Air-dry Density Research Articles

The relations of fiber length, wood density, and compressive strength to ultrasonic wave velocity within stem of Melia azedarach

Radial and axial variations in the longitudinal ultrasonic wave velocity within stem of 17–19-year-old Melia azedarach planted in two different sites in northern Vietnam were experimentally investigated. Wood samples were collected from 10, 50, and 90% of the radial length from pith at 0.3, 1.3, 3.3, 5.3, and 7.3 m heights above the ground to measure ultrasonic velocity (Vu), fiber length (FL), air-dry density (AD), and compressive strength (CS) at moisture content approximately 12%. The average wave velocity for two sites exhibited minimum value near the pith about 3700 m/s. It kept increasing to 4200 m/s at the middle position before remaining constant value forward to outside. In axial direction, the variation of Vu with height was very small and without statistical significance. Vu had a strong positive linear relationship with both FL (r = 0.69, p < 0.001) and AD (r = 0.67, p < 0.001). These findings reveal that the FL and AD greatly influence the within-tree variations in the ultrasonic wave velocity in M. azedarach. Besides, the significant positive linear correlation between CS and Vu suggests that Vu was a useful predictor of the CS for M. azedarach planted in northern Vietnam.

Change of Bending Properties of 2×4 Larch Lumber According to Span Length in the Four Point Bending Test

This study was conducted to confirm an effect of span length on bending properties of larch dimensional lumber in the four point bending test. The size of specimen in this study was 38 (width) × 89 (depth) × 3,600 (length) mm3, and average air-dry density and moisture content of the specimens was 543.5 kg/m3 and 10.5%, respectively. Visually graded No. 1 dimensional lumbers of 248 were divided by two groups to compare modulus of rupture (MOR) and modulus of elasticity (MOE). One group was tested in the four point bending test with span length of 1,650 mm, and other was tested with span length of 3,000 mm. While MOE was not different according to span length in 5% significance level, MOR was different in accordance with span lengths and was in inverse proportion to change of span length. Fifth percentiles of MOR in span length of 1,650 and 3,000 mm were 28.65 and 25.70 MPa, respectively. It was confirmed that the difference between MORs in each case increased as normalized rank increased. This is because of size effect in Weibull weakest link failure theory. Therefore, KS F 2150, in which there is only regulation about span to depth ratio of 15 or more, is needed to be revised to contain a method considering size effect for MOR. From the method, various results of bending test with different size of lumber could be used to determine design value of lumber.

Utilization of dates palm kernel in high performance concrete

The utilization of agricultural dumps as ingredients in concrete has been studied by several researchers. One of which is the Palm Kernel Shells (PKS), which are a by-product in factories that produce date molasses (date honey). The aim of this study is to investigate the ability to produce high performance concrete by using Palm Kernel Shells (PKS), Crushed Palm Kernel (CPK) and Palm Kernel Ash (PKA) as replacement of concrete contents. The compressive strength, flexural strength, air dry density and absorption were tested in this investigation.The (PKS), (CPK) and (PKA) were replaced individually by weight of the course aggregate, fine aggregate and cement respectively using different percentages ranging from 5% to 20%. Also, they were mixed together in single mixes using different replacement percentages The physical and mechanical properties of each replacement were evaluated at 7, 28, and 56 days. Although the compressive strength has dropped around 28–40% for all replacement ratios, still, it remained within acceptable limits. On the other hand, the density was decreased considerably reaching a value of 1850 kg/m3 for mixture with (20%, 10%, 10%) (PKA), (CPK) and (PKS) replacement respectively and with compressive strength around 45 MPa at 28 days of age.

Wood properties of Larix sibirica naturally grown in Tosontsengel, Mongolia

ABSTRACTThe wood properties were examined for Larix sibirica naturally grown in Tosontsengel, Mongolia. The dynamic Young's modulus of the logs ranged from 6.31 to 9.65 GPa. The mean values of wood properties were as follows: water-extracted basic density = 0.44 g cm−3, air-dry density = 0.59 g cm−3, shrinkage at 1% moisture content change in the radial and tangential directions = 0.18% and 0.32%, modulus of elasticity = 11.24 GPa, modulus of rupture = 102.4 MPa, compressive strength parallel to the grain = 53.1 MPa, and mass loss by Fomitopsis palustris and Trametes versicolor = 10.4% and 18.6%. Mass loss in the heartwood was higher than that in the sapwood, indicating that the larger mass loss values in the heartwood of L. sibirica might be related to the larger amount of arabinogalactan.

Determining the predictive accuracy of whole tree modulus of elasticity (MOE) of 14-year-old loblolly pine using density and dynamic MOEs estimated by three different acoustic tools

Resonance based acoustic tools for evaluating wood properties have been reported to be more accurate in estimating the expected log MOE than time-of-flight (ToF) ones. However, there is no published study on the variations within different brands on these two major classes of acoustic tools. In this study, models were developed to predict the whole tree static MOE (WMOET) and rupture (WMORT) using log dynamic MOEs estimated by two resonance tools [Director HM200 (EHM200) and FAKOPP resonance log grader (ERLG)], ToF [FAKOPP Microsecond Timer (EFMT)], and density (green density, air-dry density) for a 14-year-old loblolly pine stand from two sites in the southern USA. The log velocity estimated by ToF was 33 and 30% more as compared to the resonance-based tools (Director HM200 and FAKOPP RLG respectively); translating into whole log static MOE (WMOEL) been 11 and 20% lower than those estimated by the resonance (HM200 and RLG respectively), and 90% lower than that estimated by the ToF tools (EFMT). Although the dynamic MOE estimated by ToF tool (EFMT) was higher, its WMOET predictive performance (R2 = 51%) lies between the 39 and 74% for the resonance based tools (HM200 and RGL respectively). This result supports the theory that ToF tools generate dilatational wave, and hence their velocity will be generally higher than resonance tools. The presence of predictive variation within the resonance suggests the need for within tools calibration. The linear relationship between the WMOET vs Etree was stronger than that of WMOET vs EHM200 suggesting that the ToF acoustic tool measurements are not restricted to the outer wood zone for small diameter logs.

Comparison of Whole-Tree Wood Property Maps for 13- and 22-Year-Old Loblolly Pine

Maps developed using Akima’s interpolation method were used to compare patterns of within-tree variation for Pinus taeda L. (loblolly pine) wood properties in plantation-grown trees aged 13 and 22 years. Air-dry density, microfibril angle (MFA) and modulus of elasticity (MOE) maps represented the average of 18 sampled trees in each age class. Near infrared (NIR) spectroscopy models calibrated using SilviScan provided data for the analysis. Zones of high density, low MFA and high MOE wood increased markedly in size in maps of the older trees. The proportion of wood meeting the visually graded No. 1 (11 GPa) and No. 2 (9.7 GPa) MOE design values for southern pine lumber increased from 44 to 74% and from 58 to 83% respectively demonstrating the impact of age on end-product quality. Air-dry density increased from pith to bark at all heights but lacked a significant trend vertically, while radial and longitudinal trends were observed for MFA and MOE. Changes were consistent with the asymptotic progression of properties associated with full maturity in older trees.

Some Physical and Mechanical Properties of Impregnated Chestnut Wood with Natural and Chemical Agent Exposed to Outdoor Conditions

Wood preservatives have been widely used to extend the service life of wood. The most objectionable environment for wood is outdoor conditions. In this study, test specimens prepared from chestnut wood (Castanea sativa Mill) were impregnated with natural and chemical impregnation agent. It was aimed to determine the effect of outdoor conditions on physical and mechanical properties of wood material by keeping them under these conditions for one year. As natural impregnation material pine tannin and acorn tannins, as chemical impregnation material imersol aqua and timbercare aqua were used. The retention amount, air-dried density, bending strength, modulus of elasticity, compression strength parallel to fibers, adhesion strength parallel to fibers, screw withdrawal strength were determined. As a result, it can be said that the physical and mechanical test values can compare wood impregnated with natural impregnation materials to wood impregnated with chemical impregnation materials after one year exposed to outdoor conditions.

Effect of cellular structure on the optical properties of wood

To construct robust calibrations of wood properties by near infrared spectroscopy, one must independently evaluate the spectral contributions of light absorption and light scattering. However, the light propagation in wooden cellular structures is difficult to interpret because these structures are complex, heterogeneous, and anisotropic. This study investigates the reduced scattering coefficients of softwood and hardwood (with ring-porous or diffuse-porous vessels) at 846 nm by time-resolved spectroscopy. It also evaluates the effect of wooden cellular structure and air-dry density on the light propagation. After determining the reduced scattering coefficients, we observed cross-sectional microscopic images of the wood samples. Eighty-five percent of the variation in the reduced scattering coefficients was explainable by the air-dry density, area ratio of the cell wall, and the median pore area. Monte Carlo simulations of the light propagation through wood revealed that most of the photon transport occurs in the cell-wall substance.

English

A comprehensive research has been carried out to understand the effect of adding carbon fibers to density and ultrasonic pulse velocity of self-compacting concrete. Fifteen SCC mixes were prepared with two types of mineral admixtures and carbon fibers. Metakaoline and silica fume were used as mineral admixtures while carbon fibers were used as fiber inclusions. Two different fiber length (6mm and12mm) and fiber fraction (0.1 % and 0.5 %) was used. Different parameters such as slump flow diameter, T500 time, V-funnel time, blocking ratio and filling height difference were used to evaluate fresh state properties. Air-dry density and Ultrasonic Pulse Velocity values are determined for mixes at age of 7, 28, 90 and 180 days. The experimental results indicate that concrete mixes contained carbon fiber showed higher air dry density than concrete mixes without fiber, the percentage increase were between 0.85% to 3.31% at age (7,28,90 and 180) days respectively. Concrete mixes contained carbon fiber compared with the reference mixes without carbon fiber exhibits an increase in the ultrasonic pulse velocity values of about 0.74% to 5% at age (7,28,90 and 180) days respectively .

Density and Ultrasonic Pulse Velocity Investigation of Self-Compacting Carbon Fiber- Reinforced Concrete

comprehensive research has been carried out to understand the effect of adding carbon fibers to density and ultrasonic pulse velocity of self-compacting concrete. Fifteen SCC mixes were prepared with two types of mineral admixtures and carbon fibers. Metakaoline and silica fume were used as mineral admixtures while carbon fibers were used as fiber inclusions. Two different fiber length (6mm and12mm) and fiber fraction (0.1 % and 0.5 %) was used. Different parameters such as slump flow diameter, T500 time, V-funnel time, blocking ratio and filling height difference were used to evaluate fresh state properties. Air-dry density and Ultrasonic Pulse Velocity values are determined for mixes at age of 7, 28, 90 and 180 days. The experimental results indicate that concrete mixes contained carbon fiber showed higher air dry density than concrete mixes without fiber, the percentage increase were between 0.85% to 3.31% at age (7,28,90 and 180) days respectively. Concrete mixes contained carbon fiber compared with the reference mixes without carbon fiber exhibits an increase in the ultrasonic pulse velocity values of about 0.74% to 5% at age (7,28,90 and 180) days respectively .

Analysis of temporal leachibility of trace elements to the environment of opoka-rocks used in historical building

The opoka-rock belongs to the silica-carbonate rocks commonly used in historical building. The research material in the form of rock fragments was taken from historical objects located in central Poland in Kazimierz Dolny on the Vistula river. In 8 time fractions according to NEN 7375: 2004 norm, the leachability of the main elements from the beryllium group considered as environmental indicators of building materials enriched with carbonate components was determined. After the application of the ICP sequential plasma-emission spectrometer according to the PN-EN ISO 11885 norm, the concentration of Ba, Mg, Sr, Zn, Mn was determined in the water eluates. In addition, physical and mechanical properties such as: open and total porosity, compressive strength in air-dry state, bulk density and specific density; were determined in accordance with the applicable standards. The results of the conducted research allowed finding that the number of leachabilities of the examined elements in decreasing succession were as follows: Mg &gt; Sr &gt; Zn &gt; Ba &gt; Mn. The highest leachability from the selected elements was found for Mg, which ranged from 0.22 to 1.14 ppm.

Microstructural characterization and evaluation of certain important physical properties of thuja burl wood

This investigation aimed to characterize certain important anatomical, chemical and physical properties of Tetraclinis articulate (Thuja) burl wood from Morocco. Anatomical properties and constituent structure were analysed using image analysis system, environmental scanning electron microscope (ESEM) and powder x-ray diffraction techniques. A few important physical properties of Thuja burl wood such as density, specific gravity, equilibrium moisture content (EMC), total swelling and water absorption characteristics were evaluated. Real-time water absorption and swelling profiles were recorded electronically using a digital force sensor and linear variable differential transformers (LVDTs) respectively. Microscopic structure observed on fractured surfaces showed very compact and thread-like fibers. Average crystallinity index and diameter of cellulose crystallite was found to be 0.35±0.03 and 36.00±5.58 A respectively. The average values of air-dry density and the EMC of Thuja burl wood were 932.67±50.57 kg/m3 and 10.19±1.43% respectively. Swelling profile as a function of the water immersion duration followed a curvilinear variation with maximum swelling coefficient of 2.9±0.43% after 24 hour from oven-dry condition. The suitability of this wood for decorative and handicraft items is attributed mainly to its dense microstructure, higher dimensional stability, lower water absorption, random grain texture, dark brownish with intense and pleasant smell.

Drying kinetics and determination of water sorption isotherms of corn

The study was carried out for the purpose of determining the drying kinetics as well as moisture sorption isotherm of hybrid-81 corn. Corn at about 31% moisture content (wb) was dried in a forced convective hot air cabinet dryer at different drying conditions, such as variable air dry bulb temperature (40°C, 50°C and 60°C) and loading density (3.56 kg/m2, 7.12 kg/m2, and 10.68 kg/m2) as well as in shining sun at different layers (3.56 kg/m2, 7.12 kg/m2, and 10.68 kg/m2). The water sorption isotherm of the dried corn was developed using vacuum desiccators, which contained saturated salt solutions in the range of 11-93% RHs. The mono-layer moisture content calculated by the Brunauer–Emmett–Teller (BET) model (6.76 g/100 g solid) was lesser than that calculated by the Guggenheim–Anderson–De Boer (GAB) model (10.53 g/100 g solid). The energy constants were 10.45 and 4.64 as per BET and GAB equation, respectively. Both models gave suitable fits for corn. The activation energy (Ea) for diffusion of water was found to be 11.09 kcal/gm-mole for corn. Furthermore, it was noticed that, with the increase of corn layer, the drying rate decreased in case of both sun and mechanical drying. However, higher loading density resulted in efficient drying, at least up to 10.7 kg/m2. It was shown that the drying time to obtain stability was the lowest for moisture content (12.08 %) corresponding to aw of 0.65 in case of BET or GAB monolayer moisture content. This finding could be helpful in predicting the storage life of corn.J. Bangladesh Agril. Univ. 15(2): 309-317, December 2017

Determination of Air-dry Density of Wood with Polychromatic X-ray and Digital Detector

Gravimetric method is usually used to evaluate air-dry density, which is governing physical or mechanical properties of wood. Although it had high evaluation accuracy, the method is time consuming process. Thus, this study was conducted to estimate air-dry density of wood with high accuracy by using polychromatic X-ray and digital detector as alternative of gravimetric method. To quantify polychromatic X-ray projection for evaluating air-dry density, Lambert-Beer’s law with the integral value of probability function was used. The integral value was used as weighting factor in the law, and it was determined by conducting simple test at various penetration depths and tube voltage. Mass attenuation coefficient (MAC) of wood also calculated by investigating polychromatic X-ray projection according to species, penetration depth and tube voltage. The species had not an effect on change of MAC. Finally, an air-dry density of wood was estimated by applying the integral value, MAC and Lambert-Beer’s law to polychromatic X-ray projection. As an example, the relation of the integral value (α) according to penetration depth (t, cm) at tube voltage of 35 kV was α=–0.00091t×0.0184 while the regression of the MAC (μ, cm2/g) was μ=0.5414exp(–0.0734t). When calculation of root mean squared error (RMSE) was performed to check the estimation accuracy, RMSE at 35, 45 and 55 kV was 0.010, 0.013 and 0.009 g/cm3, respectively. However, partial RMSE in relation to air-dry density was varied according to tube voltage. The partial RMSE below air-dry density of 0.41 g/cm3 was 0.008 g/cm3 when tube voltage of 35 kV was used. Meanwhile, the partial RMSE above air-dry density of 0.41 g/cm3 decreased as tube voltage increased. It was conclude that the accuracy of estimation with polychromatic X-ray and digital detector was quite high if the integral value and MAC of wood were determined precisely or a condition of examination was chosen properly. It was seemed that the estimation of air-dry density by using polychromatic X-ray system can supplant the gravimetric method.

Dynamic Simulations of the Cake Growth and the Uniformity for the Slip Casting Process

The computer simulation methods of cake growth properties were studied for the slip casting of alumina with gypsum mold. Based on the two-phase flow mixture model, mass conservation of water and maximum close-packed density theory, the numerical calculations were performed for the dynamical cake uniformity, cake density, mold thickness and effective applied pressure in this work. Good agreement was observed between the experimental experience and simulated cake uniformity with the different volume fractions of the slurry and the different sprue gate location conditions. The air-dried cake density and appropriate mold thickness can be estimated quickly by the present formulas. It is useful to simulate the dynamical cake properties with different process conditions which are difficult to detect.

Comparison of wood physical and mechanical traits between major gymnosperm and angiosperm tree species in China

Many wood physical and mechanical traits are important functional attributes for tree species, but variation in these traits among taxonomic categories such as between gymnosperms and angiosperms is still poorly documented. Here, the systematic differences in 12 traits and their allometric relationships between the two tree categories and the potential effects of phylogeny are explored based on a database for major gymnosperm and angiosperm tree species across China. The results are summarized below: (1) means of wood traits were all significantly lower in gymnosperms than in angiosperms. (2) Air-dried density (ADD) and tangential shrinkage coefficient (TSC) are key traits that summarize the correlations among wood traits for gymnosperms, while ADD and radial shrinkage coefficient (RSC) represent those for angiosperms. The allometric slopes of other traits, except for hardness of transverse section (HES), against ADD for gymnosperms were significantly steeper than or similar to the corresponding slopes for angiosperms. On the contrary, the slopes of other traits (except TSC) against RSC for gymnosperms were shallower than or similar to their counterparts for angiosperms. Generally, wood traits were positively related with each other, except that TSC was negatively related to density-related (ADD, BD) and hardness-related traits (HES, HRS and HTS) in gymnosperms. (3) Phylogeny had significant effects on some wood traits of gymnosperms, but had no effects on traits of angiosperms. The present analyses demonstrated a systematic difference in wood traits between two major plant categories, which suggests the evolutionary divergence (TSC, RSC) and convergence (ADD) in key functional traits among woody plants.

Screw and Nail-Holding Capacities of Combi Plywood Produced From Eucalyptus, Beech and Poplar Veneer

Combi plywood (combination plywood) consists of plywood made of two or more veneer sheets peeled from different species of wood. Combi plywood has some advantages such as its low weight, low cost, satisfactory performance, and the availability of abundant raw materials. In this study, five-ply combi plywood panels were produced from eucalyptus, beech, and poplar using urea formaldehyde adhesive to combine rotary-peeled veneer sheets. Three plywood groups were produced with different combinations, and we investigated the screw withdrawal and nail holding capacity of the combi plywood. In addition, we determined the air-dried density and equilibrium moisture content of the plywood panels that were produced. The test results were analyzed using the SPSS software program. We used the data that were obtained to determine the combi plywood that provided the greatest screw and nail holding capacities. In addition, we investigated the relationship between density and fastener holding capacity.

Validation of ultrasonic velocity estimates of wood properties in discs of radiata pine

BackgroundMeasurement of microfibril angle (MFA) in the S2 layer of the cell walls of wood using speed of sound in wood has become a common way to estimate wood stiffness and stability. Measurements across the radius of a disc can be critical, but sonic testing needs to be validated against direct measurements of MFA.MethodsA robotic machine that uses two transducers to detect the speed of sound through discs of wood from tree stems was validated by comparing its measurements with wood MFA, air-dry density, and modulus of elasticity assessed by X-ray diffractometry through the “Silviscan” system.ResultsUltrasonic velocity (USV) was highly correlated with MFA but not with air-dry density. Variable moving averages were assessed in order to estimate the resolution of the USV measurements, and it appeared that the diameter of the swath detected by the transducers was between 23 and 30 mm.ConclusionsIt was concluded that MFA in wood samples can be assessed rapidly and cheaply using USV measurements but at lower resolution than assessments using X-ray diffractometry.

Experimental Evaluation of Thermal Performance and Durability of Thermally-Enhanced Concretes

The thermal performance and durability of the thermally-enhanced concrete with various insulating materials were evaluated through a series of tests. Three types of insulating materials—diatomite powder, hollow micro-spheres, and a micro-foam agent—were used for both normalweight aggregate concrete (NWAC) and lightweight aggregate concrete (LWAC). The thermal conductivity was measured by two different test methods: quick thermal conductivity meter (QTM) and guarded hot wire (GHW) methods. Then, the results were compared with each other. All insulating materials used in this study proved their ability to reduce the thermal conductivity. Additionally, it can be found that the trend of a decrease in air-dry density is similar to that of thermal conductivity of thermally-enhanced concrete. Additional thermal transmission tests with seven large-scale specimens were conducted by using the calibrated hot box (CHB). However, from this tests, it was seen that thermal transmission reduction for tested specimens were not large compared to the thermal conductivity reduction measured by QTM and GHW, due to multiple heat transfer. To examine the durability of thermally-enhanced concretes, accelerated carbonation and freeze-thaw cycle tests were conducted. From the results, it can be found that the thermally-enhanced concrete shows good freeze-thaw resistance. However, the carbonation rates of the concretes increased rapidly and additional methods to improve the carbonation resistance should be considered.

Density and some mechanical properties of densified and heat post-treated Uludağ fir, linden and black poplar woods

The effects of thermo-mechanical densification and heat post-treatment on air-dry density, modulus of elasticity (MOE), bending strength (MOR), and compression strength parallel to the grain (CS) of Uludag fir (Abies bornmulleriana Mattf.), linden (Tiliagrandifolia Ehrh.), and black poplar (Populus nigra L.) wood samples were investigated. Samples were densified with compression ratios of 25 and 50%, and at 100 and 140 °C. Then, the heat treatment was applied to the samples at 185 and 212 °C for 2 h. According to the results of the study, density of all wood samples increased together with the increase of compression ratio. Regarding compression temperature, the highest density increase was obtained at 100 °C. Mechanical strength (MOE, MOR, and CS) in densified samples increased depending on compression ratio and increase of density. The highest strength increase was in black poplar samples and the lowest was in linden samples. After heat post-treatment, mechanical strength of samples decreased depending on increase in treatment temperature. However, strength values (MOR except) of samples which are 50% compressed and heat-treated were found higher than control samples.