Effect Of Initial Water Content Research Articles

Effect of initial water content and curing moisture conditions on the development of fly ash-based geopolymers in heat and ambient temperature

It has been claimed that water has no role to play in the formation of hardened geopolymer paste apart from providing the workability and necessary reaction medium. It has further been generally accepted that heat treatment is necessary for producing fly ash geopolymer concrete. This is considered a drawback affecting its manufacture and feasibility. The research presented in this paper was conducted in the aim of improving the ambient-cured (20°C) geopolymer. This has been achieved by controlling the moisture condition of the specimens after hardening. This paper also examines whether there are mechanical effects as a result of variation in the initial water content. It further explores whether a combination of such variation together with controlling the curing regime may lead to desired improvement in the mechanical properties. The role of water was studied by monitoring the microstructural and mineralogical developments and relating them to the gain in strength. It has been found that reducing water content in the initial state and controlling the moisture condition during a curing period after hardening are beneficial and lead to extra strength gain in the ambient-cured fly ash-based geopolymer. This helps the ambient-cured geopolymer achieve strength levels comparable to those of heat treatment within a relatively short curing period.

Inversion of Surface Nuclear Magnetic Resonance by Regularization with Simulated Atomic Transition Method

Initial water content impacts the accuracy and resolution of the inversion in surface nuclear magnetic resonance (SNMR). In order to solve this problem, a new method called as regularization combined with simulated atomic transition method (RSATA) is proposed. The inversion of SNMR is transformed into an unconstrained nonlinear global optimization problem, and it solved directly by RSATA without pre-assigning the initial water content distribution. The conjugate gradient linear iterative algorithm is adopted to look for local minimum and global extreme value when using RSATA, and has improved the inversion speed. Results show that this method is a very good solution to solve the effect of initial water content and it is also better than the existing methods on the operation efficiency and the accuracy of inversion.

Effect of initial water content on undrained shear behaviour of reconstituted clays

Isotropically consolidated undrained triaxial compression shear tests were performed on three reconstituted clays to investigate the effect of initial water content w0on undrained strength behaviour. The values of w0were adjusted within the range of 1·0–2·0 times the liquid limit. The predominant clay mineral is identified as illite for the considered clays, based on a semi-quantitative analysis of the X-ray diffraction patterns. The laboratory tests show that the stress–strain curve in terms of deviator stress against axial strain and the effective stress path in terms of deviator stress against effective mean stress are significantly affected by w0. The undrained strength ratio R*su, defined as the ratio of the undrained shear strength S*uto the isotropic consolidation stress, varies with w0within a wide spectrum, ranging from 0·28 to 0·60 for the three reconstituted clays investigated. The relationship between void index Ivand S*uchanges with R*su, and becomes identical to the intrinsic strength line proposed by Chandler when R*su= 0·33. It is also evidenced from the laboratory tests that the value of S*udepends on both the water content and the liquid limit.

Kinetic Model with Effect of Water Content for Enzyme-Catalyzed Citronellyl Laurate Esterification Process

A kinetic model with effect of water content for enzyme-catalyzed citronellyl laurate was developed. These models incorporate the combined influences of established kinetics model with the function model on the effect of initial water content with kinetic parameters. The model development was carried out by performing a linear and nonlinear regression based on the behavior of the kinetic parameter profiles and validated with experimental data. Using the developed models, the influence of water content towards the enzyme-catalyzed initial rate of reaction was theoretically explained. It has been shown that the proposed model have good agreement between experimental data and intends to capture the effect of water content towards the conversion of ester. With this model, the optimal value of initial water content for this process could be estimated.

Intrinsic Compression Behavior of Remolded and Reconstituted Clays-Reappraisal

Evaluating the impacts of soil structure on mechanical behavior for natural sedimentary clays is an important issue in geotechnical engineering. Burland introduced void index for normalizing the compression curves of various remolded and reconstituted clays to obtain the intrinsic compression line, which provides a reference framework to assess the in-situ compression behavior. However, it does not quantitatively account for the effects of initial water content on compressive behavior of remolded and reconstituted clays and the initial water contents of clays are not always limited to 1.0 - 1.5 times the liquid limits defined by Burland. A modification based on collected tests data was presented on the expressions of and defined by Burland. Extensive oedometer test data were also collected on various remolded and reconstituted soils with distinct liquid limits and initial water contents to verify the validity of modified expressions. A normalized compression line deduced by intrinsic compression line is proposed in the e-log p plot, which can be used to evaluate the effects of soil structure quantitatively on the intact compressive behavior for natural sedimentary clays.

The Experimental Study of the Effect of Initial Water Content on Water Transport and Distribution Characteristics in Injection Irrigation

The effect of initial water content on water transport characteristics in injection irrigation is analyzed through an indoor experiment of injection irrigation in different initial water contents. The research shows the following results. The relationship between the cumulative infiltration and time accords with power function. The higher the initial water content is, the bigger the cumulative infiltration is in the same time. The wetting front is a semi-circle with its center below the water outlet, the transport velocity of which slows down with the passing of time. The transport velocity of vertical section crossing the middle of the two outlets approaches that of vertical section at the middle point of the central line of the two outlets. The higher the initial water content is, the shorter the time of the transport velocity of the two sections similar to each other is. The water wetted range is comparatively wider, and the water content is comparatively higher below the outlet, and it is reverse above the outlet. The higher the initial water content is, the wider the wetted range is and the higher the water content of the soil being the same distance from the outlet is. The above research provides a basis for supplementing the theories and technologies of injection irrigation.

Advance of Wetting Front in Silt Loam Soil under a Trickle Line Source

Under drip irrigation , the plant's root is concentrated inside the wetted bulb (region). Thus, the development of these roots and the plant production are greatly affected by the wetting pattern. Therefore, the wetting pattern of soil under drip irrigation must be taken into consideration in the design of drip irrigation system for both single dripping source or multi-overlapping wetting patterns of dripping water sources.The aim of this study is to evaluate the effect of initial water content of the soil and spacing between two adjacent dripping sources with different flow rate on the movement of the wetting front.This study included 16 tests for monitoring the advancement of the wetting front with time during and after the water application phase. The water advance and water distribution measurement are carried out for two cases of the soil profile: for the first case with initial volumetric water content of 4.08% and for the second case with initial volumetric water content of 12.24%. Two spacing between the emitter were tested 25cm and 50 cm using application flow rates of 0.606, 1.212, 1.818, and 2.424 cm3 /min/cm to show the combined effect of spacing and flow rate on the performance of two adjacent emitter.The study proposed a method for determining the spacing between the two emitting sources , the water application rate and watering time. The proposed method depends on a wetted zone whose depth is equal to the root zone depth with a values equals to the maximum vertical advance of the wetting front underneath the drip line at time when this depth is equal to the depth of wetting at midpoint between the drip line. the study revealed that both the vertical water advance in soil underneath the emitter and the horizontal advance of the wetting front is larger than those in the case of single emitter.Furthermore, the vertical water advance increases with the decrease spacing between the two drip lines. Also, the horizontal advance of the wetting front is not affected by varying this spacing for both studied cases of initial water content.

Effects of the maximum soil aggregates size and cyclic wetting–drying on the stiffness of a lime-treated clayey soil

Lime treatment is a well-known technique to improve the mechanical response of clayey subgrades of road pavements or clayey soils used for embankment. Several studies show that lime treatment significantly modifies the physical and hydromechanical properties of compacted soils. Nevertheless, studies on the scale effect under climatic changes are scarce. Actually, wetting–drying cycles might significantly modify the microstructure of treated soils, giving rise to changes in hydromechanical properties. This modification could be dependent on the size of soil aggregates before lime treatment. In the present work, this scale effect was studied by investigating the stiffness of a compacted lime-treated clayey soil using bender elements. The studied soil was first air-dried and ground into a target maximum soil aggregates size (Dmax). For each aggregate size, the soil was humidified to reach the target water contents wi, then mixed with 3% of lime powder (mass of lime divided by mass of dried soil) prior to the static compaction at a dry density of 1·60 Mg/m3. Two initial water contents (wi = 14 and 18%) and four maximum soil aggregates sizes (Dmax = 0·4, 1·0, 2·0 and 5·0 mm) were considered. After the compaction, the soil specimen (50 mm in diameter and 50 mm high) was covered by plastic film in order to prevent soil moisture changes. The soil stiffness was then monitored at variable time intervals until reaching stabilisation. Afterwards, the soil specimen was subjected to full saturation followed by air-drying to come back to its initial water content. The results show that: (a) the soil stiffness after lime-treatment is significantly dependent on the aggregate size: the finer the aggregates the higher the soil stiffness; (b) the effect of initial water content on the stiffness is negligible; and (c) the wetting–drying cycles seem to slightly increase the soil stiffness in the case of lime-treated specimens and decrease the soil stiffness in the case of untreated specimens. Furthermore, when an intensive drying was applied reducing the soil water content lower than the initial level, the soil stiffness decreased drastically after the subsequent wetting.

Effect of initial water content on saturated hydraulic conductivity in desalinization with slaking and drying

Soil slaking is an environment-friendly technique that is gaining importance in restoring saline soils. The objective of this article is to evaluate the effect of initial water content (IWC) on saturated hydraulic conductivity (Ks) in desalinization with slaking and drying. Accordingly, a slaking test was carried out during February, 2009 for evaluating the effects of slaking and drying on Ks, sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP) under various IWC. We prepared natural and air-dried soils of paddy field in Kojima Bay Polder, Japan to give different pre-drying, air-dried, and not dried (natural). The air-dried soils were resaturated. Each soil was well mixed, then dried to different initial moisture contents (60, 50, 40, 30, 20, and 10% by weight). The specimens were immersed into water in the pot for 24 h. The Ks was measured, and cations in slaked and unslaked soils were analyzed. The Ks was high under the water content below 30% in both the natural and the air-dried soils. But the effects were more pronounced in the natural soil. The air-dried soil showed far smaller Ks than the natural soil. In outer solution, the highest SAR was noted at 30% in the natural and 30 and 20% in the air-dried soils. Significant decrease in ESP of the soils (slaked + unslaked) was also observed at the same water content. Lower water content was more effective in decreasing the soil ESP after desalinization from saline soil. The natural soil showed lower ESP and higher porosity, which was considered as a reason for higher Ks of natural soil than that of air-dried soils. The results indicated that lower water content (10–30%) had no hazardous effect on Ks by slaking and drying of soil.

Effects of initial water content on steam reforming of aliphatic hydrocarbons with nonthermal plasma

The effects of initial water content on steam reforming of aliphatic hydrocarbons such as methane, propane, and neopentane with nonthermal plasma were analyzed in terms of substrate conversion, carbon recovery, and product selectivity. It was found that water addition increased CO 2 yield despite a decrease in substrate conversion. The number of carbon atoms in the substrate hydrocarbon affected the additive effect due to the insufficient supply of oxygen atoms from water. Plausible reaction pathways for the conversion of substrate to CO x are proposed to explain the relative concentrations of CO x species; these pathways involved different precursors for CO and CO 2.

Effects of water content in an ethanol-based solvent on sol-gel synthesis of Zn2SiO4:Mn phosphors

The effects of initial water content in an ethanol-based solvent during a sol-gel synthesis of Zn2SiO4:Mn green-emitting phosphor were studied. The emission intensity and the decay time of the Zn2-xMnxSiO4 phosphor were measured according to the different initial water contents in two different precursor combinations. The single-phase formation of the host lattice, the suppression of the residual second phase, emission efficiency, and decay time were studied by changing the initial water content in the ethanol-based solvent during solgel synthesis of the Zn2-xMnxSiO4 phosphors.

Experimental Study on the Cyclic Resistance of a Natural Loess from Northern France

In order to analyze the instability phenomenon observed along the Northern High Speed Line of R\'eseau Ferr\'e de France (RFF), soil blocks were taken at a site near the railway, at four different depths (1.2, 2.2, 3.5 and 4.9 m). Cyclic triaxial tests were carried out on saturated and unsaturated soil specimens. The results from tests on initially saturated specimens showed that the soil taken at 2.2 m depth has the lowest resistance to cyclic loading, in relation to its highest porosity and lowest clay fraction. This soil was then studied at unsaturated state with various initial water contents. Unsaturated soil specimens were first subjected to cyclic loadings to decrease their volume. These cyclic loadings was stopped when the volume decrease was approximately equal to the initial pore air volume, or when the pores filled by air were eliminated and the soil was considered to become saturated. Afterwards, the back-pressure tubing was saturated with de-aired water and cycles were applied under undrained condition. Significant effect of initial water content was evidenced: the lower the initial water content, the higher the cyclic resistance. This can be explained by the densification of the soil during the initial cyclic loadings.

Drying Characteristics of Fine Powders in an Inert Medium Circulating Fluidized Bed

The effects of inlet gas velocity (1.53–1.75 m/s), inlet gas temperature (50–80°C), mass ratio between fine powder and inert particle (F/I ratio, 0.05–0.2) and initial water content (8.5–31.6 wt%, wet basis) on the drying rate were determined in an inert medium circulating fluidized bed (0.085 m ID × 1.0 m high). Glass beads (dp = 327.5 μm, ρs = 2,500 kg/m3) as inert particles and poly methyl methacrylate (PMMA) beads (dp = 12.5 μm, rs = 1,190 kg/m3) as fine powders were used. The drying rate increases with increasing inlet gas temperature, gas velocity and the F/I ratio. The effect of initial water content on the drying rate was negligible compared with the other variables. The obtained drying rate data have been correlated with inlet gas temperature, gas velocity, F/I ratio, and the initial water content.

A review of non‐equilibrium water flow and solute transport in soil macropores: principles, controlling factors and consequences for water quality

SummaryThis review discusses the causes and consequences of ‘non‐equilibrium’ water flow and solute transport in large structural pores or macropores (root and earthworm channels, fissures and interaggregate voids). The experimental evidence suggests that pores larger thanc. 0.3 mm in equivalent cylindrical diameter allow rapid non‐equilibrium flow. Apart from their large size and continuity, this is also due to the presence of impermeable linings and coatings that restrict lateral mass exchange. Macropores also represent microsites in soil that are more biologically active, and often more chemically reactive than the bulk soil. However, sorption retardation during transport through such pores is weaker than in the bulk soil, due to their small surface areas and significant kinetic effects, especially in larger macropores. The potential for non‐equilibrium water flow and solute transport at any site depends on the nature of the macropore network, which is determined by the factors of structure formation and degradation, including the abundance and activity of soil biota such as earthworms, soil properties (e.g. clay content), site factors (e.g. slope position, drying intensity, vegetation) and management (e.g. cropping, tillage, traffic). A conceptual model is proposed that summarizes these effects of site factors on the inherent potential for non‐equilibrium water flow and solute transport in macropores. Initial and boundary conditions determine the extent to which this potential is realized. High rain intensities clearly increase the strength of non‐equilibrium flow in macropores, but the effects of initial water content seem complex, due to the confounding effects of soil shrinkage and water repellency. The impacts of macropore flow on water quality are most significant for relatively immobile solutes that are foreign to the soil and whose effects on ecosystem and human health are pronounced even at small leached fractions (e.g. pesticides). The review concludes with a discussion of topics where process understanding is still lacking, and also suggests some potential applications of the considerable knowledge that has accumulated in recent decades.

Tannase production by solid state fermentation of cashew apple bagasse

The ability of Aspergillus oryzae for the production of tannase by solid state fermentation was investigated using cashew apple bagasse (CAB) as substrate. The effect of initial water content was studied and maximum enzyme production was obtained when 60 mL of water was added to 100.0 g of CAB. The fungal strain was able to grow on CAB without any supplementation but a low enzyme activity was obtained, 0.576 U/g of dry substrate (g(ds)). Optimization of process parameters such as supplementation with tannic acid, phosphorous, and different organic and inorganic nitrogen sources was studied. The addition of tannic acid affected the enzyme production and maximum tannase activity (2.40 U/g(ds)) was obtained with 2.5% (w/w) supplementation. Supplementation with ammonium nitrate, peptone, and yeast extract exerted no influence on tannase production. Ammonium sulphate improved the enzyme production in 3.75-fold compared with control. Based on the experimental results, CAB is a promising substrate for solid state fermentation, enabling A. oryzae growth and the production of tannase, with a maximum activity of 3.42 U/g(ds) and enzyme productivity of 128.5x10(-3) U x g(ds)(-1) x h(-1).

Effect of solvent and initial water content on ( R, S)-1-phenylethanol resolution

The enzymatic resolution of ( R, S)-1-phenylethanol was carried out in various organic solvents. Two commercial immobilized lipases, such as ChiroCLEC-PC and Chirazyme L2, c.f., C3, lyo used in this study could exhibit the highest performance in isooctane. The effects of initial water content on the activity and enantioselectivity of the enzymes were also investigated. The method of direct contact pre-equilibrium, such as substrate pre-equilibrium and enzyme pre-equilibrium were used in this study. The resolution was favourable in the absence of additional water and water mimicking compound such as glycerol in the reaction system. The enantioselectivity of the enzymes was not affected by the organic solvents tested and the initial water content ranging from 0 to 0.5% (v/v). The enzymes were very selective toward the ( R)-1-phenylethanol with the enantioselectivity value more than 200.

Differential scanning calorimetry study of glass transition in frozen starch gels.

The effects of initial water content, maximum heating temperature, amylopectin crystallinity type, and annealing on the glass transition of starch gels were studied by differential scanning calorimetry (DSC). The glass transition temperatures of the frozen gels measured as the onset (T(g,onset)) or midpoint temperature (T(g,midpoint)), heat capacity change during the glass transition (deltaC(p)), unfrozen water of starch gels, and additional unfrozen water (AUW) arising from gelatinization were reported. The results show that T(g,onset) and T(g,midpoint) of the partially gelatinized gels are independent of the initial water content, while both of the T(g) values of the fully gelatinized gel increase as the initial water content increases. These observations might result from the difference in the level of structural disruption associated with different heating conditions, resulting in different gel structures as well as different concentrations of the sub-T(g) unfrozen matrix. The amylopectin crystallinity type does not greatly affect T(g,onset) and T(g,midpoint) of the gels. Annealing at a temperature near T(g,onset) increases both T(g,onset) and T(g,midpoint) of the gels, possibly due to an increase in the extent of the freeze concentration as evidenced by a decrease in AUW. Annealing results in an increase in the deltaC(p) value of the gels, presumably due to structural relaxation. A devitrification exotherm may be related to AUW. The annealing process decreases AUW, thus also decreasing the size of the exotherm.

Enzymatic synthesis of ethyl glucoside lactate in non-aqueous system

Ethyl glucoside lactate, a novel α-hydroxy acid derivative, was synthesized by transesterification in non-aqueous phase using immobilized lipase as biocatalyst. Parameters such as solvent type, substrate concentration, reaction temperature, and enzyme concentration were investigated to optimize the lipase-catalyzed transesterification. In solvent-free system with butyl lactate as both acyl donor and solvent, a 71% conversion was achieved. In order to investigate the effect of initial water content, the reactions were carried out in the mediums treated with molecular sieves. The results showed that conversion and initial rate decreased with the increase of water content. The conversion and initial rate reached to 95% and 67.4 mM/h, respectively, by carrying out the reaction under reduced pressure, which was employed to eliminate butanol and the initial water.

The effect of Initial Water Content on Maximum Frost Depth and Heat Balance —Studies on the analysis of freezing and thawing processes of soils (II)—

The effect of Initial Water Content on Maximum Frost Depth and Heat Balance —Studies on the analysis of freezing and thawing processes of soils (II)—

Mechanical behaviour of silty clay loam/peat mixtures: cyclic compression-release tests and effects of initial water content

Le comportement mecanique d'un limon argileux, seul ou en melange volumique avec 20 % ou 40 % de tourbe blonde est etudie pour differentes humidites initiales. Les materiaux sont soumis a 100 cycles de chargement-relâchement et des intensites de compression de 30 a 500 kPa. Une fonction simple permet de representer correctement la variation d'indice de vide sur les 80 derniers cycles et de proposer une valeur de tassement pour un nombre de cycles infini. L'ajout de 20 % et 40 % de tourbe ameliore l'indice de vide du limon compresse a 500 kPa de respectivement 55 % et 115 % pour les fortes humidites initiales. La comparaison du test a chargements repetes avec un test de compressibilite œdometrique donne des tassements similaires tant que les conditions sont non saturees. Pour tous les materiaux, la compression est importante pour un taux de saturation initial superieur a 0,5 et un indice de vide initial superieur a 0,9. L'utilisation d'un modele de melange permet de proposer des hypotheses d'interaction entre les composants en fonction de la teneur en eau initiale.