Вплив механохімічної активації композиційного цементу на міцність будівельного розчину

Abstract

The article discusses issues related to the use of technology for the production of mortar mixtures and mortars based on high-speed mixers, the operation of which causes mechanochemical activation of the binder. The rotary counterflow mill used in the work acts as an activator of the surface zone of both Portland cement grains and quartz sand grains and, thus, contributes to the intensification of the processes of structure formation of cement paste and mortar based on it. Based on the fact that one of the promising ways to reduce the cost of cement activation is to reduce the energy intensity of the dispersion process itself, the use of relatively low-energy rotary mills can be considered as an effective way to increase the activity of the binder. After the joint activation of Portland cement and unground quartz sand (the amount of which was adjusted from 0 to 50 % of the cement mass; activation period - 300 seconds), samples were made from equal-viscosity cement paste. It was experimentally established that the maximum strength of cement stone at 28 days of age was achieved when using composite cement with a 20 % content of activated sand. To determine the influence of the studied factors, such as the consumption of mechanically activated composite binder, the concentration of superplasticizer C-3 (0...1,5 %) and the consumption of microsilica (0...10 %) on the strength of the mortar in 2 and 28-day old, a 3-factor experiment was conducted. It was established that in the studied hardening period, the content of mechanically activated composite cement has the greatest influence on the compressive strength for the studied mortar compositions (from 1:3 to 1:1). The next most important influence on the strength of the mortar is the consumption of superplasticizer C-3. The increase in compressive strength of a mortar from the introduction of microsilica into its composition does not exceed 10-15 %. The combined effect of mechanical activation of the binder and the use of the C-3 additive ensures an increase in the strength of the mortar (mortar composition 1:1) at 28 days of age from 43,5 MPa (non-activated binder; no C-3 additive) to 63 MPa, that is, almost by 45 %. For a mortar of similar age with a lower consumption of composite cement (mortar composition 1:3), mechanical activation of the binder in the presence of 1,5 % C-3 additive ensures an increase in the compressive strength of the mortar from 21 MPa (non-mechanically activated binder; C-3 = 0 %) to 39 MPa.