Thermo‐hydro‐mechanical analysis of partially saturated porous materials

Abstract

Presents a fully coupled numerical model to simulate the slow transient phenomena involving heat and mass transfer in deforming partially saturated porous materials. Makes use of the modified effective stress concept together with the capillary pressure relationship. Examines phase changes (evaporation‐condensation(, heat transfer through conduction and convection, as well as latent heat transfer. The governing equations in terms of gas pressure, capillary pressure, temperature and displacements are coupled non‐linear differential equations and are discretized by the finite element method in space and by finite differences in the time domain. The model is further validated with respect to a documented experiment on partially saturated soil behaviour, and the effects of two‐phase flow, as compared to the one‐phase flow solution, are analysed. Two other examples involving drying of a concrete wall and thermoelastic consolidation of partially saturated clay demonstrate the importance of proper physical modelling and of appropriate choice of the boundary conditions.

Combined heat and mass transfer for drying ceramic (shell) body

“…Towards the end of the drying period, the gas pressure decreases, tending back to the ambient condition. A similar evolution in gas pressure during convective drying has been presented in several other works, such as in brick drying [9], in consolidating a slab of porous material [25], in drying of a concrete wall [26] and in drying of light concrete [27].…”

Behaviour of cement concrete at high temperature

“…The spalling of concrete is one of the more interesting phenomenon occurring in conditions of fire. The literature broadly describes it, both from the experimental [17,[24][25][26] and the theoretical side, on the bases of various mathematical models of this effect [27,28]. The main factors causing spalling of concrete include: reduced cement matrix porosity and the use of pozzolana additives [29,30], water content in material [29,30] and condition of stresses brought about by the presence of mechanical load and gradient of temperature.…”

Experimental and numerical investigation of sodium sulphate crystallization in porous materials

“…They assume the equilibrium between the precipitated and dissolved salt, therefore they could not be used to calculate the solution supersaturation and the additional stress which was released during salt crystallization. The proposed mathematical model is the extension of the formulation developed by Lewis and Schrefler [13] and then modified by Gawin and Schrefler [14], describing heat and moisture transport in porous building materials, with salt transport and its influence on thermal and hygral processes. A porous material consists of the following phases: solid skeleton, liquid water (salt solution), water vapour plus dry air and precipitated (crystallized) salt.…”