INFLUENCE OF MECHANICAL ACTIVATION ON THE PROPERTIES OF CEMENT-WATER COMPOSITIONS WITH THE ADDITION OF GROUND LIMESTONE

The paper considers the issue related to determining the effect of mechanical activation of a mineral binder on the properties of both hardening and hardened cement-water compositions. The mechanical activation of cement in combination with the consumption of ground limestone, the amount of which was adjusted in the range from 0 to 40 % of the cement mass, is relevant for this study. The effect of mechanical chemical activation of Portland cement only and Portland cement with the addition of 20 and 40 % ground limestone on changing the water-solid ratio of equiviscous compositions was studied. It was shown that mechanical and chemical activation of a cement-water composition has a positive effect on reducing the W/S ratio of equiviscous compositions from 0.42 (no activation) to 0.38 (activation period 180 sec). The obtained experimental results indicate the presence of an induction period of heating of the cement paste both on Portland cement not subject to mechanical activation (this period is approximately 6 hours from the moment of interaction of cement with water) and on Portland cement subject to mechanical activation. In this case, the induction period was no more than 2 hours. Joint mechanical activation of an aqueous mixture of Portland cement and ground limestone ensures acceleration of the hydration processes of the binder, which is confirmed by the intensification of the exothermic heating of the filled cement-mixing compositions. The positive role of mechanical activation is also reflected in the acceleration of the thickening rate of the compositions, which was recorded by the kinetics of the decrease in the diameter of their spread over time. The positive role of mechanical activation in reducing the effective viscosity of cement-containing compositions is confirmed, which ensures a decrease in their water-solid ratio by an average of ‒ 8 ... 10 %. A positive effect of mechanochemical activation of Portland cement with the addition of ground limestone on the strength of cement stone at the age of 3 days has been revealed. Experimental studies indicate that only due to mechanical activation the strength of samples made of cement stone with the addition of ground limestone can be increased by almost 25...30 %.