INFLUENCE OF ADDITION OF ULTRAFINE CEMENT ON THE RHEOLOGICAL PROPERTIES AND STRENGTH OF PORTLAND CEMENT PASTE

摘要

Mixing powders of different mean grain size at certain mix proportions may increase packing density of a powder. This conventional technique frequently used in ceramic production also can be applied to improve the properties of cementitious binders. This is generally done adding fine fly ash or microsilica to the coarser cement. In the presented paper the effect of mixing ultrafine cement and normal grain sized Portland cement, which results in a decrease of the porosity and hence an improvement of the mechanical properties of the hardened paste, is described. Additionally the rheological mix properties of the fresh paste are influenced positively, leading to a better workability. The influence of different mix proportions of ultrafi ne cement on the rheological properties and strength of Portland cement paste are studied. The experiments show an important dispersing effect, decreasing yield value and plastic viscosity. This permits mixing of very low w/c-ratio cement pastes with good workability applying conventional mixing procedures. Due to the filling effect and the resulting low water/binder-ratio, high strengths, especially flexural strength, can be achieved.