EVALUATION OF MOISTURE DIFFUSION COEFFICIENTS IN CEMENT PLASTERS BASED ON DESORPTION PROCESSES

摘要

This paper presents a new approach to evaluation of diffusion coefficients in cement-based materials by testing three kinds of mortars of different water-cement ratio w/c at different moisture levels.Authors decided to divide the entire range of the air relative humidity into five narrow neighboring sections ???intentionally to applied a linear diffusion equation for estimation of the diffusion coefficient in each section.The diffusion coefficient was determined through adjustment of the theoretical and experimental desorption curves using the Levenberg-Marquardt modified iterative algorithm.It has turned out that the obtained in this way diffusion coefficients reveal different values for the individual sections of the air relative humidity,which prove that the diffusion process in the entire range of air relative humidity is highly nonlinear.The value of these coefficient differentiate for different values of the water-cement ratio w/c.