Indirect assessment of hydraulic diffusivity and permeability for unsaturated cement-based material from sorptivity

Abstract

International audienceThe hydraulic diffusivity, water permeability and relative gas permeability for cement-based materials are indirectly evaluated from measured sorptivity and water vapor sorption isotherms (WVSIs). The dependence of sorptivity on initial saturation degree is first established to help calculate hydraulic diffusivity and other transport properties. An experimental program with a self-scaled preconditioning strategy is also carefully designed and conducted on three concretes to measure their sorptivity, WVSIs as well as permeability to various fluids. It's found that hydraulic diffusivity of ambiguous physical significance may be not a good durability indicator. The predicted water permeability is larger than measured value but at the same order of magnitude. This overestimation is attributed to the required drying preconditioning. The predicted relative water permeability agrees well with reported data. However, the predicted relative gas permeability agrees with the measured data from classical CEMBUREAU method better than that from tri-axial permeameter with higher inlet gas pressure

Determination of water permeability for a moisture transport model with minimized batch effect

“…That is why in some papers K l is named as "intrinsic" permeability (e.g., [2,7,8]). Nevertheless, "intrinsic" permeabilities measured by gases (oxygen and nitrogen [9]) and solvents (methanol [10] and isopropanol [11,12]) are often found to be greater than K l . Reasons for this will be discussed later.…”

“…The permeability can be determined either directly by experiments or indirectly by theoretical models based on other measured data. Conventional methods to measure K l are classified as flow-through techniques as they measure the flux under steady state condition for fully saturated specimens, with the geometry of either truncated cones [13] or cylinders/disks [14,15,16,17,18,19,12]. During measurements, the side of the specimen must be sealed and liquid water is injected from one face by applying extra pressure so that the outflow can be only observed on the opposite face.…”

“…Other methods based on theoretical models are also reported in the literature. For instance, a practical method is to use measured sorptivity to assess K l [12] because sorptivity measurements are much easier to perform than the above-mentioned permeability measurements. The first author of this paper introduced two methods to indirectly determine water permeability [8].…”

Relating unsaturated electrical and hydraulic conductivity of cement-based materials

“…These properties are commonly the sorptivity S, saturated hydraulic conductivity K s , open porosity θ s , electrophorosis-related properties (rapid chloride penetration, RCP), and the desorption/adsorption isotherm (Υ d/a (Θ), where 0 ≤ Θ < 1.0 is the degree of saturation). While these parameters are related to unsaturated transport, none completely paints the picture of unsaturated transport in cement-based materials (Zhou et al 2016;Scherer 2015). A more descriptive unsaturated transport property is the unsaturated hydraulic conductivity K. However, obtaining K for cement-based materials using experimental methods is extremely difficult due to the large pressure requirements at low saturation due to the fine pore-size distribution.…”

Pore-scale modelling of relative permeability of cementitious materials using X-ray computed microtomography images

“…Based on a series of experimental results, Monlouis-Bonnaire et al [6] and Wardeh and Perrin [7] proposed a modified Van Genuchten model, which was subsequently validated by Baroghel-Boundy [11]. Recently, some general analytical models for fluid permeability of cementitious materials against degree of saturation were derived from conductivity theory and proposed by Zhou [12] and Zhou et al [13,14]. It is worth mentioning that most of these analytical models are semi-empirical expressions by fitting the limited experimental data.…”