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Hygric pore network modelling, which characterises the macroscopic moisture storage and transport properties by simulating the microscopic storage and transport of moisture in the pore elements of the pore network, is a novel method to characterise the hygric properties of building materials. To analyse, verify and/or compare pore networks, a wide array of parameters (both geometrical and topological) exists. This paper aims to comprehensively investigate these parameters, targeting their impacts on the moisture retention and permeability curves of porous materials. The maximum-inscribed-ball method is employed to extract the pore networks of three real porous materials, which are further scaled down to provide three complementary virtual pore networks in order to cover a wider spectrum of pore sizes. Subsequently, these pore networks are modified to obtain variations in the parameter distributions, and then, a sensitivity analysis is implemented to determine the impact of the pore network parameters on the hygric property prediction. The results indicate that the moisture retention curve is most related to the radius and volume distributions of pore bodies and throats, whilst the distribution of coordination number is the most crucial parameter for the moisture permeability curve. The conclusions are further confirmed through an improved stochastic pore network generation algorithm. With preserved radius and volume distributions for pore bodies and pore throats, the moisture retention curve is predicted accurately. Adding information on the coordination number distribution to the algorithm then ensures the successful prediction of the moisture permeability curve. Article Highlights: Key pore network parameters governing the moisture transfer are determined, valid in both micro- and nano-scale. An improved stochastic pore network generation algorithm is proposed. Surface adsorption and surface flow are crucial in nanometre region. [ABSTRACT FROM AUTHOR]

With the development of more efficient hygrothermal computer models, simulation studies have become increasingly important in the design of building components. To obtain trustworthy results from these studies, accurate hygric properties are required. The existing methods for moisture storage properties, however, are not very well suited to accurately measure moisture retention curves within a compact timeframe. To improve on this front, this paper introduces the steady state centrifuge technique, a common experiment in soil physics, for use on porous building materials. The laboratory centrifuge, used for the validation of this technique, is self-made to limit its cost and account for specific design choices. In the first part of the paper, the design of the laboratory centrifuge is described and all problems encountered during the development are explained and resolved. The two main problems are excessive heat generation by the motor and unwanted evaporation from the sample's surfaces. The excessive heat generation is solved by extraction of heat both at the source, by using a ventilator, and at the rotor, by adding carefully positioned air extraction holes. The unwanted evaporation is eliminated by incorporating sample holders to shield the sample from the surrounding air. In the second part of the paper, the steady state centrifuge experiment is used to measure the desorption moisture retention curves of a ceramic brick starting from both saturated and capillary moisture content. The results are validated by their similarity to the curves obtained by mercury intrusion porosimetry. Besides providing accurate results, the determination of the full moisture retention curve requires only 1–2 weeks, which is significantly quicker than other common protocols, such as the pressure plates, which take about 2 months. Additionally, the ability to measure the desorption moisture retention curve from capillary moisture content as well as the limited cost of the centrifuge design (€6000) provide major advantages. [ABSTRACT FROM AUTHOR]

A reliable and practical method of hygric property characterisation is a major determinant in properly analysing hygric performance of built constructions. The current empirical approach, however, yields data that are still incomplete, not fully representative, and not entirely reliable. In this study, hygric properties are therefore determined directly from pore structure information by applying stationary unsaturated pore-scale physics to model moisture storage and transport. The pore space is captured by visualisation techniques and further extracted into a discrete network of variably shaped pore bodies interconnected by pore throats. In this network, corner and surface adsorption and capillary condensation are simulated to define the moisture storage. Air entrapment is furthermore considered to determine the capillary moisture content. The resulting spatial moisture distribution in the pore network allows moisture to flow, in wet elements in the liquid phase and in dry elements in the vapour phase. The adsorbed corner and surface films moreover enable additional liquid flow. These various simultaneous flows aggregately define the transport property. A comparison to measured data validates the presented hygric property model. [ABSTRACT FROM AUTHOR]

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In this work an attempt is made to compare experimental soil moisture profiles for a horizontal infiltration experiment (Poulovassilis, Water Resour Res 13:369-374, ) with calculated profiles. These calculated profiles are obtained variously through the use of the computation code of HYDRUS 1D and through the semi-analytical solution of the appropriate diffusion equation when the soil water diffusivity is obtained directly from the experimental data. The necessary input data for using HYDRUS 1D are obtained in three different ways: First, the experimental data of the main wetting branch of the moisture retention curve (MRC) coupled with Ks (the hydraulic conductivity at saturation) are used. Second the predicted, according to the Parlange model (Parlange, Water Resour Res 12:224-228, ) main wetting branch of the MRC, when experimental data points of the main drying branch of the MRC are used. Third the predicted, according to the Mualem model (Mualem, Water Resour Res 13:773-780, ) main wetting branch of the MRC, again when experimental data points of the main drying branch of the MRC, are used. In the previous three cases predicting appropriate hydraulic conductivity K( θ) relationship is obtained through the model of Mualem (Water Resour Res 12:513-522, ). The comparison of the above soil moisture profiles leads to the following: The numerically calculated profiles are moving faster than the experimental ones. Calculated profiles exhibit a Green-Ampt-like shape. Differences among the experimental and calculated profiles are more pronounced in larger θ-values. Closer to the experimental profiles are those obtained semi-analytically. From the cumulative infiltration versus square-root of time curves, it is evident that the HYDRUS 1D results are compatible with the requirements imposed by the Boltzmann transformation. [ABSTRACT FROM AUTHOR]

Abstract: Direct determination of soil hydraulic properties is often costly and laborious hence the use of indirect methods such as pedotransfer functions (PTFs). Despite progress made in PTF development in general, little evaluation of PTFs has been done for the sandy soils of Niger. We tested the ability of three PTFs, (Campbell, van Genuchten, and Vauclin) to determine soil water retention and unsaturated hydraulic conductivity (K) for sandy soils at two villages (Banizoumbou and Bagoua) in Niger. Modeled K was compared to K estimated from neutron probe readings at 1.4 m; and modeled moisture retention was compared to lab measurements derived from the hanging water column method and pressure plate apparatus for the following depth intervals: 0–30, 30–60, and >60 cm at Banizoumbou; and 0–30, 30–120, and >120 cm at Bagoua. The Campbell PTF resulted in lower root mean square error (RMSE) (0.05–0.06 m3 m− 3) for soil moisture retention for the three depth intervals at the two sites and performed better than the van Genuchten function (RMSE 0.06–0.07 m3 m− 3) for Bagoua soils which had higher sand content. The van Genuchten PTF consistently overestimated dry regime moisture retention for the three depth intervals especially at Bagoua but performed well for the wet regime. The Campbell and Vauclin PTFs underestimated K (RMSE 0.61–1.01 mm d− 1) at both sites whereas the van Genuchten model was close to field measurements (RMSE 0.26–0.47 mm d− 1). These results show that the Campbell model is a cheaper alternative to direct measurement of moisture retention and the van Genuchten function can be used to estimate K for Niger''s sandy soils with modest accuracy. [Copyright &y& Elsevier]

Four successive trials with gypsophila, rose, cucumber, and lettuce grown on different pumice grades were conducted in a heated glasshouse. In the gypsophila experiment, three grades of pumice (0 to 2, 0 to 5, and 0 to 8 mm) were tested, whereas in the rose, cucumber, and lettuce experiments, four pumice grades (0 to 2, 0 to 5, 0 to 8, and 4 to 8 mm) were compared. In each experiment, these pumice grades were combined with two growing systems, specifically placement of the same media volume either in pots or in bags. Furthermore, the physical properties of the tested pumice grades were determined. Overall, gypsophila and cucumber gave the highest yields when grown in pots filled with the two finest pumice grades, whereas the yield obtained from plants grown in bags was poor regardless of particle size range. Coarse pumice restricted gypsophyla and cucumber yield in pot culture to nearly the same degree as in bags. In contrast, lettuce, and to a greater degree roses, exhibited a weaker response to the different pumice grades and growing systems. The two finer pumice grades were characterized by relatively low air-filled porosity, which presumably restricted plant growth and yield as a result of poor root aeration when the media were placed in bags with a height of 8 cm. The coarsest pumice grades were characterized by a steep drop in the water content as the suction increased only a few centimeters above zero, which imposed an appreciable lowering of the overall water content in the pots in comparison with the bags (≈12.5%), as a result of the increased height of the former. Our results indicate that gypsophila and cucumber respond more strongly than roses and lettuce to the variations in the air-to-water ratio in the root zone originating from differences in the physical properties of the growing media. [ABSTRACT FROM AUTHOR]

The moisture storage parameters of three different building materials: calcium silicate, ceramic brick and autoclaved aerated concrete, are determined in the hygroscopic range and overhygroscopic range. Measured sorption isotherms and moisture retention curves are then combined into moisture storage functions using the Kelvin equation. A comparison of measured results with global characteristics of the pore space obtained by mercury intrusion porosimetry shows a reasonable agreement; the median pore radii by volume are well within the interval given by the beginning and the end of the characteristic steep parts of the moisture retention curves.

Water resources can be used more efficiently by including sustainable substrate components like coir that increase water-holding capacity. The first objective of this study was to evaluate the impact of coir amendment rate on plant available water and plant gas exchange, with the goal of optimizing substrate available water and determining the optimum coir amendment rate in a greenhouse environment. The second objective was to establish the optimum method of determining plant available water using either plant gas exchange parameters or substrate physical properties. Greenhouse experiments were conducted with Hydrangea paniculata 'Jane' (Little Lime® hardy hydrangea) potted with one of five different coir rates (0%, 10%, 25%, 40% and 65%) mixed with pine bark on a volume basis. Plant gas exchange parameters and substrate water content were measured daily over a range of increasingly drier substrate moisture contents. Actual photosynthetic rates increased with increasing coir amendment rate and were highest with 65% coir amendment. Amending pine bark with coir increased the water storage capacity, plant available water, and plant gas exchange parameters. Results suggest that 65% coir amendment rate was the optimum amendment rate among those tested in a greenhouse environment and plant photosynthetic rate was the better method of determining plant available water. [ABSTRACT FROM AUTHOR]