A non-stationary problem of moisture transport in a diaphragm wall with account taken of filter cake

Abstract

Introduction. The analysis of moisture fields in a diaphragm wall is needed to determine such rheological parameters of concrete as creep and shrinkage deformations. Materials and methods. In the paper, the main solution was obtained by expansion into the trigonometric Fourier series using data on diffusion properties of materials identified by reviewing the studies. Results. By solving the problem of moisture transport in the diaphragm wall, taking into account filter cake, the authors found out that the relative humidity in the concrete pore space decreases extremely slowly over time. Linear distribution is achieved only 48 years after the excavation of the diaphragm wall. At a depth of 20 cm, humidity dropped to 92 % on day 365 and to 82 % after 3 years. In the 6th year, the drying of concrete by the atmospheric air affects the boundary with filter cake and continues until the 48th year, when the relative humidity of concrete takes a steady value of 69 %. Conclusions. The analysis of the accurate solution shows a strong effect of filter cake on the drying rate of the diaphragm wall. Low diffusion permeability of filter cake accelerates the drying of concrete. Given that the coefficient of diffusion of filter cake is 15.6 ∙ 10–8 m2/day, its effect manifests itself in deep layers after 3 years. Relative humidity of air in a trench is more significant for near-surface areas.