON RHEOLOGY OF FRESH CEMENT MORTARS WITHOUT AND WITH SUPERPLASTICIZER

Sine qua non in workability of cement binder mixtures (mortars and fresh concretes) designing is the knowledge of the relationships between composition and constituents characteristics, and rheological parameters of mixture. Until recently the influence of cement properties on rheology of cement binder mixtures was considered to be of minor importance. At presents a number of research proves, that influence of cement properties on cement binder mixtures rheology may be significant. The paper present results of investigation on influence of cement specific surface, C(3)A, Na(2)Oeq and SO3 content in cement on rheological properties of mortars without and with different type superplasticizers addition. In order to obtain unequivocal relations, laboratory prepared cements were used. Rheology results have been evaluated according to the Bingham model. It was stated in literature that the relationships obtained for mortars can be used in controlling the workability of both mortars and fresh concrete. It was determined that rheological properties of mortars depend successively on: C(3)A content in cement, specific surface of cement, Na(2)Oeq content in cement and interaction of these factors. No considerable influence of SO3 content in cement on rheology of mortars was observed. The basic trends of influence of investigated cement properties on rheology of mortars are presented and discussed. The regression models of influence of cement properties on rheological parameters of mortars were developed. These models may be applied to choose appropriate cement or cement - superplasticizer from the workability point of view and what is more for designing workability of fresh cement binder mixtures.