Rheological properties of cement systems modified with mineral and plasticizing additives

Introduction. In practice, it is required to obtain mixtures both of equal workability, estimated by standard technical indicators (cone sediment, spreading, etc.) and of different rheological characteristics. Diluent additives effectively reduce the yield strength and viscosity, however, the effect of mineral additives in combination with organic surfactants on the rheological parameters of cement dispersions has been poorly studied. The paper is devoted to the study of this issue.Research methods. Finely dispersed quartz (Sud=340 m2/kg) and marble (Sud=320 m2/kg) obtained by grinding in a laboratory mill were used; binder CEM I 42.5 H of Oskolcement CJSC (tn.cw=230 min; НГ=26 %, C3S=61,59 %, C2S=14,2 %, C3A=6,83 %, C4AF=3,73 %); superplasticizer Polyplast SP-1, hyperplasticizer Sunbo 2021. Rheological parameters of cement dispersions were determined at low shear rate gradients έ up to 25 sec-1, which makes it possible to ensure the similarity of flow in laboratory and real conditions.Results. It has been established that pure and mixed cement dispersions without diluent additives are rheologically complex bodies with the highest shear stress and plastic viscosity. Mineral modifiers in combination with plasticizing additives effectively reduce plastic viscosity and shear stress, and their flow transitions to the Newtonian fluid regime with a viscosity independent of the shear rate gradient. Rheological parameters without additional mixed cement dispersions depended on the type of mineral filler. At the same time, with the introduction of diluent additives, dosages and the chemical base of additives have a predominant effect on rheological parameters.Conclusion. Mixed cement-marble and cement-quartz dispersions with the introduction of diluting additives are characterized by higher fluidity than cement dispersions. The introduction of plasticizing additives at certain dosages makes it possible to completely remove non-linearity, and the use of mineral fillers enhances the effectiveness of surfactants.