MECHANOACTIVATION OF PORTLAND CEMENT AND ITS INFLUENCE ON THE CHARACTERISTICS OF CONSTRUCTION COMPOSITIONS FOR VARIOUS PURPOSES

The issues considered in the article are related to determining the effect of mechanical activation on the properties of cement-water compositions and building mortars based on them. The activation of cement in combination with the use of ground quartz sand and the superplasticizer Relaxol-Super PC is relevant for this study. The amount of quartz sand was adjusted in the range from 0 to 40% of the cement mass, and the superplasticizer (0,15 – 1,5%) of the binder mass. The use of this technology ensures acceleration of cement hydration processes, maintaining the required level of composition mobility with a lower consumption of mixing water, and intensification of exothermic heating. The presented experimental data made it possible to evaluate the effect of the binder activation period and the superplasticizer consumption on the flow of the aqueous cement-containing composition. It was found that the main contribution to the decrease in the water-solid ratio (provided that equiviscous compositions are obtained) is achieved by activating the cement-containing composition for 180 sec. with the addition of 1,5% superplasticizing additive. The water-solid ratio decreases by more than 50%. A further increase in the amount of plasticizer has low efficiency and has little effect on decreasing the water-solid ratio. Activation in combination with reduced water hardening of the cement-water composition contributes to both an increase in the heating intensity and an increase in its maximum temperature. After activation, the maximum temperature increased by 5-11% compared to the non-activated cement-water composition. The peak of the exothermic reaction for the mechanically activated cement-water composition occurs 3 hours earlier compared to the non-activated mixture. The increase in the strength of the mortar on mechanically activated cement with the addition of a superplasticizing additive reached 71% compared to the control.