Measurement of viscosity during vibroextrusion of fiber concrete

Currently, the rheological properties of cement mortars containing dispersed reinforcement have not been studied enough, so it is important to develop a method for measuring the viscosity of fiber concrete mixtures that would simulate the technological process. To consider the flow process and calculate the rheological characteristics of fiber concrete mixtures during vibroextrusion, hydrodynamic theories were applied due to the fact that these mixtures behave like liquids in a vibration field. When solving flow problems, it is taken into account that vibrating fiber concrete mixtures are Newtonian systems. To obtain objective rheological characteristics of fiber concrete mixtures, it is proposed to measure viscosity directly during vibro-extrusion molding of flat products. The peculiarities of the flow of Newtonian fluids between flat fixed walls, which converge in a flat symmetrical rectangular narrowing channel, are considered. It is proposed to determine the reduction of the flow rate of the mixture in the rectangular channel compared to the flow between the plates by the braking coefficient. A graph of the dependence of the braking coefficient on the ratio of the sides of the cross section of the rectangular channel is plotted. 2 formulas are proposed for calculating the braking coefficient. The comparative analysis of the proposed formulas gives a good convergence of the calculation results, the average approximation error is equal to 0.0126%, which indicates a high level of coincidence of the regression equation with a more complex analytical formula. Taking into account the inhibition of the liquid flow in the end zones of the rectangular channel, a formula was proposed for calculating the viscosity of the fiber concrete mixture during the formation of flat products in the narrowing vibroextruder channel. The calculation formula contains the geometric dimensions of the channel, the density and the flow time of the fiber concrete mixture, and to determine the viscosity of the mixture, it is necessary to measure only the time of its complete flow during vibroextrusion. The proposed formula and methodology for calculating viscosity can be used to determine the rheological characteristics of any Newtonian fluids using a flat symmetrical rectangular narrowing channel. In the future, it is planned to continue researching the properties of fiber concrete mixtures under the influence of vibration.