THE STUDY ON THE DAMAGE CHARACTERISTICS OF PINUS SYLVESTRIS VAR. MONGOLICA UNDER DIFFERENT MOISTURE CONTENTS

Laboratory studies have shown that wood has hygroscopic properties. When used as a construction material in buildings, it can thus influence indoor relative humidity and temperature. Ventilation can affect indoor climate if the temperature differ between indoor and outdoor air. The coating of indoor wood may also affect its hygroscopic properties. Few studies of wood in real buildings have been conducted. The main aim of this experimental study was to explore the association between moisture content in indoor air and wood in two classrooms. The floor plan of the two classrooms was identical. In one classroom, all wood surfaces were untreated, whereas, in the other, they were treated with a transparent varnish. Sensors measured indoor air relative humidity, moisture content in the wood, and temperature in the air and wood in both classrooms. Linear regression analysis was performed to explore possible associations. Strong positive associations between indoor air relative humidity and the moisture content in wood in the untreated classroom were found. Weak positive associations were evident in the classroom with treated wood. Ventilation reduced these associations.

Norway spruce (Picea abies (L.) Karst.) stump wood is a potential source of bioenergy in Finland. The heating value of stump wood depends on, among other things, the moisture, carbon and ash content of the wood. In this study the moisture content of Norway spruce stump wood was examined immediately after harvesting at the clear cutting area and after different drying times at the roadside storage sites. Immediately after stump harvesting the average moisture content (wet basis) was 53%. The stump wood dried fairly fast during spring and summer. One month after stump harvesting, the average moisture content was about 31%. If the stump wood had dried well once, water absorption became very weak and the moisture content increased only slightly in the late autumn. Each spring and summer the moisture content of the stumps was lower than during the previous year. Annually the lowest moisture content was observed at the beginning of July and the highest at both the beginning and the end of the year. The moisture content of stump wood followed an upwards opening parabola over a one year period and was repeated each year. Three years after harvesting the heating value of the stump wood was still 5.241 MWh/ton. Overall, when harvesting took place in the spring or early summer, the stump wood was combustible after a one month drying period immediately after harvesting.

Wooden façades are gaining in importance. Thermally modified wood is becoming one of the preferred materials for claddings. In spite of the fact that façades made of thermally modified wood have been in use for more than two decades, reports about long-term monitoring have been sparse. The results of three-year monitoring of a façade made of thermally modified wood in Ljubljana are reported. Moisture content measurements of thermally modified façades were taken at 22 locations and compared to the moisture content of untreated Norway spruce wood. Temperature and relative humidity were recorded in parallel. The moisture content of the wood was compared to the average relative humidity before the measurements. The results confirm the lower moisture content of thermally modified wood in comparison to reference Norway spruce. The moisture content of the wooden façade could be best correlated with the average relative humidity and temperature 48 h before the wood moisture content measurement was taken.

Determining correct moisture content of wetted building materials and analysis of corresponding locations, orientations, and patterns is of imminent value to Forensic Engineers and building scientists. As many building damages relate to insurance claims and construction defect/ subrogation lawsuits, legal challenges to the accuracy of measured moisture content have arisen. The objective of this study was to independently establish the level of precision of common moisture meters used to quantify and measure moisture content in building components. The study tested four different brand moisture meters in gypsum and wood substrates at normal, high, and saturated moisture contents. The results were compared against laboratory obtained moisture content to assess the accuracy of each meter in the substrate and at which moisture content range.The study wetted wood and gypsum specimens to moderate and saturated conditions and measured the resulting moisture content with the four different brands of meters. Control wood and gypsum specimens were not exposed to water and their moisture content was measured as is. All of the wood and gypsum specimens were subsequently sent to a laboratory and moisture content was calculated by the oven-dry method. The moisture content results measured by moisture meters were compared against the laboratory obtained data. Data was averaged and plotted with moisture content of various specimens and visually analysed to determine which meters deviated from the laboratory data and at which moisture contents. Data was also numerically analysed and graphed to quantify meter moisture content accuracy as compared to laboratory obtained moisture content.Moisture meters should be used within the manufacturer specified range of moisture content and price may not be the best indicator of moisture meter accuracy. At low ranges of moisture content in wood and gypsum, all meters exhibited relatively small deviation from laboratory calculated values, while moderate and saturated conditions presented larger variations from laboratory moisture content. Composite materials such as gypsum may be difficult to establish moisture content, as different materials such as the gypsum core and paper facing absorb and distribute moisture differently. All meters were successful in detecting wet conditions, but exhibited a lack of precision in determining exact values in moderate and saturated conditions. In this regard, meters may be improved as the industry demands not only detecting wet conditions but determining precise values at a full range of moisture contents. Future studies may be limited to monolithic materials as oven dry method returns an average value of the respective paper and gypsum components in gypsum board specimens, and thus contained an inherent margin of error.

An emergency swine mortality composting study at Iowa State University was conducted to evaluate the performance of six on-farm carbon source or “envelope” materials (corn silage, oat straw, cornstalks, wood shavings, soybean straw, and alfalfa hay) when used in a plastic-wrapped passively-ventilated emergency composting system that was first employed for emergency disposal of poultry in British Columbia in 2004. With the exception of tub grinding to reduce the particle size of long and fibrous materials, they were used “as is,” in their normal state — as would likely be the case during an emergency — without benefit of mixing or preconditioning to optimize C:N ratios or moisture content. Moisture content fell into two distinct groups: wood, soy, and alfalfa products had initial moisture content of < 20%; while the other materials ranged from 55-62%. After 8 weeks moisture ranged from 11-18% and 27-35% respectively for the two groups. Minimum O2 concentrations occurred during the first 2 weeks of composting, and ranged from 9-16% in relatively fine-grained wood and silage materials, to 17-20% in the others. Daily temperatures in material surrounding the carcasses also were highest during the first two weeks. Mean temperature ranges during the initial 30 days of composting were 47-57 °C for the moist group, and 35-43 °C for the dry group. Total soft-tissue degradation ranged from 77-78% for silage, wood shavings, and alfalfa hay, and from 85-88% for the other three materials. The highest degradation occurred in two materials having high initial moisture, and high mean 30-day temperatures, while the lowest degradation occurred in two materials having low 30-day mean temperatures and low initial moisture. The temperature/moisture correlation was not consistent, however, as soy straw — exhibiting both low mean temperature and low initial moisture — had high carcass degradation, and silage — having high temperature and high moisture — was in the group producing lower degradation. Remains recovered from all test units after 8 weeks appeared to be desiccated, suggesting that carcass decomposition was terminated by low moisture. This is consistent with the low final moisture levels, and indicates that moisture coming from the carcasses plays a significant role in sustaining decomposition. It also suggests that airflow rates through the matrix may have been excessive and that measures need to be taken to reduce airflow and prevent excessive moisture loss. Success rates meeting USEPA Class A or B criteria for pathogen reduction were much higher for the moist materials than for dry ones, indicating that procedures for emergency composting of carcasses resulting from disease should include pre-moistening of carcass surfaces and envelope materials, and to taking measures to control excessive airflow through the composting matrix that can result in premature drying of envelope materials.

A rectangular waveguide antenna was tested for eucalyptus wood moisture content (MC) measurement before being used. To improve the moisture content measurement of the rectangular waveguide antenna, a woodpile-shaped Electromagnetic Band Gap (EBG) was installed by Transverse Electric (TE) arrangement. This antenna is responsible for receiving and transmitting signals which are converted from electrical energy into radio frequency energy transmitted through the air. In this research, we take advantage of the wave propagation of antennas in the air and use them to propagate waves through wood materials. To compare signal transmission power to determine moisture content in wood and the benefit of the EBG is that it acts like a convex lens to increase the strength of the waves so that they can penetrate the wood more efficiently. The results showed that woodpile-shaped EBG could increase the efficiency of receiving and transmitting signals, reduce working hours for farmers and reduce costs by about 90 %. When this antenna was tested and actually used, it was found that the frequency band that responded best to the moisture content value was 2.20 GHz. This antenna was built with an aluminum material of size 9×4×15 cm3 and 2×6 units woodpile EBG on a 9.54×4 cm2 Polyester Mylar base plate. There was a gain of 7.81 dBi from the original structure, or by 20 %. At a radius of 4 cm, the values ​​of moisture content ranged from –9.46 to –42.19 dBm. At a radius of 6 cm, the values ​​were –9.41 to –42.89 dBm. At a radius of 8 cm, the values ​​ranged from –9.39 to –43.01 dBm, respectively. All 3 values ​​were found to be efficient. The size was not less than 84 % compared to the general standard meter. HIGHLIGHTS A rectangular waveguide antenna was tested for eucalyptus wood moisture content (MC) measurement before being used. To improve the moisture content measurement of the rectangular waveguide antenna, a woodpile-shaped Electromagnetic Band Gap (EBG) was installed by Transverse Electric (TE) arrangement. This antenna is responsible for receiving and transmitting signals which are converted from electrical energy into radio frequency energy transmitted through the air. In this research, we take advantage of the wave propagation of antennas in the air and use them to propagate waves through wood materials. To compare signal transmission power to determine moisture content in wood and the benefit of the EBG is that it acts like a convex lens to increase the strength of the waves so that they can penetrate the wood more efficiently. The results showed that woodpile-shaped EBG could increase the efficiency of receiving and transmitting signals, reduce working hours for farmers and reduce costs by about 90 %. When this antenna was tested and actually used, it was found that the frequency band that responded best to the moisture content value was 2.20 GHz. This antenna was built with an aluminum material of size 9×4×15 cm3 and 2×6 units woodpile EBG on a 9.54×4 cm2 Polyester Mylar base plate. There was a gain of 7.81 dBi from the original structure, or by 20 %. At a radius of 4 cm, the values of moisture content ranged from –9.46 to –42.19 dBm. At a radius of 6 cm, the values were –9.41 to –42.89 dBm. At a radius of 8 cm, the values ranged from –9.39 to –43.01 dBm, respectively. All 3 values were found to be efficient. The size was not less than 84 % compared to the general standard meter. GRAPHICAL ABSTRACT

There has been a longstanding interest in developing a fast and accurate method for measuring moisture content in wood. The gravimetric method that is commonly used today is a widely accepted industrial standard but it is time consuming. In this study, we tested and evaluated Mantex Desktop Scanner that is based on dual energy X-ray absorptiometry as a potential technique for fast and accurate determination of moisture content at different temperatures in wood chips of Pinus sylvestris, Picea abies and a variety of mixtures thereof. The results of the study give similar results as the gravimetric method when determining the moisture content in wood. They further show that there was no significant influence on the result if samples were measured while frozen or at room temperature.

One of the natural properties of wood and wood-based materials is their soaking capacity (hy­gro­sco­pi­ci­ty). The moisture content of wood and building constructions of wood and wood based materials significantly influences the service life and reliability of these constructions and buildings. The equilibrium weight moisture content of built-in wood corresponding to temperature/moisture conditions inside the cladding has therefore a decisive influence on the basic requirements placed on building constructions. The wood in wooden frame cladding changes its moisture content depending on temperature and moisture conditions of the environment it is built into. The water vapor condensation doesn’t necessarily have to occur right in the wooden framework of the cladding for the equilibrium moisture content to rise over the level permissible for the reliable function of a given construction. In spite of the fact that the common heat-technical assessment cannot be considered fully capable of detecting the effects of these factors on the functional reliability of wood-based constructions and buildings, an extension has been proposed of the present method of design an assessment of building constructions according to the ČSN 73 0540 standard regarding the interpretation of equilibrium moisture content in relation to the temperature/moisture conditions and their time behavior inside a construction.

ABSTRACTThe estimation of the pixel-wise distribution of the moisture content (MC) in wood using X-ray computed tomography (CT) requires two scans of the same wood specimen at different MCs, one of which is known. Image-processing algorithms are needed to compensate for the anisotropic distortion that wood undergoes as it dries. An alternative technique based on dual-energy CT (DECT) to determine MC in wood has been suggested by several authors. The purpose of the present study was to evaluate the hypothesis that DECT can be used for the determination of MC in real time. A method based on the use of the quotient between the linear attenuation coefficients (μ) at different acceleration voltages (the so-called quotient method) was used. A statistical model was created to estimate the MC in solid sapwood of Scots pine, Norway spruce and brittle willow. The results show a regression model with R2 > 0.97 that can predict the MC in these species with a RMSE of prediction of 0.07, 0.04 and 0.11 (MC in decimal format) respectively and at MC levels ranging from the green to the totally dry condition. Individual measurements of MC show an uncertainty of up to ±0.4. It is concluded that under the conditions prevailing in this study, and in studies referred to in this paper, it is not possible to measure MC with DECT.

Variation in density and moisture content of Eucalyptus grandis wood and bark is described utilizing the trees established for a half-sib progeny test in southern Florida. Differences in density and moisture content among progenies were significant. Variations in wood properties were largely due to the genetic differences. No relationship was found between wood density and wood moisture content. Implications for genetic manipulation of wood quality for this species were discussed.

This study aims to present a low-cost, non-destructive microwave sensor implementation to monitor the real-time moisture content of rubber wood in industrial dehydration processes. The proposed sensor is based on the free-space measurement technique with magnitudes S11 and S21 only. The novelties of this study consist of the natural frequency determination of rubber wood and the design of a sensor system using devices available on the market with reasonable cost performance. The natural frequency was determined using a simulation and was equal to 1.25 GHz. It specified the sensor system design and device selection. The designed system was initially verified by measuring the moisture content of rubber wood in the laboratory. The measured S11 and S21 voltages correlating with moisture content percentages were obtained and programmed. The system was then installed to monitor the moisture content of rubber wood in the dehydration process. The measured results deviated from those obtained from a standard method in the range of 7.67-15.38%. The error compensation was analyzed to improve the measured results that provided the deviated moisture content in the range of 3.58-5.21%. It can be inferred that the proposed sensor system has the capability to be implemented in industrial dehydration processes.

The author presents an analysis of the main dependences of humidity in wood materials during operation. The article discusses the physical processes that take place during drying/wetting wood and the types of moisture in wood. The article examines the dependence of the equilibrium moisture content of wood on environmental humidity. This dependence is reflected using graphs. It should be noted that the equilibrium moisture content during drying and moistening wood differs by moisture hysteresis. As discussed in the article, when the environmental humidity changes, the humidity in the lumber also changes with a certain delay. This delay is expressed by the equation of the dependence of time on the initial and final moisture content of the wood and the humidity of the environment, as well as the geometry of the lumber in question. To derive this dependence, the differential equation of moisture content in wood is taken as a basis, and later in the article a step-by-step derivation of the dependence of time on changes in moisture content in wood is shown. The article also discusses the prerequisites under which this dependence is derived: humidity below the saturation point, regular drying mode, which is common and uniform initial distribution, no influence of temperature changes on moisture conductivity at small temperature gradients, no moisture transfer under the influence of internal excess pressure. It should be noted that this dependence for drying and moistening differs slightly and these differences are also discussed in the article.

The equilibrium moisture content in wood depends not only on the current relative humidity in ambient air, but also on the history of relative humidity variations. This hysteresis dependence of sorption in wood implies that in the worst case the moisture content for a given relative humidity may deviate by 30–35%. While researchers seem to have reached a general agreement on the hypothesis for the sorption hysteresis phenomenon, only a few models describing the phenomenon are available. Current models such as the independent domain model have numerical deficiencies and drawbacks. This paper presents a new hysteresis model, which mathematically resolves in closed-form expressions, with the current relative humidity and moisture content as the only input parameters. Furthermore, the model has the advantage of being applicable to different sorption isotherms, i.e., different species and different temperatures. These features make the model relatively easy to implement into a numerical method such as the finite element method.

ABSTRACTCurrently computed tomography (CT) scanning provides a non-destructive method to determine moisture content in wood in three dimensions. With the current methodology two measurements are needed, one with the scanned piece of wood’s moist state and one after drying. Then the difference of the images can be calculated. The drawback and challenge is that dimensional changes due to shrinkage of wood in the drying process have to be compensated for by image processing. In this study a dual-energy CT scanning method is tested based on the consecutive scanning of wood samples at different energy levels to differentiate water from wood, without the necessity to dry the sample and thus without the need for complex image correction. Not quantified but visible differentiations due to moisture content were obtained on small cubical pine samples of different densities by quick consecutives scans at 60 and 200 kV. The results suggest that given that the pixels in the CT images are representing absorption coefficients it should be possible to directly measure moisture content in wood non-destructively in small volume elements inside solid wood in three dimensions. Further applications of this technique in industrial CT scanning of wood are discussed.

The moisture content (MC) of wood affects its industrial performance, but it is difficult to monitor spatial variations in MC. Here, a multivariate regression was developed to estimate the MC from near infrared (NIR) spectra and was used to monitor the spatial variation in the MC of wood during air- and oven-drying. The spectra and mass of wood pieces were measured at five stages during drying (at each 20% loss of initial water mass). Wood pieces were dried naturally and oven-dried at 60 °C. Initially, 25 spectra were recorded at equidistant points covering the entire longitudinal × radial surface of the sample. Then, a planing machine was used to access the inside of the wood, and NIR spectra were measured for each new surface, at a total of 100 points spatially distributed within the wood pieces. The wood pieces were analyzed in their original state, and when they had lost 20, 40, 60, and 80% of their initial water mass. An NIR-based regression (R 2 p = 0.90 and RMSEP = 10.51%) was applied to estimate the MC, and its spatial gradient during drying was then mapped. These analyses revealed the spatial variation in MC within wood pieces during drying.