CONDITIONS FOR THE OPTIMAL RE-COMPACTION MODE OF A CONCRETE MIXTURE AND CRITERIA FOR VIBRATION EFFICIENCY

Abstract

The article considers the conditions for the optimal re-compaction mode of a concrete mixture in a vibration machine with spatial excitation, in which the action of horizontal oscillations of the mould is combined with vertical oscillations of the surcharge device. The relevance of the study is обусловлена by the need to improve the efficiency of vibration compaction of concrete products, ensure intensive structural rearrangement of the mixture, and reduce energy consumption during the forming process. The aim of the study is to establish criteria for the efficiency of vibration re-compaction and to substantiate the parameters of the optimal operating mode of the installation based on an energy approach. The study uses methods of analytical modeling based on the energy balance over one oscillation cycle, determination of dissipated energy in the vertical and horizontal deformation channels, as well as formulation of threshold conditions for active compaction according to dynamic pressure and shear stresses. Relations were obtained that make it possible to assess the energy efficiency of the process, establish the conditions for coordinating excitation frequencies, and determine the synergy coefficient of the combined action of shear and compression mechanisms. It is shown that the optimal re-compaction mode is achieved under the condition of maximizing the energy dissipated in the mixture, fulfilling the threshold conditions for structural rearrangement of the medium, and maintaining a quasi-resonant mode while taking into account changes in the dynamic properties of the mixture during compaction. The practical significance of the obtained results lies in the possibility of using the proposed criteria to select the parameters of the surcharge device and the operating modes of vibration exciters in the design and improvement of vibration installations for forming concrete products.