Effect Of Initial Moisture Content Research Articles

The effect of initial moisture content on water transport in concrete containing a hydrophobic admixture

The effect of initial moisture content on water transport in concrete containing a hydrophobic admixture

EFFECT OF INITIAL MOISTURE CONTENT ON THE THIN LAYER DRYING CHARACTERISTICS OF HAZELNUTS DURING ROASTING

ABSTRACT Effect of initial moisture content on the thin layer drying characteristics of hazelnuts during roasting was described for a temperature range of 100-160°C, using several thin layer equations. The effective diffusivity varied from 2.8×10−7 to 21.5×10−7m2/s over the temperature and moisture range. Temperature dependence of the diffusivity coefficient was described by Arrhenius-type relationship. The activation energy for moisture diffusion was found to be 2703 kJ/kg, 2289 kJ/kg and 2030 kJ/kg for the initial moisture content of 12.3% db, 6.14% db, and 2.41% db, respectively. Two-term equation gave better predictions than Henderson and Pabis and Thompson equations, and satisfactorily described thin layer drying characteristics of hazelnut roasting. A generalised mathematical model with the linear temperature dependence for moistured, non-treated and pre-dried hazelnuts were also developed.

Pecan Kernel Breakage and Oil Extracted by Supercritical CO2 as Affected by Moisture Content

ABSTRACTDuring supercritical CO2 extraction of oil from pecans, kernel breakage frequently occurs when the depressurization time is short. The purpose of this study was to investigate the effects of initial moisture content of pecan kernels and moisture equilibration time on pecan breakage and oil recovery when extracting with supercritical CO2. Initial pecan moisture content, adjusted to 3.5% to 11.0%, had a significant effect on breakage when using a short depressurization time. With higher pecan moisture, less kernel breakage occurred. Increasing moisture equilibration time from 1 to 48 h reduced kernel breakage and produced an average of 30% more oil during extraction. Moisture content did not significantly affect the amount of oil extracted.

Selected Properties of Laboratory-Made Laminated-Bamboo Lumber

An exploratory study was conducted to evaluate the properties of laminated-bamboo lumber, herein referred to as LBL. Quasi-flattened Moso bamboo (Phyllostachys pubescens) were laminated using a resorcinol-based adhesive to form a composite which is similar in construction to that of laminated-veneer lumber (LVL). Representative samples were tested for static bending properties, internal bond strength, and dimensional stability. The effect of initial moisture content (10 and 15 percent) and glue spread rate (220, 320 and 420 g/m 2 single glueline) on LBL properties was also analyzed. Results indicate that LBL exhibits superior strength property compared to wood-based LVL, as indicated by its higher MOR. Its MOE, however, was slightly lower. Initial MC (within 15 percent) did not have a significant effect on the mechanical properties of LBL, but it appears to have a significant effect on dimensional stability. Glue spread rate had a significant effect on both the mechanical and physical properties.

Moisture Effect on Compaction and Permeability in Composts

The effects of initial moisture content and compressive loads on the compactability and air permeability of two compost mixes, biosolids (primary) + bark + sawdust + recycled compost, and cow manure are described. Biosolids compost in the moisture range of 42–57% was subjected to compressive stresses of 0–43.2 kPa and the degree of compaction and pressure drops in the flow range of 0.05–0.20 m/s were measured. The relationship between air permeability and total air-filled porosity at different moisture levels was described using the Kozeny-Carman flow model. Biosolids showed significant compressive behavior and lower permeabilities with increasing moisture content (42–57%). Cow manure had a high moisture-retaining capacity and the differences in compaction behavior and air permeabilities were small when moisture levels were varied (57–73%). The model described the relationship between air permeability and effective free air space with a high level of accuracy (R2> 0.95) at all moisture levels and compacte...

Banana waste as substrate for α-amylase production by Bacillus subtilis (CBTK 106) under solid-state fermentation

Bacillus subtilis CBTK 106, isolated from banana wastes, produced high titres of α-amylase when banana fruit stalk was used as substrate in a solid-state fermentation system. The effects of initial moisture content, particle size, cooking time and temperature, pH, incubation temperature, additional nutrients, inoculum size and incubation period on the production of α-amylase were characterised. A maximum yield of 5 345 000 U mg-1 min-1 was recorded when pretreated banana fruit stalk (autoclaved at 121 °C for 60 min) was used as substrate with 70% initial moisture content, 400 μm particle size, an initial pH of 7.0, a temperature of 35 °C, and additional nutrients (ammonium sulphate/sodium nitrate at 1.0%, beef extract/peptone at 0.5%, glucose/sucrose/starch/maltose at 0.1% and potassium chloride/sodium chloride at 1.0%) in the medium, with an inoculum-to-substrate ratio of 10% (v/w) for 24 h. The enzyme yield was 2.65-fold higher with banana fruit stalk medium compared to wheat bran.

Evaluation of Soybean Seedcoat Cracking During Drying:PART I. Using Drying Tests

ABSTRACT In this study, seedcoat cracking during heated air drying was investigated in five varieties of Minnesota grown soybeans. Effects of initial moisture contents, drying temperatures and time on cracking levels were evaluated. Digital image analysis (DIA) was employed to measure initial sizes and shapes of soybeans in order to evaluate the influence of physical properties of mature seeds on cracking frequency. Seedcoat cracking rates increased significantly with increase in initial moisture content of the soybeans. drying temperature and time. Rapid water loss at higher initial moisture contents led to greater seedcoat cracking. Variety.growing location. and sizc of soybeans had significant influence on seedcoat cracking. Statistical analysis indicates that interactions between various factors had significant influence on seedcoat cracking.

Interactions between soil properties and moisture content in crust formation, runoff and interrill erosion from tilled loess soils

Soil-surface seals and crusts resulting from aggregate breakdown reduce the soil infiltration rate and may induce erosion by increasing runoff. The cultivated loess areas of northwestern Europe are particularly prone to these processes. Surface samples of ten tilled silty loamy loess soils, ranging in clay content from 120 to 350 g kg −1 and in organic carbon from 10 to 20 g kg −1, were packed into 0.5 m 2 plots with 5% slopes and subjected to simulated rainfall applied at 30 mm h −1. The 120 minutes rainfall events were applied to initially field-moist soil, air-dried soil and rewetted soil to investigate the effect of soil moisture content prior to rainfall. Runoff and eroded sediments were collected at 5 minutes intervals. Aggregate stability of the soils was assessed by measuring particle-size distribution after different treatments. All soils formed seals. Runoff rates were between 70 and 90% by the end of the rainfall event for field-moist plots. There were large differences between soil runoff rates for the air-dried and rewetted plots. Interrill erosion was associated with runoff, and sediment concentration in runoff readily reached a steady-state value. Measurements of aggregate stability for various treatments were in good agreement with sealing, runoff and erosion responses to rainfall. Runoff and erosion were lower for air-dried plots than for field-moist plots, and were either intermediate or lowest for rewetted plots, depending on soil characteristics. Soils with a high clay content had the lowest erosion rate when they were rewetted, whereas the soil with a high organic-carbon content had the lowest erosion rate in air-dry conditions. The results indicate the complexity of the effect of initial moisture content, and the interactions between soil properties and climate.

Time‐dependency of runoff velocity and erosion the effect of the initial soil moisture profile

AbstractThe paper reports on experiments carried out to evaluate the effect of the initial soil moisture profile on temporal variations in runoff erosion rate. The moisture profile was varied by applying infrared heating to the soil sample surface over various time periods, while runoff erosivity was varied by varying the slope of the flume. The experiment confirms that dry loamy soils are very erodible: on a slope length of only 4.3 m long sediment concentrations are near transporting capacity in case of a dry soil sample. It appears that temporal variations in sediment concentrations can be well simulated using a simple relationship between runoff erosion resistance and initial soil moisture content, thereby implicitly assuming that the effect of initial moisture content is persistent over the whole duration of the experiment. The implications of these findings with respect to the modelling of sediment output from larger catchments and the design of experiments on rill erodibility are discussed.The experiments also show that, under the present circumstances, mean velocities in the rills appear to be independent of slope. This finding may be of importance with respect to overland flow routing and deterministic erosion modelling.

Lime stabilisation of glacial clay : Barnes, G E; Reynolds, W S Highways TranspV36, N6, June 1989, P26–32

Although lime stabilisation has been adopted in road building in Europe and the USA, only recently has it been used in the UK for capping layers. The paper examines the effect of lime stabilisation on the density, unconfined compression strength, moisture condition value, and modulus of a gravelly clay (glacial clay). A project to investigate the effects of initial moisture content, gravel content, lime content and compaction energy on the unconfined compressive strength is described. Moisture condition value and Proctor compaction tests were carried on a number of lime stabilised mixes. Results show that the strengths achieved are likely to make lime stabilisation suitable only for subgrade improvement of glacial clays, particularly those of law plasticity. Density is not a good measure of performance as it is affected by variable properties of the soil such as plasticity, moisture content and stone content. Strength is controlled by the initial moisture content, with an optimum for maximum strength. For wetter soils the strength is not increased significantly with increasing lime content, but for drier soils the stabilised matrix is more brittle with a moderate amount of gravel producing a weak, honeycombed structure. Glacial clays are sensitive to moisture content change because of their low plasticity and variable stone content.

Unsaturated water transmission characteristics of soils in relation to texture, aggregate size and initial moisture content

SummaryTo study the effect of soil texture, aggregate size and initial moisture content on soil water diffusivity, D(θ), and unsaturated hydraulic conductivity, K(θ), horizontal absorption experiments were conducted on samples of loamy sand, sandy loam and clay–loam soils as well as on artificially prepared water-stable aggregates of a clay–loam sample (sizes 0.·25–0–25, 0·25–0·5, 0·5–1, 1–2, and 2–4 mm). For comparable moisture contents, D(θ) followed the order loamy sand > sandy loam > clay–loam. The effect of initial moisture content on D(θ) varied with soil texture. K(θ), which was evaluated using D(θ) for air-dry initial moisture content and the slopes of the water retention curves, also varied with soil texture.The D(θ) function for air-dry initial moisture content increased with the decrease in aggregate size, the increase being more pronounced below a size of 1 mm. Values of D(θ) obtained from initially airdry soil and at 10% of saturation moisture content did not differ greatly from one another. The K(θ) function was almost the same for aggregate sizes 1–2 and 2–4 mm. In the size ranges of < 1 mm, K(θ) increased with the decrease in aggregate size. The particle/aggregate size range of 0·1–0·5 mm was the most conducive to unsaturated water flow.

The effect of initial moisture content and rain (sprinkler) intensity on wetting front advance during rain (sprinkler) infiltration

A laboratory experiment was carried out on a 5 cm inside diameter by 70 cm long column of silty clay soil under five initial moisture contents, and five sprinkler intensities using a sprinkler simulator. A general equation was derived taking into account the initial moisture content and water application rate, to compute the wetting front advance during sprinkler infiltration. The experimental results strongly supported the derived equation, and the wetting front advance could be predicted under any combination of initial moisture content and sprinkler intensity. The study also revealed that the advance of wetting front increases either by increasing the sprinkler intensity or initial moisture content. The numerical solution of the partial differential equation of water flow offered by HANKS et al. (1969) was applied to compute the wetting front advance during the sprinkler infiltration. A good agreement was found between the two methods of computations; the derived equation and the differential equation. However, the solution of the partial differential equation needs very accurate estimation of K − Θ and ψ − Θ relation-ships to achieve reliable results.

Effects of initial moisture content and light intensity on the photo-degradation of aflatoxin B 1 in contaminated rice

Contaminated milled rice containing 1100 μg aflatoxin B1 per kg was adjusted to various initial moisture contents (14—24%), then exposed to light intensities of 43 mW/cm2 and 64 mW/cm2 at 36 °C and 42 °C respectively for different periods up to 24 h. The results indicate that all treatments caused a decrease of aflatoxin B1. However, at 43 mW/cm2 and 36 °C, increase in sample initial moisture content led to a reduction in the amounts of aflatoxin recovered, with mean values of 413, 352 and 351 μg toxin/kg rice at 14·1, 18·7 and 24·4% initial moisture content respectively. At 64 mW/cm2 and 42 °C, increase in sample initial moisture content led to an increase in the amounts of toxin recovered, with mean values of 238, 276 and 286 μg toxin/ kg rice at 14·1, 18·7 and 24·4% initial moisture content respectively. High light intensity appears to cause rapid moisture loss and therefore reduced rate of toxin degradation. Visual examination of samples suggested that the varying degree of particle agglomeration resulting from the method of direct water addition may contribute to the increased aflatoxin recovery at higher initial moisture contents, due to limited penetration of light.

Effects of Initial Moisture Content and Storage Relative Humidity on Textural Changes of Layer Cakes During Storage

ABSTRACTA study was undertaken to examine the effects of initial moisture content and storage relative humidity on certain textural changes occurring in layer cakes during a 42‐day storage period at 20°C. Water activity and moisture determinations were carried out. Force compression curves from the Instron Universal Testing Machine allowed the estimations of cake firmness, adhesiveness, cohesiveness, and elasticity. Results indicated that increased cake moisture contents led to a decrease in initial cake firmness but did not reduce final cake firmness. Cakes stored at increased relative humidities lost a negligible amount of moisture but continued to increase in firmness and adhesiveness throughout the entire 42‐day period.

Steam pretreatment of lignocellulosic material for enhanced enzymatic hydrolysis

Pretreatment methods were compared with steam explosion, and differing views on the relative importance of mechanical and chemical effects were outlined. Hydrolysis was desirable; pyrolysis was undesirable. The effects of initial moisture content on steam consumption, mechanism and rate of heat transfer, pentosan solubilization, and subsequent glucose yield were summarized. The insignificant effect, after treatment at 240 degrees C, of 90% pressure bleed-down before explosion on subsequent simultaneous saccharification and fermentation (SSF) yields was described. Treatment at 190 degrees C with complete bleed-down (no explosion), when compared with that at 240 degrees C with explosion from full pressure, showed at least as good solubilizatoin of pentosan, enzymatic hydrolysis, and SSF but showed greater pentosan destruction for the same degree of pentosan removal. Water washing of unexploded steamed aspenwood chips was at least as efficient as that of similarly treated but exploded chips. Scanning electron micrographs of unexploded chips showed extensive rupturing of vessel pit membranes and other morphological features associated with steam-exploded wood. Neither the explosion nor the high temperatures (above 190 degrees C) are necessary.

Effect of Initial Moisture Content on Infiltration in an Orissa Soil

Effect of initial moisture content on Kostiakov-Lewis type infiltration equation was studied in a soil in Orissa. The relationship between constant K. exponent, n and initial moisture content, X has been shown in a form of graph. A methematical relation- ship between accumulated depth of infiltration for the period of 30 minutes and moisture content has been developed.

The effect of initial moisture content and infiltration quantity on redistribution of soil water

The effects of initial moisture content and infiltration quantity on redistribution of water were studied in a loam, a fine sand, and a coarse sand. Moisture profiles during redistribution were obtained by gamma ray attenuation. Measured values of the hydraulic properties of these soils were used to calculate fluxes at the transition from drainage to wetting. The results were used to check a recent analysis of Peck. Gravity effects dominated in both sands, while in the loam capillary effects dominated at the smaller initial moisture contents and infiltration quantities. In all materials, increasing initial moisture content or infiltration quantity increased the contribution of gravity to the flux at the transition, and decreased the contribution due to capillary potential gradients. For a particular material, it depends on the magnitude of these fluxes whether mean moisture contents in the draining zone will be higher or lower at increasing values of initial moisture content or infiltration quantity.

Infiltration and structural changes as influenced by initial moisture content

The variation of infiltration behaviour, in columns of aggregates of a structurally stable and an unstable soil, caused by pre-equilibrating the aggregates with a range of relative humidities from 0 to 98%, was measured in terms of advance of the front, cumulative infiltration, slaking, and swelling. In this range, the effect of initial moisture condition on the stable soil (krasnozem) was slight compared with that on the unstable soil (black earth); the wetter the soil initially, the greater was the infiltration rate, and the smaller the slaking and swelling. The change in the behaviour of infiltration into systems of stable aggregates is reflected as (1) an increase in the importance of the sorptivity, and (2) a reduction in the importance of the hydraulic conductivity contribution to the steady-state infiltration process. (The aggregates of 1/2-1 mm are of such a size that the sorptivity contribution should not normally be detectable in stable soils.) It is suggested that in the unstable soil, the heat of wetting is associated with aggregate collapse. The degraded structure of the surface layers prevents fast entry of water into the lower layers. The collapse of structure dominates the infiltration process so that the analysis in terms of sorptivity carried out for stable aggregates cannot be made. The effect of entrapped air on slaking of aggregates of these soils is shown to be negligible compared with the effect of initial moisture content. The application of the results to flood irrigation of unstable soils under field conditions is briefly considered.

Mechanical Tests of Cellulose Acetate—III

Abstract Data are presented from additional mechanical tests of specimens taken from the same sheet of cellulose acetate for which tests have been reported in two previous papers by the author. The tests were conducted in a laboratory maintained at a constant temperature of 77 F and a relative humidity of 50 per cent: (1) Repeated bending (fatigue) tests were made at different speeds of testing and different ranges of stress, which demonstrate that both of these variables are important. The effect of different shapes of fatigue specimens (circular, square, and rectangular cross sections) on the endurance limit is also discussed. (2) Static compression tests of preconditioned specimens tested at intervals of time up to 10 months show the effect of initial moisture content and time on the yield point and the weight. (3) Static torsion, tension, and compression tests, conducted at the same rate of strain, indicate the effect of rate of strain and type of loading on the strength properties of the material. (4) Static tension tests of a specimen containing a transverse hole show the effect of a stress concentration on the tensile strength.