Wood Moisture Content Research Articles

Moisture-induced stresses and damage in adhesively bonded timber-concrete composite connection

An experimental program was conducted to clarify the wood swelling effect on the shear strength and failure modes of adhesively bonded timber-concrete composite (TCC) joints. A total of 150 TCC joints were fabricated and cured in the condition of 20 °C & 55% relative humidity (RH) for one month, then the joints were divided into three groups (50 each group) and treated at 20 °C and 55%, 75%, and 95%RH, respectively. After about 30-, 100-, 200-, 300-, and 390-day treatment, ten samples from each group were tested to determine their shear strength and failure modes. It was found that an increase in moisture content (e.g., by 10.8%) caused a reduction of shear bond strength (e.g., by 25%). Concrete failure was found to be the dominant failure mode for all tested joints. Finite element (FE) analyses were performed to facilitate understanding of the underlying mechanisms of wood swelling effects. When the moisture content of wood increased by 10.8%, the FE analyses showed that the wood swelling resulted in significant internal stresses and concrete tensile damage at the wood/concrete bonding interface, which was the main reason for the reduction of the shear bond strength. In addition, the effects of essential factors, such as material properties of adherents, orientation of wood components relative to the bonding surface, and bonding width perpendicular to the grain direction of wood, on the moisture-induced stresses were studied. Concrete grades hardly had influence. For the bonding process of TCC structure in practice, a smaller orientation angle (i.e., the angle between the radial direction and the bonding surface) is recommended to avoid moisture-induced damage in wood and concrete at their interface. In other words, the surface of a Glulam or CLT product designed for bonding should be as close as possible to R-L planes of the constituent wood blocks and avoid T-L planes. Furthermore, a larger bonding width resulted in higher moisture-induced stresses.

Effect of wood moisture content and adhesive open time on the adhesion strength of wet bonded Pinus radiata wood

AbstractGluing wood in the wet state can reduce warping, splitting, and increase processing volume recovery. Adhesive open time and moisture content may play an important role in bond line strength, but there are no specifications for wet wood bonding. Wood specimens at two different moisture contents were glued with three polyurethane adhesives and tested in shear on the bond line. Open time of 15 min was superior to 4 and 40 min. All adhesives performed better when wood was glued at 30% moisture content than at 101%, but only the 15- and 40-min open time met the minimum shear requirement.

The Impact of Wood Moisture Content on the Productivity and Costs of Forest Energy Supply Chains in Southeast Brazil

Using wood for power generation necessitates a more efficient production chain in the various steps: harvesting, forwarding, storage, chipping, transport, and conversion systems. In this context, the moisture content (MC) of wood can impact the harvesting operation, the volume to be chipped, the transportation of raw materials, the storage time, and other factors, thereby influencing the economic aspects of the chain. The primary objective of this study is to investigate the influence of wood moisture content on the yield and costs of different forest operation chains for power generation in São Paulo State, Brazil. Our findings reveal that harvesting and forest transport are the primary cost components (over 80%) in the supply chains under study. We observed a difference of up to 17.6% in the unit cost of the energy generated among the studied supply chains. In economic and sustainable terms, our results suggest that logs should be stored in the field for three to four months and the transport distance to the power plant should not exceed 100 km.

Effect of targeted acetylation on wood–water interactions at high moisture states

Acetylation is a wood modification used to increase the durability. Although it is known that the wood moisture content is lowered, the exact mechanisms behind the increased durability are not known. However, since fungi need water in different locations for different purposes the location and state of water is most probably of importance in addition to the total moisture content. In a previous study, we used targeted acetylation to alter the wood–water interactions in different parts of the wood structure in water saturated and hygroscopic moisture states. The main range for fungal degradation is, however, between these moisture ranges. This study investigated the effect of targeted acetylation on location, state and amount of water at non-saturated, high moisture states using the pressure plate technique. Specimens were modified using acetic anhydride by two approaches: (1) uniform modification (2) interface modification acting on the cell wall-lumen interface. They were then conditioned to eight moisture states between 99.64 and 99.98% relative humidity in both absorption and desorption and the location and state of water was studied using Low Field Nuclear Magnetic Resonance, X-ray computed tomography and Differential Scanning Calorimetry. Capillary water was present at all the included moisture states for all specimen types, but the amounts of capillary water in absorption were small. Increasing degree of interface modification increased the amount of capillary water compared to untreated wood. In addition, the uniformly modified wood often had higher amounts of capillary water than the untreated wood. The amount of cell wall water was decreased by uniform modification, but slightly or not reduced by the interface modification. The combination of targeted modification and conditioning to high well-defined moisture states thus gave very different amounts of capillary water and cell wall water depending on the conditioning history (absorption or desorption) and choice of modification. This opens new possibilities for designing materials and moisture states for fungal degradation experiments of wood.

Wood modification with trimethoxyphenylsilane via supercritical carbon dioxide for enhanced weathering resistance

Abstract This research focuses on increasing wood resistance against UV degradation using trimethoxyphenylsilane as modifying agent and supercritical CO2 as a green solvent and reaction medium. Trimethoxyphenylsilane was successfully grafted on European spruce (Picea abies, H. Karst) and was characterized by SEM-EDX and UV–vis reflectance. SEM-EDX showed the presence of silicium inside the wood cell wall. Increased wood moisture content showed positive effect on weight gain of trimethoxyphenylsilane after treatment. UV resistance of treated wood was evaluated by following the color change during artificial weathering. Modified samples showed improved weathering resistance compared to unmodified wood with a ΔE value around 5 after 260 h. Processing and modifying wood using supercritical CO2 is a promising route to increase wood performances and increase its use as a building material.

How accurate are automated sorption balances? An analysis of errors in wood moisture content from uncertainties in the conditioning environment

Automated sorption balances are increasingly used to determine sorption isotherms of hygroscopic materials like wood. The sorption isotherms are constructed based on a number of equilibrium states between a specimen and the surrounding conditioning environment. In recent years, the uncertainty of these equilibrium states has been thoroughly discussed related to the time at constant environmental conditions needed to reach an adequate mass stability. However, uncertainties related to the conditioning environment are rarely discussed. This study describes a framework for analyzing and quantifying the effect of these uncertainties on the error in determined equilibrium moisture content. Various effects of the conditioning environment are analyzed, and the most important effects relate to the relative humidity (RH) in the instruments, both in terms of fluctuations in RH and an offset from the target value. The moisture error for these effects was found within the range 0.001–0.01 g g−1.

Optimizing solar energy for wood drying under various climates: A comparative study of flat plate and photovoltaic thermal solar collectors

Wood drying is an important operation in many sectors, and harnessing solar energy for this purpose has received a lot of interest due to its sustainability and cost-effectiveness. In this work, we compare how two solar collector configurations namely, Flat Plate Collector and Photovoltaic Thermal collector, perform in a solar wood drying system. The moisture content of wood was reduced from 73% to 12% in four different regions: Errachidia, Meknes, Tangier, and Rabat. The Gauss–Seidel method is used to solve the governing equations for heat transfer after discretizing them via implicit finite differences. The effectiveness of the solar collectors was simulated through the TRNSYS software, and a numerical program was generated using the Python programming language. According to our research, the FPC beats the PVT collector because of its higher output temperatures dramatically shorten the time it takes for wood to dry. The study emphasizes how temperature and humidity affect drying, showing that faster drying occurs in hotter, drier locations. Furthermore, drying time can be saved by using FPC and PVT collectors compared to conventional open sun drying.The primary conclusions of this research are: In the FPC solar dryer, the drying time needed in Errachidia, Meknes, Rabat and Tangier was 144 h, 162 h and 171 h, respectively. While in the PVT solar dryer, it required 162 h in Errachidia, 171 h in Meknes, 180 h in Rabat and 189 h in Tangier. Further, the FPC collectors showed a range of 293 K to 347 K for the outlet temperature. The PVT collectors, however, showed a variable range between 295.9 K and 320 K. The drying periods and temperature ranges examined revealed that Errachidia was the most advantageous location, regardless of whether FPC or PVT collectors were used. In fact, the drying time that can be saved by using FPC is 41% while PVT is 31% compared to traditional open sun drying.

Wood trait preferences of Neotropical xylophagous beetles (Coleoptera: Cerambycidae).

Tree life history strategies are correlated with functional plant traits, such as wood density, moisture content, bark thickness, and nitrogen content; these traits affect the nutrients available to xylophagous insects. Cerambycid beetles feed on substrates that vary in these traits, but little is known about how they affect community composition. The goal of this project is to explore the community composition of two cerambycid subfamilies (Cerambycinae and Lamiinae) according to the wood traits in the wood they eat. In a salvage project conducted adjacent to the Panama Canal, trees were felled and exposed to Cerambycidae for oviposition. Disks from branches of differing thickness from the same plant individuals were used to calculate wood density, moisture content, and bark thickness in the field; nitrogen data were acquired offsite. Thick and thin branches tended to differ in wood trait values; therefore, data were analyzed separately in subsequent analyses. In thin branches, cerambycid abundance and species richness were higher in samples with less dense, moister wood, and thicker bark. Thick branches showed similar trends, but the wood traits accounted for little variability in beetle abundance or species richness. There were no significant regressions between beetle data and nitrogen. Cerambycines emerged more slowly, and from denser, drier wood, than lamiines. Cerambycines might be more drought-tolerant than lamiines, and therefore more resistant to the longer, more severe dry seasons that are predicted to occur due to climate change.

Moisture safety strategy for construction of CLT structures in a coastal Nordic climate

To reduce the carbon impact of new buildings, wood is seeing increased use as a structural material. Cross-laminated timber (CLT) and glue-laminated wood (glulam) elements allow the construction of multi-storey buildings. However, wood is vulnerable to moisture, especially when naked wood is exposed to weather during the construction process. This paper presents the moisture strategy employed during the construction of a four-storey CLT/glulam building in Trondheim, Norway. The building was constructed without the use of a weather-protective tent, requiring alternative protective measures. The construction of the main structure was scheduled to be as short as possible. Local protective measures were employed to protect the structure from rain and free water was removed after rain events. The project was closely supervised by the client, with particular care for moisture control. Moisture was regularly measured at 50 points throughout the building. No wooden surfaces were encapsulated until a wood moisture content below 15 weight-% was measured. The performance of the moisture strategy was evaluated using measurements of wood moisture, indoor climate, airtightness, and visual inspections. The wood moisture content quickly decreased as the building envelope was assembled, indicating that drying was well facilitated. In the first year after construction, gaps between the flooring and baseboards were observed, suggesting that the wooden elements have experienced some shrinkage. The moisture safety strategy is deemed to have been generally successful. The overall experiences were important in the development of new recommendations in the SINTEF Building Research Design Guides for CLT structures.

Biochar and manure additions increased above‐ and belowground wood decomposition, and soil enzyme activities in a sandy loam soil

AbstractWhile biochar and manure can provide considerable benefits to soil properties, how these amendments may alter soil microbial activity and decomposition processes remains unknown. In a split‐split‐split‐plot experiment, we amended a sandy loam soil with three rates of manure (whole plot; 0, 3, 9 Mg ha−1) and biochar (split‐plot; 0, 2.5, 10 Mg ha−1), and installed three species of wood stakes (split‐split‐split plot; triploid poplar, Populus tomentosa Carr.; trembling aspen, Populus tremuloides Michx.; and loblolly pine, Pinus taeda L.) on the soil surface and in the mineral soil (split‐split plot) to serve as a substrate for microbial degradation. Wood stakes were sampled 3 years after installation to assess decomposition rates (mass loss), and changes in wood carbon (C) and nitrogen (N). In addition, soil extracellular enzyme activities at the 0–20 cm depth were examined. Biochar alone, especially 10 Mg ha−1, increased wood stake decomposition and moisture content on the soil surface and in the mineral soil. Manure at the rate of 9 Mg ha−1 increased soil N‐acetyl‐β‐D‐glucosaminidase, α‐glucosidase, and aryl sulfatase activities by 91%, 17%, and 48% respectively. Because of the synergistic benefits of biochar and manure, we suggest that, in this climatic regime and soil texture, 10 Mg ha−1 biochar can be used for soil C sequestration and soil quality improvement, and 9 Mg ha−1 manure can be used in combination with biochar to build soil organic matter in plantations.

Gluing characteristics of Papua New Guinea timber species for various non-structural applications

Papua New Guinea (PNG) has abundant natural forest resources but there are many constraints which need to be addressed to support the development of competitive value-added wood industries. There is a need to develop knowledge and capacity in wood science and processing technologies which support successful domestic value-adding wood processing enterprises. A comprehensive testing program has been developed to assess the glue‐bond strength and performance of selected commercial PNG timber species in various climatic conditions to simulate service conditions in potential market destinations. Two criteria namely shear strength and wood failure have been used to determine if a species can meet the minimum requirements for either dry use or wet use applications. The performance of 24 different PNG commercial timber species has been assessed using a one-component cross-linking polyvinyl acetate emulsion adhesive. The bondability of the selected species has been carefully estimated considering the wood density and wood moisture content for the strength and durability in dry- and wet-use conditions. The testing results show that as the wood density as a wood property factor and moisture content as a service condition factor increase, high shear strength with high wood failure become more difficult to achieve consistently. The highest shear strength and wood failure results were achieved by softwood plantation species and low-density hardwood species. Based on the testing results, the selected species have been classified into bondability classes (bond very well, bond well, bond with difficulty, very difficult to bond).

Prediction of wood drying process based on artificial neural network

Taking the conventional drying process of Pinus sylvestris square wood with pith as the research material, based on the Back Propagation (BP) neural network algorithm, a model was constructed using the real-time online-measurement data. Softening treatment time and temperature, variable treatment time and temperature, initial moisture content of wood, and position of wood core and sapwood were used as model inputs. Wood drying rate and longitudinal cracking degree were used as outputs to indicate wood drying quality. The results showed that with a suitable model structure of 6-9-2 (input layer-hidden layer-output layer), the coefficient of determination R2 and mean square error of the test samples were 0.96, 0.99, and 0.00605, respectively, indicating that the neural network model has good generalization ability. Compared with the experimental value, the predicted value basically conforms to the change law and size of the experimental value, and the error distribution is approximately 2%. This shows that the BP neural network model can simulate the drying rate and longitudinal cracking degree in the drying process and realize the prediction of the drying process.

Does the moisture content of mercerized wood influence the modulus of rupture of thermopressed polyurethane-based composites?

Wood residues hold great potential for the development of composites. However, reinforcing wood requires modifications to enhance its adhesion to the polymeric matrix. In thermopressing, composites reinforced with wood are processed over a wide range of moisture levels. Nevertheless, there are limited studies on how varying this parameter influences the mechanical properties of these composites. This research provides valuable insights into how the moisture content present in wood reinforcement during the thermopressing process affects the adhesion of the composite through the modulus of rupture, a contribution not previously found in the literature. Therefore, our study aims to investigate the effects of different NaOH concentrations (5% and 10%) and the moisture content levels (3% and 12%) during thermopressing on the modulus of rupture of polyurethane-based composites. We analyzed three types of tropical wood residues from the Amazon, both with or without mercerization treatment, using thermal (TG/DSC), structural (XDR and FTIR), and morphological (SEM) characterizations. Subsequently, we evaluated the impact of moisture content on the modulus of rupture. The concentration of NaOH modifies the thermal, structural, and morphological characteristics of the wood residues, but these modifications were more effective in the composite when the moisture content of the fibers was low (3%). Reducing the moisture content of the reinforcement increased the resistance and the modulus of rupture of the composites made from Louro Itaúba (from 2 to 9 MPa), Louro Gamela (from 12 to 16 MPa), and Massaranduba (from 3 to 11 MPa). Therefore, mercerization alone was insufficient to boost the modulus of rupture of polymeric composites. Instead, the control of moisture content emerged as the crucial factor during the thermopressing process.

Soil amendment with biochar and manure alters wood stake decomposition and fungal community composition

AbstractBiochar and manure can be used for sustainable land management. However, little is known about how soil amendments might affect surface and belowground microbial processes and subsequent wood decomposition. In a split‐split‐split plot design, we amended soil with two rates of manure (whole plot; 0 and 9 Mg ha−1) and biochar (split plot; 0 and 10 Mg ha−1). Wood stakes of three species (hybrid poplar, triploid Populus tomentosa Carr.; aspen, Populus tremuloides Michx.; and pine, Pinus taeda L.) were placed in two positions (horizontally on the soil surface, and inserted vertically in the mineral soil), which served as a substrate for fungal growth. In 3 years, the decomposition rate (density loss), moisture content, and fungal community (via high‐throughput sequencing methods) of stakes were evaluated. Results indicated that biochar and/or manure increased the wood stake decomposition rates, moisture content, and operational taxonomic unit abundance. However, the richness and diversity of fungi were dependent on wood stake position (surface > mineral), species (pine > the two Populus), and sample dates. This study highlights that soil amendment with biochar and/or manure can alter the fungal community, which in turn can enhance an important soil process (i.e., decomposition).

Casehardening characterization in western hemlock wood

Casehardening (σi) is an internal stress-related phenomenon that develops in kiln-dried wood materials, causing shape distortion. This study focuses on the impact of drying schedule and wood parameters (e.g., density, moisture) on σi. Results indicated that the wood's final moisture content level has the highest impact when it is above 15%. However, the wood moisture gradient is the most influential factor when wood's moisture content is below 15%. Drying schedule aggressiveness and post-drying treatments also affect σi; an aggressive drying schedule followed by conditioning remarkably reduces σi occurrence.

The use of isothermal calorimetry to measure corrosion rates of metals in contact with preservative-treated wood

The purpose of this paper is to examine whether isothermal microcalorimetry can be used to determine the corrosion rates of metals embedded in wood. Metal fasteners were driven into dowels of wood treated with alkaline copper quaternary, a common wood preservative that increases the corrosiveness of wood. The dowels were stored in a nearly 100% relative humidity environment at 27°C for one year; throughout the exposure period, dowels were removed and the thermal power generated by the sample was measured in an isothermal calorimeter. Measurements over the 1-year exposure showed that the thermal power depended upon the wood moisture content and ranged from 0 to 200 µW. The heat, determined by integrating thermal power over time, was higher than expected compared with the total amount of mass lost due to corrosion at the end of the experiment. Despite this, the technique shows promise as a method to determine how changes in wood moisture content affect the corrosion rates of metals in contact with preservative treated wood.

Influence of the External Environment on the Moisture Spectrum of Norway Spruce (Picea abies (L.) KARST.)

The fluctuation of relative humidity and temperature in the surrounding environments of wood products is an important parameter influencing their mechanical properties. The objective of this study was to investigate the complex relationship between the moisture content and mechanical properties of wood as a critical aspect in the design of durable and reliable structures. Over a period of 669 days, a simulated type of experiment was conducted, during which the moisture content and external temperature were continuously measured in a compact profile of Norway spruce (Picea abies (L.) KARST.). The data were processed using quadratic and cubic models to establish a predictive model. It was found that the quadratic models slightly outperformed the cubic models when considering time lags greater than six days. The final model demonstrated a significant improvement in explaining the variance of the dependent variable compared to the basic model. Based on these findings, it can be concluded that understanding the relationship between the moisture content and temperature of wood samples plays an important role in wood’s efficient use, particularly for timber constructions. This understanding is vital for accurately predicting the mechanical characteristics of wood, which, in turn, contributes to the development of more durable and reliable structures.

Mode I fracture properties of thermally-modified spruce wood (Picea abies) at different moisture contents

ABSTRACT The influence of moisture content and density on fracture properties of unmodified and thermally modified spruce wood (Picea abies) has been investigated. Thermal modification was done at 180 °C, 200 °C, and 230 °C, and samples were conditioned at 20%, 44%, 76%,% and 88% relative humidity. Double cantilever beam specimens with TL and RL orientation were used for testing. The crack length was determined via digital image correlation, and the compliance of the specimen was determined via multiple loading-unloading cycles of the specimen. The strain energy release rate was calculated, which decreased with an increasing degree of modification and increased with increasing wood moisture content. The analysis showed that the strain energy release rate increased more with wood moisture content for unmodified samples, while the dependence of the release rate on moisture was less obvious for modified samples. The strain energy release rate values are higher in the TL orientation than in the RL orientation, while the crack length has no significant influence. The highest strain energy release rate was 0.256 N/mm for the unmodified TL specimens exposed to 88% relative humidity, and the lowest was 0.071 N/mm for the RL orientation of the thermally modified specimens at 230 °C and then exposed to 88% relative humidity. From all measurements, functions were fitted to calculate the strain energy release rate as a function of orientation, degree of modification, moisture content, and density of the spruce wood, which can be used to calculate the strain energy release rate for any combination of the factors studied.

Moisture Content of Fresh Scots Pine Wood in Areas near Damage Caused by Harvester Head Feed Rollers

By damaging bark, mechanized harvesting deprives wood of its natural mechanical barrier. This study concerns the effect of this damage on the changes in moisture content that occur near the damaged areas of Scots pine (Pinus sylvestris L.). This study was carried out using 45 randomly selected 11 m long logged pine stems. Additionally, the effect of bark thickness on the depth of damage was measured. To determine the influence of the location of the damage and bark thickness on the wood moisture near the damaged region, wood samples were collected from two sections. The first was located one meter above the log’s base, while the second was located one meter from the end of the log. Two increment cores were taken by a Pressler borer in each section: one from the damaged wood zone and the second from the undamaged wood zone. The average bark thickness one meter from the base of the log was 11.2 mm, which decreased to 1.8 mm in the samples taken one meter from the top of the log. The average depths of the damage caused by feed roller spikes in the two sections were 3.9 and 3.8 mm, respectively, indicating that there was no significant effect of bark thickness on the depth of the damage. The wood samples collected near the damaged wood zone (DW) had about 13 percent lower moisture content than those taken from the undamaged zone (UDW). This difference was statistically significant. We observed greater mean moisture content closer to the top of the log for both the samples taken near the damaged zone and the samples taken from the undamaged zone. One meter from the base of the log, the moisture content difference between the DW and UDW was 9.8 percentage points, which was statistically insignificant. By contrast, significantly lower moisture content (−16%) was observed in the DW one meter from the top of the log.

Utjecaj sadržaja vode u drvu na strukturnu cjelovitost drva pri dinamičkim opterećenjima

The majority of mechanical wood properties are negatively affected by wood moisture within the hygroscopic range, disregarding the stress relaxation of wood at very low moisture contents (MC). In contrast, the structural integrity and thus the brittleness of wood appears to be positively affected by moisture. This study aimed at examining the effect of wood MC on the structural integrity of wood between the oven-dry state and MC well above cell wall saturation (CWS), i.e., at approx. 100 %. For both softwood (Picea abies) and hardwoods (Fagus sylvatica and Quercus robur), the structural integrity was assessed on the basis of the Resistance to Impact Milling (RIM) originating from High-Energy Multiple Impact (HEMI) tests. RIM increased with increasing MC in the hygroscopic range, which might be explained by stress relaxation and ‘gluing effects’ inside the cell wall polymer structure, resulting from a growing network of hydrogen bonds on cell wall level. Increasing MC above CWS caused a slight decrease of RIM in the selected hardwood species, whereas no significant change in RIM was observed when MC varied in the range from CWS to approx. 100 % for the softwood species Norway spruce.