Water Absorption Process Research Articles

Influence of Water Content on the Mechanical Characteristics of Mudstone with High Smectite Content

Water content plays an important role in strength of mudstone; many works pay more attention to the strength of dry and saturated rocks. In this study, the water absorption characteristics of mudstone were obtained by a computer-automated WA (water absorption) equipment system experiments. The complete stress–strain curves and UCS (unconfined compress strength) and E (Young’s modulus) of mudstone samples under different water contents were achieved by using the WEP-600 microcomputer-control screen universal testing machine. SEM (scanning electron microscope) test were carried out to study the microstructure characteristics of mudstone samples under different water contents. The results showed that the water absorption process of mudstone consists of three stages. The UCS and E of the mudstone samples markedly decrease with water content increasing. Based on the experimental results and analysis, a porous medium mechanical model of the mudstone was established and a deeper understanding of water-induced strength damage mechanism of the mudstone was achieved.

Electrochemical impedance spectroscopy characteristic of degradation process for carbon fiber/vinyl ester composites in salt water

The Electrochemical impedance spectroscopy of the T700/VE (vinyl ester) carbon fiber composite in 3.5% NaCl solution under open circuit potential (OCP) and cathodic polarization (−0.6 VSCE and −1.2 VSCE) conditions were studied, the moisture absorption was evaluated by weight gain test, and the degradation process was analyzed combined with scanning electron microscope. The T700/VE composite has very good resistance to degradation under OCP condition for long time (205 days) immersion, with about 0.38% moisture uptake and a slight decrease of low-frequency impedance (| Z|0.01 Hz). Cathodic polarization remarkably promotes the diffusion of moisture and ions in the resin matrix, the de-bonding between resin and carbon fibers, and characteristic of a porous electrode occurrence with a very quick decrease in | Z|0.01 Hz value. The variation of | Z|0.01 Hz is negatively correlated with the moisture absorption under OCP and −0.6 VSCE polarization conditions. So, | Z|0.01Hz may be used to monitor the water absorption and degradation process of the composite.

Establishing regularities of wood protection against water absorption using a polymer shell

This paper has analyzed protective materials for timber building structures and established the need to devise reliable methods for studying the process of water absorption by the surface of the construction structure necessary for designing new types of fire-retardant materials. Therefore, it becomes necessary to determine the conditions for the formation of a barrier for water absorption and to elucidate a mechanism for inhibiting the transfer of moisture to the material. In this regard, a mathematical model of the intensity of water mass transfer when using a polymer shell made of organic material as a coating has been built, which makes it possible to assess the effectiveness of the polymer shell by the amount of water absorbed. Based on the experimental data and theoretical dependences, the intensity of absorption of water by wood was calculated; and it has been established that the protective coating reduces the amount of water absorbed by more than 20 times. The results of determining the weight gain by a sample during water exposure indicate an ambiguous impact of the nature of protection on water absorption. In particular, this implies the presence of data sufficient for the qualitative process of inhibition of moisture diffusion; and detecting, on its basis, the point in time when the drop in the coating's efficiency begins. Analysis of the results of experiments reveals that the maximum increase in mass in the case of water absorption by a non-treated sample of wood was 40 % while the increase in the mass of wood samples treated with mixtures of oil and paraffin was less than 28 %. At the same time, the best protection is shown by a mixture of oil with paraffin within 90÷95 %. Thus, there are grounds to assert the possibility of directed regulation of wood protection processes through the use of polymer coatings that can form a protective layer on the surface of the material, which inhibits the rate of absorption of water.

Process and mechanisms of multi-stage water sorptivity in hydrophobic geopolymers incorporating polydimethylsiloxane

Geopolymers as emerging green cementitious materials have attracted much attention, while they can be infiltrated by water involving harmful ions due to their hydrophilic matrix and porous structure. In this work, metakaolin-based geopolymers that hydrophobically modified by polydimethylsiloxane (PDMS) were comprehensively investigated in terms of integral wettability, pore structure, and water sorptivity kinetics. Results demonstrate that an ultra low sorptivity stage occurs at the beginning of the water absorption process for hydrophobic geopolymers, which is derived from the change in pressure drop caused by the PDMS layer on pore walls. Although the low sorptivity stage is temporary due to continuous moisture diffusion, it is of great significance for the application of geopolymers in waterproof engineering. The hydrophobic matrix (contact angles: ∼130°) and the improved pore structure jointly contribute to low water sorptivity and transport of modified geopolymers. Moreover, a multi-stage water sorptivity model was established to further explain the sorptivity process and its mechanisms.

Antibiotic of tetracycline can delay water absorption and germination of Brassica seeds even at low concentrations and it is dependent on seed inherent characteristics.

Processes of seed water absorption and germination are critical for seedling establishment. To investigate the effect of tetracycline (TC), a major-use antibiotic, at low levels (1-5nM) on the two processes, we selected two sensitive species of Brassica seeds, including Chinese cabbage (Brassica rapa L.) and edible rape (Brassica napus L.), to establish the models of seed water absorption and germination. And every species of the seeds has two cultivars with different initial germination time used for studying. In the experiment at seed water absorption process, results showed that TC retarded the process at ≥ 1nM, but it depended on seed cultivars for all species. However, the surface structure of seed coat was not related to seed water absorption. In the experiment at seed germination process, results showed that TC delayed the process at ≥ 1nM, and it depended on seed cultivars for Chinese cabbage but edible rape. Because the longer the duration of the seeds being exposed to TC, the more susceptible the seeds were to TC. Moreover, the results of correlation analysis indicated that the effect of TC on seed water absorption at the early stage would influence that on seed germination at the later stage. It should be paid attention on the negative effects of TC at environmental levels on plants during early development stages which were revealed in our study.

Thermosensitive methylcellulose spray-dried microcapsules as a controlled release carrier for soil management

The excessive use of chemical products in agricultural production has brought many problems such as water pollution, air pollution, soil acidification and eutrophication of water bodies. Biodegradable methylcellulose microcapsules are used as carriers to achieve pollution-free and intelligent controlled release of agricultural chemical products. Methylcellulose was used as a coating material, loaded with fulvic acid (FA) and attapulgite (ATP), and then prepared into microcapsules by spray drying. The preparation process had good repeatability, and the obtained microcapsules possessed uniform particle size distribution. Methylcellulose microcapsules showed good heat sensitivity during water absorption process. The water absorption ratio was more than 10 times that of its own weight at 25°C, and the swelling ratio was 5–7 times that of its own weight at 35°C. The microcapsules reduced the loss of FA nearly 50% during the leaching process. Planting experiments showed that the microcapsules had good biocompatibility and exhibited obvious positive effects on the wheat growth.

Performance of Densified Wood Glulam as Building Bio-Material

In this research, some practical aspects of densified wood glulam were investigated. For this aim, poplar wood specimens were densified by hygro-thermo-mechanical technique. Glulam specimens were produced by finger joint technique and polyurethane glue was used as resin. Physical and mechanical properties of glulams were investigated according to ASTM D 143-09, ASTM D 905-03 and ISO 8375 standards. Based on obtained results, using this process (steam and pressurize compaction) resulted in improvement of physical and mechanical properties of glulam specimens. Optical microscopic and scanning electron microscopic (SEM) pictures were proved structural changes on wood material during of applied technique. Generally, the increase of wood density and hygrothermal treatment has a positive role on the glulam properties especially its dimensional stability. This technique showed a significant effect on water absorption; the steaming temperature and holding time significantly decreased water absorption but densification process increased this parameter. Also, delamination of specimens was decreased by hygrothermal treatment while densification showed negative effect on delamination. Moreover , modulus of rupture, modulus of elasticity, shear strength and compression strength parallel to grain were decreased by this technique but it is depend to treatment temperature and holding time. Higher temperature and holding time cause to higher decrease in the glulam mechanical strength.

Conductivity of polymer films formed by PEO-containing intramolecular polycomplexes

Block copolymers comprising chemically complementary poly(ethylene oxide)/polyacrylamide have been evaluated as proton conducting materials. With this aim in mind, two series of block copolymers PAAm-b-PEO (DBC) and PAAm-b-PEO-b-PAAm (TBC) with the variable PEO-block length have been synthesized. Polymer electrolyte membranes (PEM) based on DBCs, TBCs and also their partially hydrolyzed derivatives (DBChydr and TBChydr respectively) were prepared by using a solution casting technique, and their ion (proton) conductivity was studied at the ambient temperature and at different relative humidity (RH). The rise in RH from 33% to 98% resulted in the increase in conductivity of DBC and TBC membranes up to 10−4 S∙cm−1. The study of the kinetics of the water absorption at 98% RH showed that the introduction of –COOH-groups into PAAm chains could accelerate the process of water absorption. The increase in conductivity of DBC and TBC membranes with the PEO-block lengthening has been noticed. This proved the significant contribution of oxyethylene chains in ensuring the conductivity. The reason for the application of DBCs and TBCs as potantial ion-conducting membranes have been discussed.

Simplified hygromechanical coupling model and numerical simulation analysis of fibre reinforced composite deep-sea and underwater structures

The water absorption of composites will affect the safety and performance of the structure, resulting in the inability to give full play to its excellent lightweight and high-strength characteristics. This key issue is currently being experienced by composite deep-sea and underwater structures. The water absorption of composites is a complex problem involving the coupling of multiple scales. At present, the expressions of some water absorption theories are generally more complicated, which makes it impossible to apply the theories directly to the design and verification of deep-sea and underwater structures. This research assumes the uniformity of fibre distribution, with cylindrical-cube unit cells as the research object. A simplified hygromechanical coupling model of composites was proposed. Furthermore, by adding subroutines and considering the uneven distribution of the diffusion coefficients of each layer, the finite element method was used to simulate the whole process of water absorption of the composite laminate. Finally, it is compared with the experimental results to verify the effectiveness of the simplified model. Based on this comparison, the water absorption distribution, diffusion coefficient and interlayer stress variation law of composites in different time periods are obtained.

Use of empirical and diffusion models in the description of the process of water absorption by rice

PurposeTo describe water absorption by the rice grains over time, diffusion and empirical models were used. Also, an optimization software was developed in this study to determine parameters and their uncertainties for the diffusion models (LS Optimizer, for partial differential equations). Parameters (and their uncertainties) for empirical models were determined by LAB Fit Curve Fitting Software.Design/methodology/approachHeat and mass diffusion phenomena are found in various processes of technological interest, including pasteurization, drying and water immersion of agricultural products, among others. The objective of this work was to study the process of water absorption by rice grains with and without husk, using diffusion and empirical models to describe the absorption kinetics. Rice grains were immersed (approximately 10 g for each experiment) in drinking water maintained at constant temperatures of 28, 40 and 50 C. In the experiments, the water contents absorbed by rice grains over time were obtained by the gravimetric method.FindingsAmong empirical models, Peleg was the most satisfactory to describe the kinetics of water absorption by rice without husk, while the Silva et alii model had the best statistical indicators for rice with husk. It was also verified that a diffusion model with boundary condition of the first kind showed the best (or equivalent) results in the description of all processes of kinetics of water absorption by rice grains, with and without husk. For grains without husk, the effective mass diffusivities were (1.186 ± 0.045) × 10−9, (1.312 ± 0.024) × 10−9 and (2.133 ± 0.028) × 10−9 m2 min−1, for the immersion temperatures of 28, 40 and 50C, respectively. For grains with husk, diffusivities were (0.675 ± 0.011) × 10−9 and (1.269 ± 0.017) × 10−9 m2 min−1, for temperatures of 28 and 50 C, respectively.Originality/valueThis work developed a solver for the diffusion equation in cylindrical geometry and presented the LS Optimizer software developed to determine differential equation parameters through experimental data sets.

Hybrid Treatment via MHz Acoustic Waves and Plasma to Enhance Seed Germination in Mung Bean.

We investigate a hybrid treatment-consisting of an atmospheric pressure plasma pretreatment, followed by an MHz surface acoustic waves (SAWs) treatment with either de-ionized (DI) water or plasma activated water (PAW)-on mung beans to accelerate the germination process, as mung bean sprout is one of the important food staples. For the early growth rate (after 320 min), we observe that the hybrid treatment with PAW can lead to approximately 217% higher moisture content for the treated beans when compared with that without hybrid treatment. Additionally, the hybrid-treated beans germinate in around 120 min, while the untreated beans germinate only in around 420 min, that is, 3.5-fold faster for treated beans. This can be attributed to the dominant effect of SAW that accelerates stage 1 water absorption process and the effect of direct plasma and PAW that promote stage 2 metabolism process, leading to the enhancement in stage 3 germination process in early growth rate. For the post growth rate (after 24 h), we observe that the hybrid treatment with DI water can lead to an approximately 44.20% in higher moisture and 71.17% in radicle length when compared with untreated beans. Interestingly, the hybrid treatment with PAW, on the other hand, is observed to have an adverse effect on germination after 24 h, that is, approximately 14.51% lower in moisture content and 43.49% lower in radicle length for the hybrid-treated beans with PAW when compared with that with DI water.

Study on the influence of sample size and test conditions on the capillary water absorption coefficient of porous building materials

Capillary water absorption coefficient is one of the important wet parameters that characterize the liquid water absorption capacity of porous building materials. Relevant standards uniformly stipulate the size and test conditions of the specimen in analysis of this hygrothermal parameter for porous building materials. However, different porous building materials have different water absorption capabilities due to their pore structures. Therefore, the use of the same test conditions or standards when obtaining the capillary water absorption coefficient of the material will affect the accuracy of the obtained results. In this paper, an experiment with capillary water absorption was performed to study the influence of sample size, ambient temperature and water immersion depth on the capillary water absorption coefficient of foamed cement (FC), aerated concrete (AAC) and coral sand concrete (SHS) with different pore structures. The results show that the sample size and the depth of water immersion have a significant influence on the capillary water absorption coefficient value of FC; the ambient temperature has a significant influence on the capillary water absorption coefficient value of AAC. When temperature increases from 5°C to 35°C, the growth rate of the AAC capillary water absorption coefficient is about 71.3%. The depth of water immersion significantly affects the capillary water absorption coefficient value of the SHS. When the depth of water immersion increases from 3 mm to 10 mm, the growth rate of the SHS capillary water absorption coefficient is about 38.4%. ∙ Analyze the water absorption process of different pore materials. ∙Analyze the data processing method of capillary water absorption coefficient in different water absorption processes of materials. ∙Analyze the influence of sample size, ambient temperature, and water immersion depth on the capillary water absorption coefficient of different pore materials. ∙Weight analysis of factors affecting the capillary water absorption coefficient of different porous building materials. ∙Provide sample size, ambient temperature, water immersion depth and other experimental conditions and data processing methods for the determination of the capillary water absorption coefficient of different porous building materials.

Poly(lactic acid)-Poly(butylene succinate)-Sugar Beet Pulp Composites; Part II: Water Absorption Characteristics with Fine and Coarse Sugar Beet Pulp Particles; A Phenomenological Investigation.

Sugar beet pulp (SBP) is a residue available in large quantities from the sugar industry, and can serve as a cost-effective bio-based and biodegradable filler for fully bio-based compounds containing bio-based polyesters. The composition of SBP is characterized by an unusually high content of pectins, which are known as water-binding substances. Their molecular structure and the poor gelling properties, compared to other pectin sources, do not allow industrial use on a larger scale. However, good water absorption capacity can be advantageous for promoting plastics degradation or disintegration in the environment. In this study, we evaluated the water absorption capacity and processes of SBP-filled composites with bio-based polyesters on a longer time scale. We analyzed water absorption from a phenomenological point of view and tried to derive basic parameters for the general description of the composites behavior. We found that polar polyesters or polyester blends filled with higher amounts of especially coarse SBP suffer disintegration within a few weeks when supplied with sufficient water. On the other hand, less polar polyesters filled with fine SBP rather absorb water but do not show disintegration for several months. On a time scale of a few years, catalytic disintegration of the composites appears to be independent of the addition of SBP.

Synthesis of dual pH‐ and temperature‐sensitive poly(N‐isopropylacrylamide‐co‐acrylic acid)/sewage sludge ash hydrogel with the simultaneously high performance of swelling and deswelling

AbstractAn advanced dual pH‐ and temperature‐sensitive hydrogel (NASH2.5) was optimally synthesized through modification of N‐isopropylacrylamide (NIPAM) hydrogel with introducing 5 mol% acrylic acid (AA) and 2.5 wt% sewage sludge ash (SSA). The swelling kinetic results showed that NASH2.5 exhibited both high equilibrium swelling ratio and swelling rate, which was attributed to the higher porous structure as shown in scanning electron microscope, and the more hydrogen bonding formed inside of the hydrogel as investigated in Fourier transform infrared spectrometer. In addition, its curve was better fitted to the pseudo‐second‐order model, indicating that the water absorption process was dominated by chemisorption through forming the hydrogen bonding among the water molecules and carboxyl/silanol groups of the hydrogel. Compared with the pure NIPAM hydrogel, the water transport mechanism switched from Case I diffusion to Case II diffusion by introduction of AA and further SSA. Furthermore, through the results of the deswelling kinetics in pH value change (from 9 to 4 and 2, respectively), temperature value change (from 25 to 40, 50, and 60°C, respectively), and dual pH and temperature values changes, NASH2.5 not only presented a high pH sensitivity, but also showed high sensitive to temperature by achieving high water recovery ratio in rapid dehydrated rate. Therefore, the dual stimuli‐sensitive hydrogel with the simultaneously high performance of swelling and deswelling would provide a suitable alternative for specific applications such as pollutant adsorption.

Theoretical analysis of water absorption kinetics of recycled aggregates immersed in water

Water absorption kinetics of recycled aggregates (RAs) is closely connected with the effective water to cement ratio (w/c), which influences the workability of concrete mixture and the performance of hardened concrete. However, experimental methods are talentless to uncover the detail of the process, especially the initial stage of the water absorption of RAs. In order to explore the mechanism of water absorption of RAs, theoretical analysis is conducted based on the experimental data. Firstly, a non-uniform cross-sectional capillary tube is introduced to investigate the mechanism of water–air displacement in RAs, which are immersed in water. Secondly, based on the Terzaghi capillary water rise model, a theoretical model is established to describe the initial stage of water absorption of RAs. Thirdly, the mechanism of water absorption of RAs during the second stage (slow water absorption stage) is analyzed theoretically. The results show that the process of water absorption of RAs can be divided into two stages: rapid water absorption stage and slow water absorption stage. The rapid water absorption rate during the first stage is caused by the high capillary pressure in small pores and large contact area of RAs with water. The slow water absorption rate during the second stage is mainly caused by two reasons: the bubbles adhered on the surfaces of RAs are not separated timely and the capillary pressure in big pores, which act as the exhaust passage during the first stage, is low.

Diffusion and kinetic modeling of water absorption process during soaking and cooking of chickpea

AbstractThe chickpea soaking and cooking processes were empirically studied in terms of water absorption. The effective moisture diffusivity (Deff) and the convective mass transfer coefficient (K) were determined by developing a mathematical model in spherical coordinates. According to the evaluation of mass transfer parameters, the values of Deff and K ranged from 0.91 × 10−12 to 1.49 × 10−10 m2/s, and 2.02 × 10−10 to 7.25 × 10−10 m/s, respectively. Also, the kinetic behavior of chickpea during soaking and cooking was successfully modeled by the commonly used predictive models such as Peleg, Page, two‐term, and Vega–Lemus. The statistical parameters including the coefficient of determination (R2) and sum of square error (SSE) were applied for comparison of mathematical models. The two‐term model was found to be the best predictive equation for describing the soaking behavior of chickpea. In the case of cooking, a proposed model in this study was introduced as the best equation in predicting the moisture content of chickpea against time. The approach that was applied in this work can support the development of diffusion and kinetic modeling in different types of legumes during soaking, cooking, and the other processes related to moisture absorption or removal.

Indirect air CO2 capture and refinement based on OTEC seawater outgassing

SummaryIn this paper, we propose a low-cost method to capture and purify CO2 from ocean water indirectly from the atmosphere. Atmospheric CO2 dissolves in seawater following Henry's law. In open-cycle ocean thermal energy conversion (OC-OTEC), being a heat engine, large quantities of water are used to generate electricity from temperature differences in the ocean. CO2 and other gases dissolved in seawater are extracted from seawater by a vacuum compressor, being essential for heat transfer in OC-OTEC. Non-condensable gases containing CO2 from OC-OTEC are currently considered a waste gas stream. Based on literature, we calculate cold water non-condensables containing up to 14% CO2. These non-condensables can be refined further to 80–90% purity with a water absorption process, inspired by those as used in the biogas industry. Levelized CO2 capture and purification costs were estimated to be 15–35 euro per ton, as only refinement costs are allocated of a waste gas stream of OC-OTEC.

Implementation of capillary penetration coefficient on water sorptivity for porous building materials: An experimental study

Neutron radiography is used to study the relation between water sorptivities (s) and capillary penetration coefficient (k), and to reveal impacts of sealing method on the water absorption process in brick samples. Except for the ends, the samples' outer surfaces were coated with a polymeric waterproofing slurry. While the samples were absorbing water, neutron radiography images were recorded continuously. Analyses of the acquired images, as well as published results for construction building materials, were used to determine water sorptivities (s), capillary penetration coefficient (k), and capillary porosity (θc). The results showed that s is proportional to k in a direct manner, and that θc is the proportionality constant. It was found that samples coated with a polymeric waterproofing slurry absorb water more quickly than samples coated with acrylic paint.

An Evaluation of Water Absorption Process Parameters for Composites by Deploying A Novel DEMATEL Method-PROMETHEE Method

Parametric ranking and selection in water absorption process of composite development are obligatory as they guide on resource distribution during the planning phase of composite development. However, the present literature model seems inaccurate as the PROMETHEE method fails to offer the likelihood of structuring the water absorption problem making it challenging to achieve a concise problem viewpoint and assess the results without difficulty. In this paper, the DEMATEL method is introduced to assign weights, revealing a cause and effect mechanism to overcome the aforementioned problem. The coupling point of the DEMATEL method-PROMETHEE method is at the weight determination of the DEMATEL method and the net outranking results are the final output of the model. Based on literature data, the DEMATEL method produced weights of 0.182, 0.114, 0.290, 0.242 and 0.244 for the parameters of final weight, initial weight, length, thickness and time, respectively. The PROMETHEE procedure yields the outranking results of -0.2166, -0.2742 and -0.0079 for the length, thickness and time, revealing time as the best parameter. The proposed method is user-friendly, complete in outranking, successful in real-world applications and capable to establish the cause and effect series constituent of the complicated water absorption system. The usefulness of this research is to help composite developers to achieve effective distribution of resource and decision regarding priority of parameters, leading to lean and effective manufacturing outcomes.

An Implementation of A Combined DEA-PROMETHEE Method for The Hull of A Ship Application

The selection of an appropriate parameter in a water absorption process experiment is an important route to reducing fabrication wastes and ensuring the optimum deployment of scarce process resources to the appropriate parameter. However, the literature is inadequate in providing an appropriate direction on selecting parameters for the hull of the ships' application due to the conflicting requirements of the interested parties. A novel method called the Data Environment Analysis (DEA) to overcome this problem. Preference Ranking Organization Method for Enrichment of Evaluations (PROMETHEE) method is deployed to establish the appropriate parameter in a water absorption process on epoxy composite. The net outranking results show that criterion B (final weight) is placed in the first position. The criterion A (initial weight), D (thickness), and C (length) are placed in the second, third, and fourth positions, respectively, while E (time) is not necessary to the achievement of the system's goals. The key novelty is the unique application of the fused DEA-PROMETHEE method to a composite using the Taguchi signal-to-noise ratio response table for the hull of a ship. The method enhances the performance of multiple inputs (parameters) and multiple outputs (responses). The results of the DEA method-PROMETHEE method established the potential of epoxy composite to be used on the ship for the hull component. This could reduce the waste generated in the system, and guided allocation of resources are made to the appropriate parameters and, consequently, enhance the shipping company's profit. Furthermore, the results could improve the shipping vessel performance and develop a sustainable practice, which will lengthen the lifespan of the shipping industry.