Vestnik MGSU (Apr 2024)
Modelling the influence of mass transfer parameters on the kinetics of corrosion interaction of concrete and biological media
Abstract
Introduction. The impact of microorganisms on the cement stone of concrete accelerates the removal of “free calcium hydroxide” from the pore structure and promotes the decomposition of calcium-containing phases, resulting in a decrease in the strength characteristics of concrete and further destruction. Biodegradation must be taken into account when determining the durability of concrete. Mathematical modelling makes it possible to predict its condition at any stage of the life cycle of a concrete product and to establish its remaining service life.Materials and methods. The effect of mass transfer parameters on changes in calcium hydroxide concentrations in concrete and on the intensity of its leaching into a liquid medium is shown graphically by the results of numerical modelling. The description of mass transfer processes in concrete biocorrosion was carried out using a developed mathematical model, which takes into account the influence of microorganisms and their waste products as an internal source of absorption or release of mass of “free calcium hydroxide” in concrete cement stone. The conditions for reaching the values of calcium hydroxide concentrations in cement stone corresponding to the beginning of decomposition of highly basic components are described by solving the mass transfer problem.Results. Based on the mathematical model describing the kinetics of mass transfer, a mathematical apparatus for predicting the degree of biodegradation of cement concrete was developed. Graphical dependences are presented, which are the result of a simulated numerical experiment, describing the effect of similarity criteria (Fourier, Bio) and a coefficient taking into account phase characteristics on the dynamics and kinetics of the mass transfer process during concrete biodegradation in a wide range of system parameters. The most intense change in the kinetics and dynamics of mass transfer occurs at the initial stages of exposure to the products of microorganisms during liquid corrosion of concrete.Conclusions. The obtained graphical dependences provide an understanding of the conditions for slowing down and intensifying mass transfer processes in the concrete – biofilm – liquid medium system. The engineering methodology of calculation of mass transfer parameters and service life of concrete is applicable at any stage of operation of reinforced concrete products and structures and makes it economically feasible to assign protective equipment and set the terms of their use.
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