THE MECHANISMS OF INFLUENCE OF A FINELY GROUND FILLER ON THE FORMATION OF CEMENT BINDER STRUCTURE

Abstract

Comprehensive information on the processes occurring at certain stages of hardening is required to control the structure formation of concrete in order to obtain materials with optimal properties. During hydration of filled binders, spontaneous dispersion of cement particles in water and subsequent structure formation, significant changes in the concentration and mobility of ions dissociated during hardening occur, as well as changes in the properties and composition of the liquid phase. As a result of this, studies of the electrical conductivity of setting cement systems make it possible to fairly accurately assess the processes occurring in them, to determine the time intervals of the corresponding stages of structure formation. This method is sensitive to changes in the water-binder ratio, the concentration and dispersion of the filler, the temperature of the mixture, and other factors that affect the setting rate. In this work, it was used to obtain additional information on the mechanisms of the cement stone structure formation, in particular, on the role of the true water-cement ratio when a finely ground filler is introduced into the binder. The objects of study were hardening cement-sand samples at various concentrations of filler (c = mb/mc = 60%, 120%) and grain size ratios (Rb/Rc = 1:3, 1:1, 3:1) during the first five hours after mixing, when phase transformations occur most intensively. The established features of the resistance kinetics are explained on the basis of existing conceptions of the binders structure formation. It is shown that the processes of structure formation are significantly affected by the effect of reducing the true water-cement ratio in the presence of a finely ground filler, which, together with its concentration and grain size ratio of the filler and cement, largely determines the specificity of the processes of binders structure formation, being one of the main mechanisms for improving their structure.