Moisture Transport Properties Research Articles

CloudSat Observations Show Enhanced Moisture Transport Events Increase Snowfall Rate and Frequency Over Antarctic Ice Sheet Basins

AbstractElevated moisture transport over the Antarctic ice sheet can increase snowfall and ice mass. Previous studies used ground‐based observations, reanalysis products, and atmospheric models to evaluate the relationship between extreme moisture transport and snowfall properties. Here, we build on previous studies by combining reanalysis and CloudSat radar snowfall retrievals to examine impacts of extreme moisture intrusions on changes in snowfall frequency and intensity over glacier basins on the Antarctic ice sheet. We examine the impacts of enhanced moisture transport events on snowfall frequency and intensity over two different regions on the Antarctic ice sheet: the Amery Ice Shelf of East Antarctica and the Thwaites and Pine Island glacier basins of West Antarctica. We determine when the median integrated water vapor transport from reanalysis exceeds the 95th percentile within the glacier basins of interest to define enhanced moisture transport events. We then use CloudSat radar snowfall retrievals to evaluate differences between snowfall frequency and intensity during enhanced water vapor transport events compared to the seasonal means for 2007–2010. We find that enhanced moisture transport events over the Amery Ice Shelf and Thwaites and Pine Island glacier basins coincide with higher snowfall frequency and intensity. These enhanced moisture transport events have the potential to alter surface mass balance within glacier basins, with implications for future rates of sea level rise.

A Study on Moisture Transport Properties of Polyester Knit Fabrics for Application in Textile Products

A Study on Moisture Transport Properties of Polyester Knit Fabrics for Application in Textile Products

Moisture transport properties of concrete with SCMs – descriptions, test methods and some applications

AbstractMoisture transport properties of concrete are rarely determined, simply because it is difficult and time‐consuming. Most studies in literature are limited to cement paste and mortar. Translation of these properties to concrete are not straight‐forward. Recently, however, a few measurements are done, also on concretes with supplementary cementitious materials.An overview is given on various ways of theoretically describing the moisture transport properties of concrete, with different “moisture transport coefficients” and their interrelations. Methods of determining those properties are shown and their advantages and drawbacks are discussed. Available data in literature are summarized and compared. A recently developed test method, the tin‐can method, is described. New results are shown for concretes with SCMs. The method's possibilities to be used for short‐term tests of aging concrete are discussed.A few important applications where the moisture transport properties are decisive are presented: applying moisture‐sensitive flooring materials on concrete floor slabs and carbonation‐initiated reinforcement corrosion under varying climatic conditions.

How to design the drying of porous materials?

The convective drying of porous materials is studied at the pore scale using a two-component two-phase Lattice Boltzmann model. Capillary pumping from coarse to fine pores is found to enhance the drying in first drying period at high rate. A ‘toy’ model of four connected channels is developed to design the drying of porous materials. This approach has to be seen to supplement the continuum modelling of drying using known moisture transport properties and convective moisture transfer coefficient, allowing to better understand convective drying and design the pore structure to optimize the drying rate.

Sensitivity Analysis of Traditional Solid Masonry Wall to Frost Damage in North China

The historic façades are significant to building heritage, but they are also extremely vulnerable to changing environmental conditions. Water is well studied as the primary agent that causes the deterioration of porous materials, but the impact of variations in moisture storage, moisture transport, and thermal properties of the materials in solid masonry wall construction remains uncertain and requires quantitative analysis. Sensitivity analysis of solid wall construction can be beneficial in understanding the correlation between material properties and risk in proposing rational preservation strategies. This paper aims to investigate the predominant parameters for frost damage criteria in traditional Chinese masonry construction in North China. Under typical outdoor climate conditions in North China and a constant indoor climate, a 2D Heat, Air Moisture (HAM) model is applied to 240mm and 370 mm thick walls. The sensitivity analysis is quantified with three frost-related criteria. The hygrothermal simulation validates that the main dominant factor varies with different criteria and that the properties of adjacent materials dominate the frost damage risk at certain locations. The results could contribute to the expansion of the international material database and the conservation of masonry heritage from the risk of the freeze-thaw cycle.

Aqueous polyacrylate latex nanodispersions used as consolidation agents to improve mechanical properties of Prague sandstone

This investigation aims at assessing the potential of polyacrylate latex nanodispersions as consolidation agents for sandstones. Four different latex types, implementing polymer fluorination and chemical crosslinking, have been synthesized at the scope and fully characterized. The Prague sandstone employed in this study has been selected as an example of highly porous stones used as building materials for many historical monuments. Two different concentration levels of nanodispersions have been adopted. The consolidated stone samples have been tested using a combination of physical-mechanical tests and microscopic observations. Compared to the non-treated samples, significant increments of mechanical properties (e.g. up to 3.3 times higher bending strength) have been detected after the consolidation treatment with concentrated products. Moreover, when 10 times diluted latex nanodispersions have been applied, the improvement of mechanical properties has still been significant, while moisture transport properties, such as water absorption, have been found to be comparable with those of the untreated sample. Fluorinated polymers imparted better hydrophobic properties with a contact angle above 100°. Observations using a scanning electron microscope revealed the good filling and bridging capacity of the applied consolidation agents. As demonstrated, by acting on the polymer structure, that is, by tuning the degree of crosslinking, polymer fluorination and gel content, the properties of these novel polyacrylate latex nanodispersions can be tailored to the specific stone and type of decay in order to improve the effectiveness of the treatments and obtain the desired final properties. The flexibility of their chemistry offers new opportunities for preserving objects of cultural heritage that are also at risk due to the ongoing climate change.

The Importance of Moisture Transport Properties of Wall Finishings on the Hygrothermal Performance of Masonry Walls for Current and Future Climates

A render is the first protective layer of exterior walls against the outdoor climate, which, due to its constitution, aims to gradually slow down the liquid moisture penetration to prevent it from reaching the wall inner layers. Due to the future expected changes in the outdoor climate, today’s exterior mortar might not be adequately designed to protect these walls. This paper aims to analyse the influence of mortars on the hygrothermal performance of solid brick walls under current and future climates. The study includes four types of assemblies and three types of mortars, and it was carried out for Lisbon and three other climates by using a computational simulation tool. Finally, the moisture gains and respective reach due to the future wind-driven rain (WDR) spells were assessed by means of using future weather files for Lisbon’s climate. It was shown that the solid brick layer is influenced differently depending on the characteristics of the mortar layers and outdoor conditions. In terms of WDR spells, aside from the precipitation and the spell period, the distribution of the WDR events within the spell also conditions the dryness of the assembly. The depth that the outdoor moisture was able to reach varies between 94 and 200 mm.

Evaporation coefficient determination during the capillary rise

Thermo-physiological comfort refers to the heat and moisture transport properties of clothing and how the clothing helps maintain the body's heat balance during various activities. To maintain the thermoregulation of the body, the resulting sweating should be absorbed by wicking fabrics close to the skin and evaporated to the ambient air. In this study, a mathematical model was developed considering evaporation during the capillary rise, based on the geometric configuration of a jersey-knitted fabric and taking evaporation into account. This model was used to calculate the evaporation coefficient. Based on the activities of the worker, sweat diffusion is controlled by capillary diffusion and moisture evaporation. The effect of air velocities of 0 m/s, 1 m/s, and 2 m/s, representing non-walking, walking, and running activities of a worker, respectively, was studied during capillary diffusion. The experiments were conducted at different relative humidities. The results show that the evaporation coefficient depends on the worker’s activities and the relative humidity ratio.

The NMR core analyzing tomograph: a multi-functional tool for non-destructive testing of building materials

NMR is becoming increasingly popular for the investigation of building materials as it is a non-invasive technology that does not require any sample preparation nor causes damage to the material. Depending on the specific application it can offer insights into properties like porosity and spatial saturation degree as well as pore structure. Moreover it enables the determination of moisture transport properties and the (re-)distribution of internal moisture into different reservoirs or chemical phases upon damage and curing. However, as yet most investigations were carried out using devices originally either designed for geophysical applications or the analysis of rather homogeneous small scale (< 10 mL) samples. This paper describes the capabilities of an NMR tomograph, which has been specifically optimized for the investigation of larger, heterogeneous building material samples (diameters of up to 72 mm, length of up to 700 mm) with a high flexibility due to interchangeable coils allowing for a high SNR and short echo times (50–80 μs).

Graffiti removal on external thermal insulation composite systems through chemical-mechanical methods: A feasible protocol?

External thermal insulation composite systems (ETICS) have been widely adopted for improving the thermal comfort of building facades. Although these systems are commonly subjected to vandalism in urban areas, no protocols for the removal of graffiti on ETICS have been yet systematically defined.In this work, aerosol graffiti sprays (blue and silver) were applied on ETICS with different compositions and then removed through chemical (alkaline graffiti removers) and/or mechanical methods (brushing). The moisture transport properties and the aesthetic features of ETICS specimens were characterized prior and after graffiti removal, aiming at assessing the effectiveness and compatibility of the cleaning action.Results show that the effectiveness of graffiti removal strictly depends on the type of aerosol graffiti spray and of ETICS surface. The use of chemical or mechanical methods can lead to severe damage on systems with EPS-based thermal insulation layer and/or silicate or lime-based finishing coats, with an increase of the water absorption and alteration of the chromatic coordinates.

Evaluation of Moisture Transport Properties Based on Modelling of Silane-based Impregnation Agent Effects on Concrete Surface Layer

It is now desirable to establish a technique for long-term prediction of the effects of silane-based impregnation agent on concrete structures exposed to various environments. To meet this requirement, the purpose of this study is set to establish the model to evaluate the effect of a silane-based impregnation agent on the waterproofing properties of cementitious materials based on microscopic mechanisms. Several mortar specimens were prepared with the silane-based impregnation agent, and moisture absorption and evaporation experiments were conducted. The results showed that the application of the agent was shown to effectively inhibit the penetration of moisture into the interior of the cementitious materials. The effect of the silane-based impregnation agent was modeled in a multiscale pore structure model by applying a microscopic water-repellent effect to the pores in which no pore water was present at the time of agent coating. The analysis with proposed model showed that, as in the experiment, the moisture supply was reduced by the application of the agent, whereas the amount of moisture loss remained almost the same with and without the agent. Moreover, the analysis quantitatively showed that the water content can continue to decrease with silane treatments, even under repeated wet-dry conditions.

Moisture and ion transport properties in blended pastes and their relation to the refined pore structure

This paper presents a study of the moisture transport properties in blended pastes measured by a new procedure and setup. The dependence of moisture transport coefficient on relative humidity (RH) is confirmed. The differences in the moisture dependency may be due to discrepancies in the critical RH for the percolation of liquid. Fly ash and slag increase the percentage of mesopores or “ink-bottle” pores with a mesoscale neck and they strongly reduce the pore connectivity in pastes. These effects cause the evident reduction in the moisture and chloride diffusivity. The additional replacement with limestone filler has little effect on the pore connectivity. The formation factor controls the moisture transport at the high RH interval, but the volume of small pores (middle capillary and mesopores) is the major determinant at a low RH interval. The relationship between water-binder ratio, pore structure and moisture transport or chloride migration coefficient is discussed.

Development of a novel fluorocarbon coated acquisition-barrier fabric layer for incontinence application

Development and characterization of single-faced spun lace polyester-viscose (30:70) fabric as a top layer in incontinence products have been reported. One side of the fabric layer is coated with fluorocarbon using the spray coating process to make it hydrophobic. The coating process parameters, spraying distance (distance between spraying nozzle and fabric), finish concentration, and the partial coating are varied to determine the optimum combination. The effectiveness of the coating process has been assessed by measuring contact angle, moisture management, and rewet tests. The study reveals that the 30 cm spray distance and 5% finish concentration, sprayed following dot/zebra pattern, provides the layer's best liquid moisture transport properties. This process of making the front side hydrophobic and the other side hydrophilic promotes one-way liquid transport and can be very useful for many absorbent medical and hygiene products.

Development of biodegradable tri-blended fabrics with improved moisture management properties using cotton/polylactic-acid/bamboo-viscose fibres

The influence of fibre blend composition on the moisture management properties of tri-blended cotton-rich knit fabrics with biodegradability has been studied. The cotton, polylactic acid and bamboo-viscose fibres are blended to produce yarns of 14.7 tex (40s Ne) with four different blend proportions, namely 60/20/20, 50/30/20, 50/20/30 and 40/30/30. The yarns are then knitted into a single jersey structure of 130-135 gsm, followed by its scouring, bleaching and relaxation treatments. The relaxed fabrics are then evaluated for dynamic moisture transport properties using the SDL Atlas moisture management tester. The moisture management test results indicate that blending polylactic acid fibres with cotton and bamboo-viscose fibres improves the blended fabric's moisture management properties. The overall moisture management capability value is found to be better for cotton/polylactic-acid/bamboo-viscose blended fabric in the proportion of 50/30/20.

Biodegradable trilayered micro/nano-fibrous membranes with efficient filtration, directional moisture transport and antibacterial properties

Particulate matters (PMs) pollution and bacteria severely affect human health. Fibrous filters have shown great potential in intercepting PMs and bacteria. However, developing a novel respirator material endowed with multi-functions, such as efficient filtration, antibacterial activity, directional moisture transport and biodegradability is still challenging. Herein, a multifunctional air filtration membrane with hierarchical structure was fabricated by sequentially electrospinning poly (ε-caprolactone) (PCL) fibrous membrane, PCL/gelatin fibrous membrane and PCL/gelatin/ε-poly (L-lysine) (ε-PL) fibrous membrane. The fabricated trilayered fibrous membrane exhibited high PM filtration efficiency and a low pressure drop. Moreover, the fibrous membrane possessed excellent antibacterial activity due to the incorporation of ε-PL. In addition, the trilayered fibrous membrane provided directional water transport performance by the combination of hydrophobic fibrous layer and hydrophilic fibrous layer, thus improving the comfort of the wearer. Importantly, benefiting from the biodegradability property of PCL, gelatin and ε-PL, the fibrous membrane was biodegradable, which could decrease the burden on the environment. The fabricated trilayered fibrous membrane not only shows promising potential as a highly efficient, antibacterial, moisture-wicking and biodegradable air filtration membrane, but also offers a versatile strategy to design a multifunctional face mask.

Comfort properties of fabrics knitted from a two-ply yarn derived from abacá and cotton

In the present study, the comfort properties of knitted fabrics made from a two-ply yarn comprising a paper yarn and a cotton yarn were investigated. The objective was to elucidate the characteristics of paper yarn in comparison with cotton in terms of the design and development of comfortable and ecofriendly textiles that directly contact the skin. A two-ply yarn comprising a paper yarn made from abacá and a cotton yarn was prepared. Five fabrics with different proportions of paper were prepared by changing the knitting ratio of the two-ply yarn to a 100% cotton yarn. The mechanical properties (tensile, shearing, bending, compression, surface, contact area, and air permeability properties) and various thermal and moisture-transport properties of the fabric samples were determined. Those investigations revealed that the surface roughness increased, the friction coefficient decreased, the contact area decreased (in both the dry and wet state), the air permeability increased, the thermal conductivity increased, and the moisture diffusivity increased as the proportion of paper yarn increased. The fabric consisting of only the two-ply yarn was noticeably stiffer than the fabrics that also contained a pure cotton yarn. The results suggest the possibility of developing clothes that feel comfortable next to the skin, even when wet (e.g. underwear and socks) by knitting the two-ply yarn in a well-balanced ratio with cotton yarns.

Analysis of thermal and wet comfort properties of hygroscopic and exothermic knitted fabrics

Clothing thermal and wet comfort relates to the heat and moisture transport properties of clothing as one of the most important factors in determining whether or not a garment is desirable to customers. It is important to develop winter textiles by optimally combined technology of hygroscopic heat generation and moisture management to maintain warm dry skin for the active wearer. In this work, six multilayer hygroscopic and exothermic fabrics made up of different functional yarn compositions were designed and fabricated based on ergonomic principles. Their thermal wet comfort properties were investigated compared with seven plain knitted fabrics. Air permeability, moisture management characteristics, thermal physiological properties, and hygroscopic heat generation performances were used to assess thermal and wet comfort properties. Their correlations with yarn composition were explored. Multilayer knitted fabrics with a designed knitted structure and wettability gradient demonstrated evenly hygroscopic exothermic properties and excellent directional moisture transport performances. This has the potential to reduce the phenomena of high temperature and heat concentration following moisture absorption The fabric made up of profiled polyester and a low proportion of cotton blend as an inner layer and a high proportion of modified polyacrylate and viscose blend as a middle layer was verified to have superior moisture management characteristics and evenly hygroscopic exothermic properties.

Rheological and mass transport characteristics of hydrocolloid incorporated multilayered wheat flour dough sheet (Khaja) during frying

The purpose of this study was to analyze the effect of the addition of hydrocolloids such as gum arabic and xanthan gum, as well as a mixture of gum arabic and xanthan gum on moisture and oil transport properties in deep fat-fried multilayered wheat flour dough sheet (Khaja). The dynamic viscoelastic analysis of the dough showed that the hydrocolloid incorporated sample had a larger difference in the storage and loss modulus values, indicating that hydrocolloids had a synergistic effect on increasing the elastic property of the dough. The multilayered wheat flour dough sheet was deep fat-fried in a fryer at a frying oil temperature of 180°C. Hydrocolloid inclusion reduced the moisture diffusivity of the product, and the moisture diffusivity of the hydrocolloid incorporated sample decreased from 4.60 × 10−9 to 3.32 × 10−9 m2/s. The sample containing the combination of gum arabic and xanthan gum reduces oil absorption by 20.13% compared to the control sample. Novelty impact statement Oil absorption in Khaja is influenced by the type of hydrocolloid, moisture content of the dough, frying duration, and temperature of frying. Hydrocolloid significantly affected the viscoelastic characteristics of the dough and reduced the hardness of the product. The dough containing a combination of xanthan gum and gum Arabic decreased oil absorption by around 20% in Khaja.

Aperture and permeability of aged concrete joints

Often concrete structures cannot be regarded as monolithic since discontinuities like cracks and joints develop inevitably during construction and service life. Joints are not only introduced coincidentally at interfaces of different concreting steps, they are also induced deliberately to release stresses due to thermal actions or shrinkage in a controlled manner. This results in a change of material properties at the joint and is often investigated from a mechanical point of view. However, joints are also changing locally the moisture transport properties of a structure and thus considerably affecting the durability of those. Given the lack of data in the literature, in the presented work the distribution of the joint aperture and hydraulic conductivity is measured for a set of aged concrete expansion and cold joints. It is shown that the distribution of the apertures can be modeled with common probability distribution functions, which allow a relation between saturation and capillary potential. The parallel plate model is found to be a good estimate for the hydraulic conductivity of the joints when the available void areas of the joint are considered.

Modeling and estimation of moisture transport properties of drying of potential Amazon biomass for renewable energy: Application of the two-compartment approach and diffusive models with constant or moisture-dependent coefficient

Mathematical modeling and estimation of moisture transport properties in drying of acai biomass were done in this work. The first approach consisted of applying the diffusive model for three different boundary conditions at the particle's surface and the effective diffusivity considered a constant or variable parameter. It was found that the model's accuracy depended on the drying level and the boundary conditions for the effective diffusivity assumed as a constant parameter. Accordingly, the results from the Arrhenius relationship depended on the predictions of the different approaches of the diffusive model, giving different values of the activation energy for the same experimental condition. The effective diffusivity ranged from 9 × 10−11 to 7 × 10−10 m2 s−1 and the activation energy from 38 to 55 kJ mol−1, indicating a high resistance to moisture evaporation. The predictions were not improved when considering the effective diffusivity as a moisture-dependent parameter, possibly due to the simplifications used for calculations. The two-compartment concept consisted of a set of differential equations that gave the best concordance with experimental data. The kinetics parameters ranged from 0.2 to 17 h−1 and presented a well-defined variation with the operating conditions, encouraging its use in drying optimization for efficient conversion processes.