Mass Transfer Phenomena in the System «Cement Mortar- Fiberglass Reinforcement» at the Stage of Composite Structure Formation Part 1. Physical Representations and Mathematical Formulation of the Problem

Abstract

The article describes the phenomena of moisture transfer in the system «fiberglass reinforcement - cement mortar» at the stage of hardening and structure formation of the composite. To obtain a mathematical model of moisture transfer in the formation of the cement matrix, the equations of mathematical physics, the equations of unsteady mass transfer and the differential equations of mass conductivity of parabolic type are used. The influence on the moisture transfer processes in the system «fiberglass reinforcement - cement mortar» of the conditions of hardening of the composite is considered: at the absence of external mass transfer; at the evaporation of moisture from the surface, when the fiber does not absorb water from the cement mixture, and with simultaneous evaporation of moisture from the surface and the absorption of water by the fiber. The obtained physical and mathematical model of moisture transfer for the system «cement mortar - fiberglass reinforcement» allows to take into account the change in water-cement ratio at the stage of hardening of the composite and to establish its influence on the structure formation of the composite, on the processes of self-compaction of concrete, its deformative and operational characteristics, as well as on the structural and phase composition of concrete. Mathematical models make it possible to establish the required water-cement ratio for obtaining a composite with specified characteristics, such as compressive strength and tensile strength, crack resistance, density, porosity, corrosion resistance. The formulated physical and mathematical problem can be solved for particular cases by the method of microprocesses, which will allow to calculate the strength characteristics of the composite and to carry out a numerical analysis of the durability and reliability of products and structures of concrete witha composite reinforcement.