A double-porosity model for water flow in unsaturated concrete

Abstract

This paper presents a double-porosity model for describing the moisture flow in unsaturated concrete. The two porosities used in the model represent the small pores of nanoscale and large pores of micro-scale, both of which are partially saturated with the moisture transport described by Darcy's law but with different transport properties. The model is applied to investigate the internal variation of saturation in a concrete in response to the change of humidity in the environment where the concrete is exposed. It is found that during wetting and drying cycles, the desaturation zone in concrete created in the first cycle expands continuously during the subsequent drying-wetting cycles. The wetting and drying cycles can push the desaturation zone from the surface layer into inner concrete gradually. This feature has not been explored in existing transport models.

Two‐scale continuum model for simulation of acid fracturing in carbonate reservoirs with two main mineral components

“…However, dolomite dissolution is associated with fewer wormholes (Figure 7E)-there is indeed the tendency to create multiple wormholes during the uneven acid etching of the fracture surface, and yet once the growth tendency of one wormhole is improved, the other wormholes stop developing. 43,44 For the dolomitic limestone (Figure 7B), the dissolution morphology is similar to that in the pure limestone. Meanwhile, the dissolution morphology of the limy dolomite (Figure 7D) is analogous to that of the pure dolomite.…”

“…Calcite dissolution tends to create numerous acid‐etched wormholes (Figure 7A), ending up with multiple high‐conductivity channels. However, dolomite dissolution is associated with fewer wormholes (Figure 7E)—there is indeed the tendency to create multiple wormholes during the uneven acid etching of the fracture surface, and yet once the growth tendency of one wormhole is improved, the other wormholes stop developing 43,44 . For the dolomitic limestone (Figure 7B), the dissolution morphology is similar to that in the pure limestone.…”

Modelling hydraulic and capillary‐driven two‐phase fluid flow in unsaturated concretes at the meso‐scale with a unique coupled DEM‐CFD technique

“…When the porosity is less than about 20%, huge numerical problems arise. 32 When compared to other existing models in the literature, 27,[33][34][35][36] the authors' numerical mesoscopic coupled DEM/CFD approach for modelling hydraulic-and capillary-driven fluid flow in unsaturated concrete (porous material of very low porosity, lower than 15%) at the meso-scale subjected to external load has an innovative element: detailed tracking of water/gas fractions in pores regarding their varying geometry, size, and location. There are no coupled hydro-mechanical DEM/CFD multi-phase fluid flow models available in the literature that might be used to simulate capillary-driven multiphase flow in unsaturated concrete subjected to external loads.…”

The characterization of chloride effect on concrete water sorption and its application in the modelling of concrete conditions in tidal zones

“…Type 2 explicitly describes the coupled pore water convection and chloride diffusion mechanisms using a water infiltration model together with Fick's law [15]. The environmental and the material factors, which link to the two transport mechanisms, can be specified in the modelling [16] (for example, the influence of cylic wetting and drying conditions [17][18][19], the effect of the electrical double layer at the pore surfaces [20], the osmotic effect [21], and the effect of double-porosity in concrete [22]).…”