Variations In Moisture Content Research Articles

Correlations between moisture expansion and flexural properties of bamboo strips in response to different loading rates

AbstractBamboo and bamboo products, known for their hygroscopic nature, exhibit sensitivity to different loading rates in dry conditions. However, with the increasing prevalence of heavy and extended precipitation events due to global warming, there is still a lack of investigation on the response of bamboo strips to various loading rates after being attacked by moisture. In this study, the bending properties of bamboo strips after exposure to extremely high-humidity environments were investigated to assess their responses to varying loading rates. Throughout different exposure durations, bamboo strips exhibited varying moisture contents up to 112% and evident volumetric moisture expansion. After moisture exposure, bamboo strips exhibited heightened sensitivity in flexural strength and modulus to loading rates, with the most pronounced sensitivity observed at 33.9% moisture content. In addition, a linear relationship was established between flexural strength loss and volumetric expansion rather than moisture content. Notably, the samples exhibited greater sensitivity in strength loss to moisture expansion under lower loading rates. These findings preliminarily elucidate how loading rates impact the mechanical properties of bamboo strips across varying moisture levels, contributing to understanding the deterioration in the properties of engineered bamboo products when exposed to high humidity and rainy environments with potential collision events.

Accuracy of hygro-expansive curl predictions for paper sheets based on homogenised 2D and 3D network representations

Paper, a porous-fibrous network, is made up of hydrophilic fibres, which are notably susceptible to deformations due to variations in moisture content. The response of paper sheets to full or partial wetting, based on the water-induced fibre swelling, has mostly been predicted in the past using highly idealised two-dimensional network geometries. The purpose of the present paper is to establish how precisely the two-stage process of determining effective hygro-expansivity under uniform wetting by a two-dimensional model followed by bending analysis using a continuum model predicts the curl of a fully three-dimensional network. In the present multi-scale modelling work, the moisture-induced homogenised sheet scale curl, derived from hygro-elastic deformations using non-uniform moisture profiles, is analysed based on an idealised non-woven three-dimensional fibrous network finite element model. First, the effective paper sheet swelling properties, derived computationally for the uniform wetting condition, are compared with analytically homogenised hygro-elastic properties. Whereas the analytically predicted elastic modulus has an inaccuracy of only ∼5%, the hygro-expansivity coefficient is over-predicted by roughly a third for a network with straight fibres. The difference is smaller if waviness of the fibres and wrap-around in the fibre bonds are taken into account. Fibre alignment turns out to have little influence. Subsequently, paper sheet curl predictions made by the analytical model are compared with that computed from the three-dimensional network model. The inaccuracy of the fully analytical model, based on the two-dimensional network description, relative to the fully detailed three-dimensional computational model with straight fibres is on the order of 40%–50%. The fidelity of the simple model is primarily constrained by the inaccuracy of the effective hygro-expansion coefficient. If the expansivity extracted from the three-dimensional simulations under uniform wetting is inserted, the inaccuracy drops to less than 10%. The continuum bending description hence performs adequately, provided it is based on a reliable estimation of the uniform expansion behaviour of the material.

Predicting biomass comminution: Physical experiment, population balance model, and deep learning

An extended population balance model (PBM) and a deep learning-based enhanced deep neural operator (DNO+) model are introduced for predicting particle size distribution (PSD) of comminuted biomass through a large knife mill. Experimental tests using corn stalks with varied moisture contents, mill blade speeds, and discharge screen sizes are conducted to support model development. A novel mechanism in the extended PBM allows for including additional input parameters such as moisture content, which is not possible in the original PBM. The DNO+ model can include influencing factors of different data types such as moisture content and discharge screen size, which significantly extends the engineering applicability of the standard DNO model that only admits feed PSD and outcome PSD. Test results show that both models are remarkably accurate in the calibration or training parameter space and can be used as surrogate models to provide effective guidance for biomass preprocessing design.

Effects of Soil Moisture Content Variations on Fruit Quality and Tree Stress in Satsuma Mandarin ‘Miyagawa Wase’ during Porous Sheet Mulching Cultivation

Effects of Soil Moisture Content Variations on Fruit Quality and Tree Stress in Satsuma Mandarin ‘Miyagawa Wase’ during Porous Sheet Mulching Cultivation

Effects of road- vs. field-recommended tyre inflation pressures and small variations in soil moisture content on traffic-induced soil compaction during seedbed preparation

Soil compaction has become one of the most common forms of soil degradation, with associated negative effects on the functioning of agricultural soils. Decades of research have led to publication of several practical measures that mitigate risk of soil compaction, yet adoption among European farmers remains limited. To improve adoption by farmers, experiments under practical conditions using common operations should be performed. A field experiment was set up to evaluate the effects of road- (200 kPa) vs. field- (140 kPa and 100 kPa) recommended tyre inflation pressure and soil moisture content (0.24 g g−1 vs. 0.22 g g−1) on traffic-induced compaction of a silt loam soil during seedbed preparation. The various tyre inflation pressures were tested using two tyre types (standard radial tyre at 200 kPa and 140 kPa; VF tyre at 100 kPa) of similar dimensions mounted onto the same tractor. Variation in experimental soil moisture content was achieved by performing the seedbed preparation on two dates in spring (early, March 30th, vs. late, April 14th). In this one-year study, reducing the standard-tyre inflation pressure from road- (200 kPa) to field-recommended (140 kPa) pressure did not prevent soil compaction. The use of VF tyres at field-recommended (100 kPa) tyre inflation pressure resulted in significant reductions in vertical contact stress and mean normal stress as compared to 200 kPa. Although non-significant, the pressure reduction from 200 kPa to 140 kPa did result in a 4 % increase in in-track dry matter sugar beet yield while a reduction from 200 kPa to 100 kPa resulted in an 11% increase. Lower tyre inflation pressure showed no significant effect on fuel consumption and penetration resistance. Seedbed preparation under slightly drier (0.22 g g−1) soil conditions negatively affected fuel consumption (+11 %) and resulted in an in-track dry matter sugar beet yield increase of 11 %. For both tested prevention strategies, the impact of soil compaction was better observable by sugar beet yield than by most of the measured soil physical parameters.

Resource utilization of gasified fine ash from entrained flow bed via thermal modification-melting combustion: A pilot study

China generates substantial quantities of gasified fine ash (GFA) annually through entrained flow bed coal gasification processes. These GFAs are laden with significant amounts of poorly reactive carbon and abundant ash resources, including silica, aluminum. Typically GFA represent not only a gross squandering of resources but also a potential source of environmental contamination. In order to use both ash and carbon of GFA, our team has developed the thermal modification -melting combustion method. The study conducted thermal modification-melting combustion experiments of GFA with auxiliary heating fuel and varying moisture content on a pilot-scale experimental platform. The aim was to ascertain the influence of operating conditions on the physical and chemical properties of GFA fuel, as well as the carbon conversion rate of GFA and the potential for reusing ash after melting combustion in the entire system. The results indicate that an increase in the moisture content of GFA allows the thermally modified fine ash (MFA) to possess smaller particle sizes and more reactive sites in carbon structures, along with higher combustible gas yield and calorific value. Post-melting combustion, the residual carbon conversion rate in GFA surpassed 96.88 %, indicative of a high recovery potential. Moreover, the ash slag, rich in inorganic non-metallic glassy phases, emerged as a promising candidate for material reuse and application.

Model Studies on Settlement of an Expansive Soil Slope Stabilized with GGBS

Expansive soils present significant challenges in civil engineering due to their tendency to undergo volumetric changes with variations in moisture content, often resulting in slope instability and settlement issues. This study investigates the effectiveness of stabilizing expansive soil slopes using Ground Granulated Blast Furnace Slag (GGBS) as an additive. The research employs laboratory-scale model studies to simulate the behaviour of expansive soil slopes subjected to varying levels of GGBS stabilization. The settlement characteristics of the stabilized slopes are analysed under different loading conditions and moisture contents. Experimental results indicate that the incorporation of GGBS enhances the properties of expansive soils, reducing settlement and improving slope stability. The findings contribute to the understanding of sustainable solutions for mitigating settlement issues in expansive soil slopes, offering insights for practical applications in geotechnical engineering.

Evaluation of the Effect of a Spray Coating Applied on Open-Air-Stored Woodchips

The present study aimed at testing the benefits of protecting woodchips with an acrylic crusting product developed for the coal energy industry. In the test carried out, four conical wood chips piles were built, two consisting of fresh biomass, the other two of dry wood chips. A fourth larger pile was built as a reference. One dry and one fresh pile were superficially treated with 25 kg of protective acrylic solution diluted in 250 L of water, providing an average application of coating agent of approximately 85 g m−2, while the other two worked as controls. To monitor the piles’ temperature variation, thermal sensors were placed in the inner part of the five piles during their construction. Moisture content (MC) and dry matter (DM) variations in woodchip piles were recorded. The piles treated with the coating agent did not show any significant differences with the untreated piles: in wet material, the protective film slightly reduced the moisture dispersal from the pile from evaporation rather than limiting water intake from rain; in dry material, this confirms the inability of the coating agent to limit water intake from rainfall.

Experimental and damage model study of layered shale under different moisture contents

To investigate the mechanical properties and damage evolution law of layered shale under varying moisture contents, we conducted triaxial compression experiments on rock samples with different bedding angles and moisture levels. This study analyzed the variations in mechanical properties of layered shale under different conditions, and established a predicted model for elastic modulus based on different bedding angles and moisture content. Additionally, the damage constitutive model of layered shale was improved. The study revealed that shale’s mechanical properties display anisotropy, which is influenced by the bedding angles and moisture contents. The elastic modulus of the rock increases with the rise of bedding angle, exhibiting a ‘U’-shaped change. Conversely, the mechanical properties of rocks deteriorate, and their brittleness weakens with the increase in moisture content. When the confining pressure increased, the overall mechanical properties of shale were enhanced, and the influence of bedding on shale was weakened, but the deteriorating effect of water on rocks was hardly affected. Based on the above experiments, a predicted model of equivalent elastic modulus of shale considering the coupling effect of bedding and different moisture contents was proposed, which could effectively predict the elastic modulus of layered shale with different moisture content under different confining pressures. Furthermore, based on the predicted model of elastic modulus, an improved damage constitutive model of layered shale under triaxial loading was established, and the damage accumulation trend of layered shale was obtained, which showed an “S”-shaped change with strain. Under the coupling effect of bedding and different moisture contents, the damage of shale was advanced, but the accumulation rate of damage slowed down. With the increase of confining pressure, the influence of bedding and moisture content on the damage characteristics of shale decreased, and the damage curves under different conditions gradually tended to isotropy. The developed damage constitutive model for layered shale under different moisture contents provides theoretical support for the study of reservoir fracturing and wellbore stability.

Monitoring cotton water status with microtensiometers

AbstractStem water potential (Ψstem) is a key indicator for assessing plant water status, which is crucial in understanding plant health and productivity. However, existing measurement methods for Ψstem, characterized by destructiveness and intermittency, limit its applicability. Microtensiometers, an emerging plant-based sensor, offer continuous monitoring capabilities and have shown success in certain vine and tree species. In this study, we investigate the efficacy of microtensiometers ability to monitor the Ψstem of cotton (Gossypium hirsutum L.) under three distinct irrigation treatments in Maricopa, Arizona, an extremely hot, arid environment. We analyze the diurnal dynamics of Ψstem across the irrigation regimes and compare these measurements with midday leaf water potentials (Ψleaf) obtained using a dewpoint potentiometer. Our results demonstrate that the microtensiometer-derived Ψstem closely follows known diurnal patterns of Ψleaf, tracking with vapor pressure deficit (VPD) and responding to variations in irrigation levels and soil moisture content. Time cross-correlation analysis reveals an 80-minute lag in Ψstem response to changing VPD under non-water limiting conditions, which shortens under water-limiting conditions. Additionally, we establish a robust linear relationship (R2adj = 0.82) between Ψstem and Ψleaf, with this relationship strengthening as water availability decreases. Notably, we observe mean gradients of 1.2 and 0.06 MPa between soil vs. stem and stem vs. leaf water potentials, respectively. Moreover, Ψstem data proves to be more sensitive in distinguishing between irrigation treatments earlier in the growing season compared to Ψleaf, leaf temperature and leaf gas exchange parameters. These findings highlight the utility of microtensiometers as valuable tools for monitoring water status in smaller-stemmed row crops such as cotton.

Assessment of Reclaimed Mined Area of Sahastradhara, Dehradun by Soil and Vegetation Analysis

This study investigates the impact of forest area mining on reclaimed limestone mined areas in Sahastradhara, Uttarakhand, India. Initiated in 1989-90, eco-restoration efforts aimed at rehabilitating the mined areas resulted in restoration ages of 25, 24, and 23 years across different sites. The study comprehensively examined vegetation and soil physicochemical properties at various depths, revealing the dominance of species like Murrayakoenigii, Acacia catechu, Vitex negundo, Eupatorium adenophorum, Grevillea robusta, and Lantana camara. Soil analyses unveiled variations in moisture content, bulk density, and coarse fragment percentage across the sites, a rise in organic carbon, phosphorous, and nitrogen levels, showcasing soil improvement post-restoration. Correlation analyses unveiled interrelationships between soil properties, emphasizing the importance of organic matter in influencing soil acidity. Vegetation analyses at different sites revealed evolving plant communities, with prominent species contributing to the ecological richness. The Importance Value Index (IVI) and Shannon Weiner Index (H') provided insights into species dominance and biodiversity. The results showed that the soil pH was slightly basic, and the available phosphorus and nitrogen levels were within the optimal range for plant growth. However, the bulk density and electrical conductivity values were higher than the recommended range. This study contributes valuable insights into the intricate interplay between mining activities, vegetation dynamics, and soil health, guiding future ecological restoration endeavors in similar contexts. The study concluded that the eco-restoration work carried out in the area has been successful in restoring the vegetation, but further assessment is required to ensure the long-term success of the restoration efforts.

Calibration complexities: full-scale error impact and simultaneous variation of salinity, temperature, and moisture content on sensor performance in soil

Calibration complexities: full-scale error impact and simultaneous variation of salinity, temperature, and moisture content on sensor performance in soil

Parameter study and identification of DEM modeling for varied sand moisture content based on bulldozing experiment

The discrete element method (DEM) has been widely used to simulate varied sand particles interacting with earthmoving machines. However, past research using DEM barely addressed accurate verification and validation for different sand moisture content. Therefore, the main purpose of this paper is to reveal the range of key parameters of an adhesive force model used in the DEM simulation corresponding to the specific sand moisture content. We considered the bulldozing phenomenon to be typical earthmoving work and performed the bulldozing experiments under different sand moisture levels to investigate the bulldozing force variations. Subsequently, the DEM simulation with an adhesive force model calculated the bulldozing force corresponding to the experimental results. The values for two adhesive parameters, i.e., a scaling magnitude and the maximum adhesive distance between particles, were adjusted such that the maximum bulldozing force calculated in the DEM coincides with that of the experiments under different moisture contents. The experimental verification of the DEM revealed the relationship curves between these two key parameters corresponding to the different moisture content. The relationship obtained in this paper implies that the DEM simulation carefully adjusting the adhesive force parameters can reproduce machine interaction on moist sand environments accurately.

Characterization and Simulation of the Interface between a Continuous and Discontinuous Carbon Fiber Reinforced Thermoplastic by Using the Climbing Drum Peel Test Considering Humidity.

The objective of this paper is to investigate the debonding behavior of the interface between continuously and discontinuously fiber reinforced thermoplastics using the climbing drum peel test. The study emphasizes on the importance of considering different climatic boundary conditions on the properties of thermoplastics. Specimens with varying moisture contents, from 0m.% up to above 6m.% are prepared and tested. It is observed that an increase in moisture content from 0m.% to 2m.% results in an increase of the fracture surface energy from 1.07·103J/m2 to 2.40·103J/m2 required to separate the two materials, but a further increase in moisture to 6.35m.% conversely results in a subsequent decrease of the required energy to 1.91·103J/m2. The study presents an explanatory model of increasing plasticization of the polymer due to increased polymer chain mobility, which results in more deformation energy being required to propagate the crack, which is corroborated in SEM investigations of the fracture surface. A further increase in humidity leads to polymer degradation due to hydrolysis, which explains the subsequent reduction of the fracture energy. The experimental set up is modeled numerically for the first time with cohesive surfaces, which could successfully reproduce the effective force-displacement curve in the experiment by varying the interface parameters in the model over an influence length, allowing the conclusion of a process induced variation in the interface properties over a specific consolidation length.

Study on interaction of Viscoelastic and Mechano-sorptive creep and effect of Fibre Reinforcement on creep of Timber beams

Timber is a sustainable material widely used in structural elements. Its viscoelastic nature, in which the stress-strain relation varies with time, poses significant challenge to the durability of timber structures. Creep of timber under constant loading depends on various factors like stress level, moisture content, load-to-grain angle, temperature, relative humidity etc. Among these, relative humidity and moisture content in timber are the most crucial. Drastically varying moisture content causes mechano-sorptive creep. However, the interaction and contribution of various factors causing creep is still a matter of research. Various codes provide generalized creep coefficient for long term deflection and load reduction factors. A detailed rheological model was proposed by Toratti which addresses mechano-sorptive creep explicitly, incorporating both recoverable and irrecoverable part in creep. This paper aims to review the study on interaction between viscoelastic creep and Mechano-sorptive creep in various environmental conditions. Effect of reinforcing timber beams, on the long term deflection due to creep is also made a subject of study to identify a possible solution to the accelerated deflection by Mechano-sorptive creep, which will be unavoidable in tropical areas with extreme climactic changes. A comparative study between the various standard codes with Indian Standard Codes for timber with respect to creep, is also made, to identify the gaps in IS codes.

Study on heat and moisture transfer of nonspherical rice during hot‐air drying in thin‐layer grain pile

AbstractTo investigate fluid flow and coupled heat‐moisture transfer in the hot‐air drying of grain piles, this study integrated the discrete‐element method with computational fluid dynamics. A model for a thin‐layer grain pile, consisting of nonspherical rice particles represented by 13 spheres, was developed. Using a heat‐moisture transfer model based on fluid–solid coupling, the drying process with hot air was simulated and validated against experimental data. Finally, by controlling the drying temperature and the initial moisture content of rice, the variations in temperature and moisture content during the hot‐air drying process were explored. The numerical results indicated that the nonuniform pore structure within the grain pile, gaps on the surface of nonspherical rice, and the wall effect led to complex airflow patterns, resulting in the formation of dead zones within the grain pile. The oscillation frequency and amplitude of radial porosity near the wall were relatively large, and the minimum porosity occurred at a radial distance of 1/2dg. Heat and moisture transfer rates between the rice and drying air were influenced by the temperature and moisture concentration differences. During the drying process, variations in temperature and moisture content were observed among rice particles. Limited by the moisture diffusion coefficient, there existed a notable disparity in moisture content between the interior and surface of the rice. The results also showed that the curvature of the drying curve in the grain pile varied and was influenced by the drying conditions, especially under the high‐temperature drying condition of 60°C.Practical ApplicationsIn this study, a grain pile model for nonspherical rice particles composed of 13 spheres was developed based on the discrete‐element method and computational fluid dynamics. Furthermore, in accordance with the heat and mass transfer mechanism of fluid–solid coupling, a heat‐moisture transfer model for the hot‐air drying of the grain pile was constructed. This was done to deeply explore the internal fluid dynamic characteristics and the heat‐moisture transfer within the grain pile during the drying process. The newly established model can be widely applied to numerical simulation studies of drying and also has reference value for the design of drying systems.

Permanent deformation characteristics of unsaturated subgrade soils under cyclic loading

Excess permanent deformation of subgrade may cause critical rutting in pavements, and subsurface water significantly affects the accumulation of permanent deformation. This study aims to reveal the permanent deformation behaviour of unsaturated subgrade soils. Subgrade box tests were performed at varying moisture content, stress levels and loading frequency, respectively. The test results show that the permanent deformation significantly increased with moisture content. The concept of a permitted moisture content-applied dynamic load envelope was proposed. Based on curve fitting, a prediction model of permanent deformation of subgrade soils was developed, and the effects of moisture content and loading cycles were included. The validation results show that the model exhibited reasonably good performance in modelling the deformation. This study may provide an alternative way for predicting the permanent deformation of unsaturated subgrade soils.

Thermal properties of a raw earth-flax fibers building material

The aim of this paper is to investigate the thermal behavior of composite building materials comprised of silt and flax fibers, considering various initial conditions. The experiments were conducted on flax fibers alone, examining factors such as moisture content variation, fibers arrangement, and density. Subsequently, the thermal properties of the earth-flax fiber composite were studied, taking into account the influence of water content and fibers mass content. The thermal properties of both flax fibers and raw earth-flax fibers composite specimens were determined using the experimental unsteady-state method. The results indicate that the thermal conductivity and heat capacity of flax fibers increase with density, temperature, and moisture content. Regardless of fibers density and arrangement of fibers, linear relationships have been established for both thermal conductivity and heat capacity as functions of temperature. Additionally, it was demonstrated that the heat capacity and the thermal conductivity increase with water content, regardless of the percentage of added fibers. Moreover, mixing randomly flax fibers with compacted raw earth material has improved the thermal properties of the composite. This improvement pertains to its insulating capacity, ability to store heat, and, subsequently, its contribution to the thermal comfort provided by such earth composite material when used as a building material.

Characterization of a Deglaciated Sediment Chronosequence in the High Arctic Using Near‐Surface Geoelectrical Monitoring Methods

ABSTRACTAccelerated climate warming is causing significant reductions in the volume of Arctic glaciers, such that previously ice‐capped bare ground is uncovered, harboring soil development. Monitoring the thermal and hydrologic characteristics of soils, which strongly affect microbial activity, is important to understand the evolution of emerging terrestrial landscapes. We instrumented two sites on the forefield of a retreating Svalbard glacier, representing sediment ages of approximately 5 and 60 years since exposure. Our instrumentation included an ERT array complemented by adjacent point sensor measurements of subsurface temperature and water content. Sediments were sampled at each location and at two more additional sites (120 and 2000 years old) along a chronosequence aligned with the direction of glacial retreat. Analysis suggests older sediments have a lower bulk density and contain fewer large minerals, which we interpret to be indicative of sediment reworking over time. Two months of monitoring data recorded during summer 2021 indicate that the 60‐year‐old sediments are stratified showing more spatially consistent changes in electrical resistivity, whereas the younger sediments show a more irregular structure, with consequences on heat and moisture conductibility. Furthermore, our sensors reveal that young sediments have a higher moisture content, but a lower moisture content variability.

Fuel Wood Pellets Produced from Sawdust of Scots Pine Mature and Juvenile Wood: Self-Heating and Off-Gassing Tests at Industrial Scale

AbstractThis study investigated self-heating and off-gassing of Scots pine (Pinus sylvestris) wood pellets made from sawdust generated from separated mature and juvenile wood. The pellets were produced at an industrial scale and stored in large piles of about 7.2 tonnes. The production process involved drying the sawdust using three different methods and to varying moisture contents. The results indicated significant influences of both raw material type (F(6) = 61.97, p < 0.05) and drying method (F(2) = 65.38, p < 0.05) on the self-heating of the pellets. The results from the multiple regression analysis further showed that both the raw material type and pellet moisture content significantly influenced the temperature increase, with strong correlations observed for pellets produced using low-temperature drying (F(3, 14) = 83.52, multiple R2 = 0.95, p < 0.05), and medium temperature drying (F(3, 13) = 62.05, multiple R2 = 0.93, p < 0.05). The pellets produced from fresh mature wood sawdust were found to be more prone to self-heating and off-gassing while steam drying the sawdust at high temperature and pressure led to a significant reduction in heat and gas generation across all materials. The heightened self-heating and off-gassing in mature wood pellet can be attributed to a higher proportion of sapwood in the raw material. The probable explanations to the observed differences are in line with biological mechanisms for self-heating and off-gassing, as well as the chemical oxidation of fatty and resin acids.