Water Migration Mechanism Research Articles

Water migration mechanism during internal curing of cement composites with cellulose microfibers

This study aimed to investigate the internal curing mechanism of cement composites containing cellulose microfibers (CMFs) derived from kenaf stalk bast. The primary test variable was the CMF content, which controlled the amount of water absorbed by the CMFs, thereby facilitating internal curing. The evolution of proton signals from time-domain nuclear magnetic resonance (NMR) was analyzed for the solid phases and various mobile water components during the curing process. The NMR results showed strong correlation with the thermal decomposition and degree of hydration, as determined by thermogravimetry and quantitative X-ray diffraction, respectively. The higher CMF content led to a delayed onset of hydration at early age. Moreover, the internal curing process was supported by the delay in the detection time of the solid-phase signal and an increase in signal intensities of the interlayer water and solid components, indicating the formation of hydrated phases. These insights clarify the significant role of CMFs in enhancing internal curing effects in cement composites.

Elucidating the molecular mechanism of water migration in myosin gels of Nemipterus virgatus during low pressure coupled with heat treatment

The relationship between myosin denaturation, aggregation and water migration in Nemipterus virgatus myosin gels with different treatment processes under optimal low pressure coupled with heat treatment was investigated to clarify the molecular mechanism of water migration. With the different treatment processes, the proportion of bound water of the myosin gels increased significantly (P < 0.05). Denaturation of myosin S1 sub-fragments and α-helical unfolding during different treatment processes led to an increase in β-sheets content. These promote increased exposure of Try residues and hydrophobic groups of myosin, formation of clathrate hydrates, and reduced mobility of bound water. Furthermore, hydrophobic interactions and disulfide bonds caused the head-head and head-hinge to coalesce into a 3D honeycomb network with greater fractal dimension, less lacunarity, smaller water hole diameter and more water holes. This increased the capillary pressure experienced by the bound water, causing immobile water to migrate towards the bound water. The present study may be necessary to improve the mechanism of water migration in protein gel systems and to promote the industrial application of high pressure processing technology in surimi-based foods.

Electrical resistivity analysis for the internal capillary water migration mechanism of porous stone

Electrical resistivity analysis for the internal capillary water migration mechanism of porous stone

Effect of natural zeolite on water distribution and migration in low water/binder cement-based composites (LW/B-CC) mixed with seawater: An experimental and computational investigation

This study focus on dynamic characteristics of water distribution and migration in low water/binder cement-based composites (LW/B-CC) mixed with seawater and natural zeolite based on experimental and numerical approaches. More exactly, micro/macro properties of LW/B-CC are investigated by experiments and then the mechanism of water migration is analyzed by molecular dynamics methodology. The results reveal that the internal curing effects reflected by 1H nuclear magnetic resonance (NMR) and shrinkage test indicate that porous zeolite alleviates the self-desiccation of LW/B-CC matrix, especially in seawater-mixed LW/B-CC. Besides, the use of seawater improves the interfacial transition zone (ITZ) between zeolite and matrix. Molecular dynamics simulations exhibit an enriched ion content at the zeolite-water interface, which tends to block the transportation of water molecules. Meanwhile, the migration of water molecules is more efficient in Na-heulandite induced by a more equal distribution of extra-framework charges. With evidence from experimental and numerical approaches, ions in seawater are confined by the lattice of zeolite, and more water can be stored in the pores of zeolite and used as internal curing water; hence, zeolite is an appropriate type of aggregate for producing LW/B-CC incorporating seawater.

Investigation of Water and Soil Migration and Mud Pumping of Subgrades under Traffic Load

Atmospheric precipitation leads to the increase of moisture in the subgrade. The moisture and soil migration in subgrade is a key scientific problem in evaluating the service performance of the subgrade and resolving or preventing mud pumping. Using a self-developed testing system as well as a numerical simulation model, a detailed study of the dynamic hydraulic characteristics, water migration mechanism, fine soil migration mechanism, and mud pumping properties of the subgrade was conducted. The results showed that water migrated into the upper layer of the subgrade under traffic load. Meanwhile, a pressure gradient for the pore water was generated in the subgrade. This kind of pressure gradient is beneficial for the moisture and fine soil migration. With rising groundwater level and increasing traffic load, the porosity of the subgrade soil differs at different depths. The fine soil migration is caused by water migration, which causes new migration channel for water in the subgrade. Then, a circulating system of moisture and fine soil is formed in the subgrade under a traffic load. After that, the upper layer subgrade soil is nearly saturated under the action of traffic load. Then, the nearly saturated soil liquefies instantaneously, becoming mud, under the action of traffic load. However, as the loading time progresses, the moisture and fine soil in the subgrade continue to migrate upward, resulting in the mud being pumped into the ballast and the gradual disappearance of liquefied soils at different depths.

Effect of freeze–thaw process on heat transfer and water migration between soil water and groundwater

Understanding the mechanisms of water migration and heat transfer in frozen soil is essential for the selection of water resource management measures and determination of irrigation schemes for winters. However, the dynamics of the groundwater level and temperature caused by freezing and thawing and their impact on soil water redistribution remain unclear. In this field study, the mechanisms of water migration and heat transfer in the soil during the freeze–thaw period under the combined action of the surface temperature change (upper boundary) and groundwater level fluctuation (lower boundary) were comprehensively considered with the theory and method of heat transfer, freeze–thaw characteristic curves of soil, and water balance model. The results showed that: (1) The soil temperature distribution and groundwater temperature dynamics can be interpreted intuitively by the soil temperature gradient and accumulated heat storage. (2) The freeze–thaw characteristic curves of soil indicated that the soil temperature dynamics caused a phase transition of the soil water. This further changed the soil water potential and permeability by 1–2 magnitudes and 1–5 magnitudes, respectively, which affected the direction and quantity of water migration. (3) The water balance quantitatively revealed the controlling effect of groundwater level changes caused by freezing and thawing on soil moisture dynamics. About 20% of the ice in the frozen layer was formed by the upward recharge of the groundwater during the freezing period. In the thawing period, most of this water returned to the groundwater (84%), while the rest (16%) increased the soil water content. These results systematically explain the mechanisms of heat transfer and water migration between the soil water and the groundwater during the freeze–thaw period, providing a theoretical reference for agricultural water management in seasonally frozen regions.

Experimental investigation on mechanical properties and failure mechanism of rock-like specimens containing an arc-shaped ice-filled flaw under uniaxial compression

The study of rock mass properties under low-temperature conditions is an important basis to ensure the stability of engineering in alpine regions and the safety of engineering construction using low-temperature technology. In order to investigate mechanical properties and failure mechanism of water-saturated fractured rocks at low temperature, indoor tests of rock-like specimens with an arc-shaped ice-filled flaw (Type-I) under uniaxial compression were performed in this paper, and the results were compared with those of flawed specimens Type-II (at 25 ℃ and without filled ice in the flaw). The results indicated that low temperature, flaw morphology and the presence of ice-filled flaw have significant effects on the mechanical properties. The overall peak stresses of Type-I specimens were larger than those of Type-II specimens, and the plasticity of the former one was significantly higher compared with that of the latter one. Meanwhile, the existence of filled ice resulted in significant differences in the failure characteristics between two types of specimens. The failure forms of Type-I specimens were dominated by tensile-splitting failure, while the failure forms of Type-II exhibited a tendency of varying with the flaw morphology. Combined with the macroscopic test phenomena, a water migration mechanism of water-saturated Type-I specimens was proposed, and the failure mechanism with the effect of frost heaving force under uniaxial compression was further analyzed in this paper.

Short-term O2/CO2 controlled atmosphere altered the water status and thus promoted phenolic biosynthesis during wound healing of fresh-cut white mushroom (Agaricus bisporus)

High O2/CO2 treatment has shown to promote the wound healing of fresh-cut white mushrooms. However, the mechanism of water migration in wound healing under high O2/CO2 treatment is still ambiguous. In this study, the effects of 80% O2 + 20% CO2 treatment before or after cutting on the accumulation of phenolic compounds, phenylpropanoid metabolism, as well as the water status and distribution in fresh-cut white mushrooms were evaluated. The results indicate that compared with the control group, both high O2/CO2 treatments before or after cutting increased the content of phenolic compounds, flavonoids and lignin. Among the high O2/CO2 treatments, the treatment after cutting stimulated the phenylpropanoid pathway, elevated the levels of individual phenols including protocatechuic acid, gallic acid, hydroxybenzoic acid, p-coumaric acid, cinnamic acid, ferulic acid, quercetin, catechin, and kaempferol. Additionally, with a longer storage time, the results of low-field nuclear magnetic resonance (LF NMR) indicate that the amplitude of free water significantly decreased and immobilized while the amplitude of bound water increased in all treatments. The moisture content in fresh-cut white mushroom mainly depends on the free water content. High O2/CO2 treatment after cutting maintained the level of free water inside while decreased the level of free water on the surface of fresh-cut white mushroom. In conclusion, high O2/CO2 treatments after cutting effectively enhanced wound healing by promoting the loss of surface water. Moreover, the wound healing on surface inhibited the water mobility and transformation inside white mushroom slices, this maintaining the quality of fresh-cut white mushrooms.

Water Migration and Segregated Ice Formation in Frozen Ground: Current Advances and Future Perspectives

A characteristic of frozen ground is a tendency to form banded sequences of particle-free ice lenses separated by layers of ice-infiltrated soil, which produce frost heave. In permafrost, the deformation of the ground surface caused by segregated ice harms engineering facilities and has considerable influences on regional hydrology, ecology, and climate changes. For predicting the impacts of permafrost degradation under global warming and segregated ice transformation on engineering and environmental, establishing appropriate mathematical models to describe water migration and ice behavior in frozen soil is necessary. This requires an essential understanding of water migration and segregated ice formation in frozen ground. This article reviewed mechanisms of water migration and ice formation in frozen soils and their model construction and introduced the effects of segregated ice on the permafrost environment included landforms, regional hydrological patterns, and ecosystems. Currently, the soil water potential has been widely accepted to characterize the energy state of liquid water, to further study the direction and water flux of water moisture migration. Models aimed to describe the dynamics of ice formation have successfully predicted the macroscopic processes of segregated ice, such as the rigid ice model and segregation potential model, which has been widely used and further developed. However, some difficulties to describe their theoretical basis of microscope physics still need further study. Besides, how to describe the ice lens in the landscape models is another interesting challenge that helps to understand the interaction between soil ice segregation and the permafrost environment. In the final of this review, some concerns overlooked by current research have been summarized which should be the central focus in future study.

Numerical simulation of water-gas two-phase displacement process in unsaturated granite residual soil

Infiltration of current in unsaturated soil is essentially a two-phase flow problem of water displacing air in the process of infiltration. The accuracy of traditional two-phase flow research methods cannot meet the needs of engineering, and it is not conducive to repetitive research. In contrast, the numerical simulation method of multiphase flow at the meso-scale can better simulate the whole dynamic process of water flooding. Mao Huan, Qren and others have achieved great results in the field of pore meso-scale research, but on the one hand, most of them focus on the study of rock multiphase flow, and there are some differences between the research object and the actual pore structure. On the other hand, the widely used pore network model method cannot directly show the change of particle velocity at any time and cannot present the phase interface movement state. In view of this, in order to reveal the dynamic percolation mechanism of water-gas two-phase displacement of unsaturated granite residual soil, this paper selected undisturbed granite residual soil in Fuzhou as the research object and studied the dynamic characteristics of two-phase displacement of undisturbed soil samples by using industrial CT scanning images and Level Set method. The results show that the Level Set method can properly capture the interface position between two immiscible fluids for meso-scale water-gas two-phase displacement simulation. The water-gas two-phase displacement process has the characteristics of large pore preferential flow, and the ‘low around’ phenomenon can easily appear in the higher ground of porosity roundness in general. The displacement rate is mainly controlled by the tortuosity of the channel, displacement speed is relatively high in the straight and wide channel. There is an obvious phenomenon of ‘preferential passage’, and its seepage time is positively correlated with the first rapid and then slow characteristics, and the maximum and minimum growth rate are 10.77 % and 1.90 %, respectively. The velocity distribution of the pore cross-section is related to the pore structure, and the phenomena of 'reflux' and 'flow around' cause the displacement velocity to drop sharply, whose decreasing degree can reach 21.62 %. The maximum displacement resistance appears at the hole wall, and the narrower the hole, the greater the resistance. The displacement efficiency is directly proportional to the displacement pressure difference, and the initial pressure growth effect is significant (up to 25.49 %, and only 1.47 % later). The research results can provide a theoretical basis for the study of the water migration mechanism of porous slopes, and also can enrich the theoretical basis of rainfall-induced landslides and are helpful in preventing natural disasters.

The effect of horizontal freezing on the characteristics of water migration and matric suction in unsaturated silt

Existing research on the mechanism of water migration during horizontal freezing is limited. Available freezing models are mainly applicable to saturated soils subjected vertical freezing and cannot accurately describe the coupled water-heat movement in unsaturated soils. In this paper, based on the Dallavalle formula and Young-Laplace equation, the Smith empirical formulation is used to establish a link between the macroscopic and microscopic water content of the frozen soil, and derive an analytical relationship between the matric suction and unfrozen water content of frozen soil. The formula is simplified to deduce the matric suction of unsaturated silt during horizontal freezing. A laboratory horizontal freezing experiment is carried out to explore the characteristics of the freezing process. The model established for the unsaturated freezing soil is subsequently improved by incorporating the relationships between matric suction, pore ice content, temperature, and unfrozen water content in the model. Using the model, the coupled water-heat movement during horizontal freezing process can be accurately described, and a typical case is analyzed to explore the interactions of temperature, unfrozen water, ice, and matric suction. In addition, the influence of the temperature gradient and initial water content on the freezing process characteristics is studied.

Evaluation of wheat flour substitution type (corn, green banana and rice flour) and concentration on local dough properties during bread baking

Different bread formulations, which provide different dough structures, were studied in order to better understand the effect of wheat flour substitution, flour type and concentration on dough development during baking, and their relationship with physical properties of the final product. Breads were produced with partial substitution of wheat flour by corn (CF), green banana (GF) and rice flour (RF), at different concentrations, and then baked at different times. Wheat flour substitution by CF, GF and RF in bread reduces heat transfer to the dough center by about 21%, 35% and 20%, respectively; and the water loss by about 5%, 15% and 0%, respectively. Those reductions were more influenced by flour type, than flour concentration. When wheat flour is substituted, the mechanisms of water migration are modified, once the pore system of bread dough is more discrete and stiffens later. Calculated thermal conductivity and diffusivity of the different flours used, and its correlations with average composite-bread heating rates (0.93) and water loss (0.85), respectively, indicates that thermal properties of composite bread dough could represent an important issue to be explored in dough systems with reduced gluten concentration.

An apparatus for measuring water content of unsaturated soil based on the van der Pauw principle

Understanding water migration in soil specimens under triaxial test conditions is of great significance for investigating the mechanism of distress in railway subgrades. However, the water content distribution along the specimen height is difficult to determine with current equipment. Motivated by such limitations, we developed an apparatus relying on the van der Pauw principle, to measure the water content based on the specimen’s electrical properties. Additionally, a series of exploratory tests on unsaturated soil specimens were conducted to evaluate the performance of this apparatus. To verify the practicability of the apparatus, a water-supply dynamic triaxial test was also carried out with an unsaturated dynamic triaxial test system (GDS). The results indicate that this apparatus is stable, as the measurement accuracy is not influenced by the electrode position or the soil geometry or dimensions. In a narrow triaxial pressure chamber, this apparatus can be used to determine the distribution of water content in unsaturated specimens nondestructively and consecutively during a triaxial test. The maximum error obtained from the apparatus when measuring the gravimetric water content was 0.7%. The soil resistivity calculation function was obtained considering the dry density and gravimetric water content with high correlation and precision. This apparatus has broad applications for investigating the mechanism of water migration within some geotechnical materials.

Ice lens induced interfacial hydraulic resistance in frost heave

Frost heave and ice lens cause the failure of engineerings and change the soil structure in cold regions. It is known that the water migrates from the unfrozen zone to feed the ice lens, but the mechanism of water migration in the vicinity of the ice lens is not well understood. In this study, the water migration at the interface between the ice lens and soil particles is theoretically investigated. Pore water flows from the soil pores to the unfrozen film between the ice lens and soil particles to expands the integral ice lens. The kinetics of the microscopic flow in the unfrozen film produces the hydraulic resistance at the macroscopic interface between ice lens and soil particles. Based on the global mechanical equilibrium at the ice-water interface, the rate of frost heave is derived for freezing soils with and without a frozen fringe. An expression for the neutral stress in the frozen fringe is developed to predict the initiation of new ice lenses with considering the effect of anisotropic stress of ice. The impacts of overburden pressure, temperature gradient, and interfacial hydraulic resistance on the rate of frost heave are discussed. In a relatively thick frozen fringe, the interfacial hydraulic resistance is insignificant compared to the hydraulic resistance of frozen fringe. However, if the thickness of frozen fringe is less than a critical value the interfacial hydraulic resistance will play a dominant role in the frost heave. This research is expected to facilitate the improvement of frost heave models, studying the influence of the interfacial hydraulic resistance on the characteristic of frost heave with and without a frozen fringe.

Measurement and analysis of the yearly characteristics of deep-buried phreatic evaporation in a hyper-arid area

Water scarcity is the primary cause of land deterioration, so finding new available water resources is crucial to ecological restoration. We investigated a hyper-arid Gobi location in the Dunhuang Mogao Grottoes in this work wherein the burial depth of phreatic water is over 200m. An air-conditioner was used in a closed greenhouse to condense and measure the yearly amount of phreatic evaporation (PE) from 2010 to 2015. The results shown that the annual quantity of PE is 4.52mm, and that the PE has sinusoidal characteristics. The average PE is 0.0183mmd−1 from March to November. Accordingly, by monitoring the annual changes in soil-air temperature and humidity to a depth of 5.0m, we analyzed the water migration mechanism in the heterothermozone (subsurface zone of variable temperature). The results show that, from March to November, the temperature and absolute humidity (AH) increase. This is due to the flow of solar heat entering the soil — the soil subsequently releases moisture and the soil is in a state of increasing AH so that evaporation occurs. From November to March, the temperature decreases. Now, the soil absorbs water vapor and AH is in a state of decline. Thus, it is temperature alternation in the heterothermozone — due to solar heat transfer — that provides the main driving power for PE. When it drives water vapor to move downwards in the heterothermozone, a small part is reversed upwards and evaporates. Solar radiation intensity dominates the annual sinusoidal PE characteristics.

Experimental investigation on water migration mechanism of macroporous silica gel in the coupling process of moisture adsorption and electro-osmosis regeneration

Electro-osmosis regeneration (EOR) of solid desiccant is a promising alternative method for dehumidification. Macroporous silica gel (MSG) has good performance on both moisture adsorption capacity and EO effect. In this paper an experimental bench is set up to investigate the water migration character and mechanism between the air and MSG in the coupling process of moisture adsorption and EOR. Through several continuous and oft-repeated experiments under different voltages, the experimental results validate that water can be transferred to a higher relative humidity environment through MSG by EO effect. It is found that the saturated water content around the anode decreases about 1.71% and 2.76% after twice EOR processes respectively. This phenomenon means the moisture re-adsorption capacity of MSG around the anode gets weaker after EOR. Based on the experimental results, the water migration mechanism of the coupling process is analyzed. Moreover, EO effect of MSG is studied from a new perspective. The water mass induced by EO has a near linear relationship with the electric charge transport with a certain EO starting value. The coefficient between the migration water mass and quantity of electric charge is about 0.0536g/C under the experimental condition.

Impact of osmotic pressure and gelling in the generation of highly stable single core water-in-oil-in-water (W/O/W) nano multiple emulsions of aspirin assisted by two-stage ultrasonic cavitational emulsification

The present investigation focuses in investigating the effect of osmotic pressure, gelling on the mean droplet diameter, polydispersity index, droplet size stability of the developed novel Aspirin containing water-in-oil-in-water (W/O/W) nano multiple emulsion. The aspirin-loaded nano multiple emulsion formulation was successfully generated using two-stage ultrasonic cavitational emulsification which had been reported in author's previous study. The osmotic behavior of ultrasonically prepared nano multiple emulsions were also examined with different glucose concentrations both in the inner and outer aqueous phases. In addition, introducing gelatin into the formulation also observed to play an important role in preventing the interdroplet coalescence via the formation of interfacial rigid film. Detailed studies were also made on the possible mechanisms of water migration under osmotic gradient which primarily caused by the permeation of glucose. Besides, the experimental results have shown that the interfacial tension between the two immiscible phases decreases with varying the composition of organic phase. Although the W/O/W emulsion prepared with the inner/outer glucose weight ratio of 1–0.5% (w/w) showed an excellent droplet stability, the formulation containing 0.5% (w/w) glucose in the inner aqueous phase appeared to be the most stable with minimum change in the mean droplet size upon one-week storage period. Based on the optimization, nano multiple emulsion droplets with the mean droplet diameter of around 400nm were produced using 1.25% (w/w) Span 80 and 0.5% Cremophore EL. Overall, our investigation makes a pathway in proving that the use of ultrasound cavitation is an efficient yet promising approach in the generation of stable and uniform nano multiple emulsions and could be used in the encapsulation of various active pharmaceutical ingredients in the near future.

Effect of Water Migration between Arabinoxylans and Gluten on Baking Quality of Whole Wheat Bread Detected by Magnetic Resonance Imaging (MRI)

A new method, a magnetic resonance imaging (MRI) technique characterized by T(2) relaxation time, was developed to study the water migration mechanism between arabinoxylan (AX) gels and gluten matrix in a whole wheat dough (WWD) system prepared from whole wheat flour (WWF) of different particle sizes. The water sequestration of AX gels in wheat bran was verified by the bran fortification test. The evaluations of baking quality of whole wheat bread (WWB) made from WWF with different particle sizes were performed by using SEM, FT-IR, and RP-HPLC techniques. Results showed that the WWB made from WWF of average particle size of 96.99 μm had better baking quality than those of the breads made from WWF of two other particle sizes, 50.21 and 235.40 μm. T(2) relaxation time testing indicated that the decreased particle size of WWF increased the water absorption of AX gels, which led to water migration from the gluten network to the AX gels and resulted in inferior baking quality of WWB.

Water migration mechanisms in amorphous powder material and related agglomeration propensity

The agglomeration phenomenon of amorphous particulate material is a major problem in the food industry. Currently, the glass transition temperature (Tg) is used as a fundamental parameter to describe and control agglomeration. Models are available that describe the kinetics of the agglomeration process as a function of the distance of the material from Tg (i.e. T−Tg). In practice these models are often not applied because they assume that the powder material is instantly in equilibrium with the humidity conditions of the environment and that solid mobility only occurs at T>Tg. Insights in the kinetics and mechanisms of water transport in powder material can help to better understand and control powder agglomeration. For this purpose, gravimetric step-change water sorption experiments were performed on maltodextrins as a function of the water activity aw. The maltodextrins vary in dextrose equivalents (DE), particle size and morphology. The experimental results were compared with a Fickian diffusion model in order to understand the dependency of the transport mechanism on water concentration gradient and material relaxation. The water transport kinetics in the maltodextrins with low DE (i.e. 6) were well described by Fickian diffusion for low aw, independently of particle size and morphology, until relaxation phenomena started to occur at an aw corresponding to T−Tg=−20°C. The importance of the matrix relaxation phenomena on the water transport mechanism increased with increasing DE (i.e. 29 and 32), not showing any relationship with the Tg. The results of this study indicate that the water migration mechanism is controlled by relaxation phenomena when the amorphous material is still far from the glass–rubber transition. The T−Tg at which the relaxation phenomena occur depends on the material. On the contrary, the T−Tg parameter could well describe the onset of agglomeration, independently from the material properties. Therefore, it can be concluded that within the conditions of this study, matrix relaxation occurring far below Tg did not affect the onset of agglomeration.

Centrifuge Modeling of Seismically Induced Uplift for the BART Transbay Tube

The BART Transbay Tube (TBT) is an immersed cut-and-cover subway tunnel that runs from Oakland to San Francisco, California. The loose sand and gravel backfills placed around the tunnel are considered to be liquefiable, and the clays under the backfill are soft in some zones along the alignment. These conditions could potentially result in uplift of the tunnel during strong earthquake shaking. This paper describes centrifuge model tests performed to verify numerical methods used to assess the stability and to evaluate the potential uplift mechanisms of the TBT. The observed mechanisms of uplift were a ratcheting mechanism (sand migrating under the tunnel with each cycle of relative movement), a pore water migration mechanism (water flowing under the tunnel), and a bottom heave mechanism, involving soft soils below the base of the trench. A fourth potential mechanism, viscous flow of liquefied soil, was not observed. The volume of the tunnel relative to the volume of the trench and the densities and permea...