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Abstract
The rheological properties of the cement pastes have been determined using a rotational viscometer under a special testing routine by increasing and retaining a steady rotation speed of the viscometer cylinder up to certain values and for a certain time. These tests, using rotational viscometer, have been conducted by making the assessment of cement paste flow curves, using Bingham rheological model. Rheological properties of cement pastes were tested at different times after pastes mixing: 0 min, 30 min, 60 min, 90 min, 120 min and 180 min. Cement pastes with same W/C ratio equal to 0.35 were tested. The content of admixture was used 0%, 0.5%, 1%, 2%, 3% and 5%. The admixture of Ca(NO3)2 can be used in cement pastes and concretes without a reduction in consistency during 120 min in the dosage of up to 2%. Dosages of Ca(NO3)2 from 3% are not recommended for cement pastes and concrete, they significantly increase the viscosity of mixtures immediately after mixing The admixture of calcium nitrate changes thixotropy of cement pastes. In this case, a bigger dosage of calcium nitrate increases the thixotropy of pastes.
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Notes on contributors
Gintautas Skripkiūnas
Gintautas SKRIPKIŪNAS. Prof., Dr, Head of the Department of Building Materials, the Faculty of Civil Engineering, Vilnius Gediminas Technical University (VGTU), Lithuania. Research interests: building materials science, concrete technology, rheological properties of the concrete mixtures, structure and properties of the concrete, durability of concrete, concrete modifications.
Asta Kičaitė
Asta KIČAITĖ. Assoc. Prof. at the Department of Building Materials, the Faculty of Civil Engineering, Vilnius Gediminas Technical University (VGTU), Lithuania. Research interests: building materials science, building materials durability, frost resistance of ceramics, rheological properties of the concrete mixtures, physical and structural properties of building materials.
Mindaugas Macijauskas
Mindaugas MACIJAUSKAS. PhD student at the Department of Building Materials, the Faculty of Civil Engineering, Vilnius Gediminas Technical University (VGTU), Lithuania. Research interests: structure and properties of building materials (binders, concrete, dry mixtures), durability, rheological properties, renewable resources in the production of building materials in the context of sustainable development.