PRELIMINARY ACTIVATION OF CEMENT-SAND MIXTURE IN ORDER TO INCREASE THE STRENGTH OF CONCRETE

Abstract

The article discusses an effective technology for producing concrete with increased strength. For this purpose, it is proposed to perform preliminary mechanical activation of cement with sand with natural humidity (5-8%) in an energized apparatus, which is a rotary-type centrif-ugal mixer-disintegrator. During mixing, cement hydration occurs with the formation of nanodis-persed hydration products on the surface of cement grains, which are stripped off withsand and enter the mixture. Thus, in the micro-volumes of the cement-sand mixture, there is a uniform dis-tribution of the fraction of nanodispersed particles –highly dispersed products, preliminary hydra-tion of cement. The activity of the resulting activated mixture during subsequent hydration was determined using a differential microcalorimeter with a water-solid ratio (V/T) equal to 0.2. Calo-rimetric studies have shown that the temperature change inthe cement-sand mixture proceeds sim-ilarly to pure cement in contact with water, but after the first induction period. The mechanism of interaction of cement with water in the sand mixture changes significantly, which is accompanied by an increase in the temperature difference of the material in the cells to 0.87-0.88 °C and this difference is maintained for a long period of time. This is explained by the fact that the formation of cement hydration products occurs not only due to the processes of cement hydration, but also additionally during the chemical reactions of the formation of calcium hydrosilicates during the interaction of activated nanodisperse products and quartz sand.The preparation of concrete using an activated cement-sand mixture with a large aggregate and an estimated amount of water can significantly increase the strength of concrete and its other performance characteristics.