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The effect of gamma radiation on selected wood properties
2008 - IRG/WP 08-40394
As an easy, fast, and effective sterilisation method, gamma irradiation changes molecular structures not only in pest’s living cells, but also in wooden cell walls. Radiation-induced depolymerisation causes significant changes in some properties of wood crucial for restoration and for laboratory testing of wood-preservative effectiveness. The influence of gamma radiation concerning total amount of water-soluble carbohydrates (TSC), maximum swelling (aMAX) and resistance to impact milling (RIM) were investigated. Cobalt (60Co) was used as gamma source and Scots pine sapwood (Pinus sylvestris L.) was irradiated with dosages of 30, 90 and 150 kGy. A strong linear correlation between TSC and the radiation dosage was found. Leached irradiated specimens had significantly greater TSC than non-irradiated controls. RIM decreased significantly and linearly with increasing radiation dosage. After leaching, the linearity between these parameters was improved. Gamma radiation had no significant effect on aMAX and the elapsed time after irradiation did not influence aMAX, RIM, and TSC.
R Despot, M Hasan, A O Rapp, C Brischke, C R Welzbacher

Estimating the heat treatment intensity through various properties of thermally modified timber (TMT)
2009 - IRG/WP 09-40459
The suitability of different measures for prediction of the heat treatment intensity was investigated. Therefore, the resistance to impact milling (RIM), the lightness L*, the equilibrium moisture content (EMC), the anti swelling efficiency (ASE) and the total amount of soluble carbohydrates (TSC) of heat treated specimens were correlated with corresponding fungal resistance achieved by heat treatments. Heat treatment temperatures of 180°C, 200°C, 210°C, 220°C, and 240°C for various heat treatment durations from 0.25 to 72 h were applied. The results show, that the decrease in mass (dm) by heat treatments is a suitable measurand to describe the treatment intensity, which is a product out of treatment temperature and duration, where the impact of temperature is predominating the impact of time. The properties examined showed a strong reciprocally proportional relationship with the decrease in mass. Thus different correlations were found for the various treatment temperatures: The higher the temperature applied, the lower was the decrease in mass required for an equivalent improvement of certain wood properties, e.g. biological durability, EMC, and dimensional stability. However, mass loss by Poria placenta correlated well with the resistance to impact milling (RIM), lightness L*, EMC, ASE and TSC of the different heat treated specimens, depending on the heat treatment temperature. Consequently, a reliable estimation of improved fungal resistance of TMT, as well as the quality control of TMT in general, strongly requires certain process information.
C R Welzbacher, C Brischke, A O Rapp

Mechanical strength of wood from the Vasa shipwreck
2008 - IRG/WP 08-20381
Samples from three ancient ship wrecks (Vasa, Elefanten, and Gröne Jägaren) and recent oak samples as reference were examined with regard to mechanical strength using the high-energy multiple impact (HEMI) - test method, which delivers the resistance to impact milling (RIM) of a material. Adoption and optimisation of the test method for the particular sample size of the wooden drilling cores was necessary. After that optimisation the HEMI method proved to be suitable not only for cube like specimen but also for specimens from wooden drilling cores. The RIM of the different wreck samples was partly significantly different from the recent reference material. Low values indicated deterioration of some cores. Interestingly the wooden core with high iron content showed the highest RIM, even significantly higher than that of untreated recent oak.
A O Rapp, C Brischke, C R Welzbacher, T Nilsson, C Björdal

Changes in mechanical and chemical properties of wood exposed outdoors
2014 - IRG/WP 14-20550
The aim of this study was to investigate differences in certain mechanical and chemical properties of three different wood species (common beach (Fagus sylvatica), Norway spruce (Picea abies), and copper-ethanolamine (CuE) impregnated Norway spruce (Picea abies)) that were exposed in use class 3 (CEN, 2006) for periods between 4 and 30 months. The results show, that changes in the investigated mechanical and chemical properties coincide, with first signs of fungal degradation after 12 to 18 months of outdoor exposure.
N Thaler, C Brischke, D Žlindra, V Vek, M Humar

High-energy multiple impact (HEMI)-test – Part 2: A mechanical test for the detection of fungal decay
2006 - IRG/WP 06-20339
The suitability of the high-energy multiple impact (HEMI)-test for detection of early fungal decay was examined. The HEMI – test characterizes the treatment quality of thermally modified wood by stressing the treated material by thousands of impacts of pounding steel balls. This method differentiates between heat treatment intensities, which are expressed by structural changes of the wood. Similar changes of the wood structure are known for wood decayed by fungi. Pine (Pinus sylvestris L.) decayed by brown rot and beech (Fagus sylvatica L.) decayed by white rot were tested. Mass loss caused by fungal decay and the resistance to impact milling (RIM) determined in HEMI-tests were found to be highly correlated. Testing of non-degraded pine, beech, and ash (Fraxinus excelsior L.) showed only marginal effects of wood density on RIM. Furthermore, annual ring angles and RIM of spruce (Picea abies Karst.) were found to be not correlated. Accordingly, the detection of strength reduction of decayed wood is not masked by variations in density and orientation of the annual rings. Previous results showed no adverse effects of weathering on RIM. Thus, the detection of fungal decay with HEMI-tests is feasible, not only for laboratory purposes, but also for wood in outdoor applications, which was already weathered.
C R Welzbacher, C Brischke, A O Rapp

High-energy multiple impact (HEMI)-test – Part 1: A new tool for quality control of thermally modified timber
2006 - IRG/WP 06-20346
Thermal modification processes improve durability and dimensional stability of wood, but the strength properties, especially the dynamic ones, are compromised and need to be considered with respect to industrial quality control. Results from standard dynamic strength testing, such as impact bending tests, suffer from high variability, and therefore require a high number of replicates. To overcome this, a new test method named high-energy multiple impact (HEMI) was developed. In the present paper heat treated beech (Fagus sylvatica L.), spruce (Picea abies Karst.), silver fir (Abies alba Mill.), and larch (Larix decidua Mill.) were investigated. The HEMI method is based on crushing small specimens by thousands of impacts of pounding steel balls in a heavy vibratory mill. The level of destruction was determined by slit sieving and analysing the size distribution of the fragments. We calculated the resistance to impact milling (RIM) based on the mass of the size fractions. RIM showed a linear correlation with the decrease in mass of the wood by the thermal treatment. The HEMI-test method has the following advantages: small number of specimens, short time for specimen preparation, small variances, high reproducibility of the results, and applicability to timber out of service for a subsequent quality control.
C Brischke, A O Rapp, C R Welzbacher

Influence of heat treatment intensity on the structural integrity of 14 timber species
2012 - IRG/WP 12-40586
Thermally modified timber (TMT) is characterized by improved durability and dimensionally stability, but strength properties, especially the dynamic ones, are compromised at the same time. Because dynamic standard tests require high efforts and time, the high-energy multiple impact (HEMI) –test was developed for the fast and reliable characterisation of the structural integrity of TMT, showing a strong correlation of decreasing structural integrity with rising treatment intensity. Since the number of wood species subjected to this test method was limited up to now, 14 soft- and hardwoods were heat treated by ten different treatments at 180 and 220°C and used for determination of the structural integrity. The results showed temperature dependent strong correlations of decreasing structural integrity with increasing intensity for all species tested, pointing to the general applicability of the destructive HEMI-test in the frame of the post production quality control of TMT. In addition, the structural integrity is not affected by density, anatomical macro-defects like drying cracks, growth ring and fibre deflection or weathering impacts, which confirms its usage for implementation within a reliable factory production control to ensure constant product qualities.
C R Welzbacher, C Brischke, G Maier

The effect of preservative treatment on mechanical strength and structural integrity of wood
2015 - IRG/WP 15-30667
The use of wood for demanding construction applications is increasing in Europe. Wooden constructions are frequently designed of susceptible conifer wood, which is endangered by wood decay fungi in wet applications. Therefore in many cases treating wood with preservatives is unavoidable to ensure the desired service life. However, chemical treatment of wood can result in changes of its mechanical properties. There are contradictory results published in literature regarding the influence of the various impregnation agents on relevant mechanical properties. In order to elucidate mechanical properties of impregnated wood, Scots pine (Pinus sylvestris) sapwood and Norway spruce (Picea abies) wood were impregnated with a copper-ethanolamine based system, an aqueous solution of boric acid and a solvent based wood preservative. For comparison, wood samples were impregnated with deionised water. After conditioning, half of the samples were artificially aged according to the EN 84 leaching procedure. Afterwards, samples were oven dried, and their bending and compressive strength in axial and radial direction was determined. In parallel, structural integrity of the samples was determined in High-Energy Multiple Impact (HEMI) tests. The results clearly showed that treatment with wood preservatives does not have significant influence on the mechanical properties, with exception of non-aged copper-ethanolamine and boric acid treated wood that exhibited significantly lower structural integrity of wood. The negative effect on strength and structural integrity was found to be reversible through exposure to liquid water or high relative humidity.
M Humar, D Kržišnik, C Brischke

Impact of decay and blue stain causing fungi on the structural integrity of wood
2009 - IRG/WP 09-10699
The potential influence of diverse decay patterns caused by different brown rot provoking basidiomycetes on the structural integrity of wood was investigated. Additionally the potential impact of blue stain on the structural integrity was examined. Therefore decayed Norway spruce (Picea abies Karst.) specimens representing a wide range of mass loss, caused by four different brown-rot fungi and one white-rot fungus, were applied to a high-energy multiple impact (HEMI) -test series. The relationship between the resistance to impact milling (RIM) and the mass loss by fungal decay could be subdivided in three areas: 1. Prior to measurable mass loss a strength reduction was detectable due to the depolymerisation of wood cell wall components. 2. Between 0 and 25-30% mass loss RIM decreased with increasing mass loss. 3. Above 30% mass loss RIM increased again due to gluing effects of the fungal mycelium. The influence of the different brown rot fungi on the structural integrity of the wood differed slightly, but partly significantly. According to preliminary results blue stain caused by Aureobasidium pullulans and Sydowia polyspora was found to have no significant impact on RIM.
C Brischke, C Welzbacher, T Huckfeldt, F Schuh

Basidiosporogenesis by the white-rot basidiomycetes in vitr
1994 - IRG/WP 94-10081
Basidiospores of all forest-inhabiting basidiomycetes are a primary source of infection causing wood decay. However, most studies evaluating wood preservatives have used mycelia or basidiospores obtained from wild mushrooms. The objective of this study was to demonstrate in vitro methods that promote carpogenesis and basidiosporogenesis by the white-rot basidiomycetes, Schizophyllum commune and Trametes versicolor. After preincubation in the dark at 27°C for three to fifteen days, basidiospores were produced in four to sixteen weeks in basidiomes exposed to light at 12°C. Adequate light exposure, aeration, and low temperature treatment after preincubation are essential for fruiting body of these white-rotting basidiomycetes. Carpogenesis and basidiosporogenesis of Schizophyllum commune is controlled by nitrogen and carbon limitation. However, fruiting body formation in Trametes versicolor was induced by nitrogen limitation. Walset cellulose was found to be the best carboun source for carpogenesis and subsequent basidiosporogenesis. These results demonstrate the feasibility of using various potential inhibitors on basidiospore germination rather than relying on mycelial growth.
S C Croan

Durability of surface preserved wood particle boards submitted to atmospherical influence
1995 - IRG/WP 95-40039
The worldwide problem of the continuously growing deficit of high quality natural wood material has caused the attempts of many research workers to find effective composites such as wood particle boards (WPBs) for replacing the massive wood for constructive purposes, depending on where the boards are exploited - in the open or under a shed, they are submitted to various climatic factors such as heating, drying, moistening, frosting, irradiation, that's why for reaching high atmospheric resistance, it is very important, a durable protection of the WPBs with suitable coatings against the atmospheric influence to be ensured.
L Valcheva

Improvement of some technological and biological properties of poplar wood by impregnation with aqueous macromolecular compounds
1992 - IRG/WP 92-3721
Poplars (Populus spp) belong to the most important tree species in afforestation programs of the Netherlands. Due to their rapid growth, the wood quality is usually low. Therefore, studies were performed to elucidate whether some technological properties and the resistance against fungal attack could be improved by impregnation with water-soluble resins. The results showed that swelling and shrinkage of poplar wood may considerably be reduced by a treatment with certain resins. The anti-shrink efficiency (ASE) strongly depends upon the resin type. An air-curing alkydresin based on polybutadiene and an air-curing acrylate modified alkydresin emulsion caused the best effects. Additions of wood preservatives to the resins further improved the ASE. Some disadvatages of the tested resins may be seen in their leachability with consequent loss of the dimension-stabilizing effects. The resins by themselves don't reveal fungistatic properties but an impregnation of poplar wood with these materials led in all cases to a better durability against Coniophora puteana and Coriolus versicolor. Leaching procedures influenced the durability in various ways. With resin/fungicide combinations, a good resistance against Coriolus versicolor could be reached even after leaching. SEM and EDXA methods were used to localize the resins in the cell walls and lumina and to detect the growth of mycelium in the specimens.
R D Peek, H Militz, J J Kettenis

Properties of hot oil treated wood and the possible chemical reactions between wood and soybean oil during heat treatment
2005 - IRG/WP 05-40304
Thermal treatment with hot oil as the heating media based on the original idea from oil-heat treatment in Germany was investigated. The treatment was mainly carried out at 200ºC and 220ºC for 2 hours and 4 hours, and the wood species were mainly spruce and fir. This paper focuses on the difference between soybean oil and palm oil and the possible chemical reactions between wood and soybean oil. Generally palm oil was slightly better than soybean oil in improving the moisture resistance properties of heat-treated wood. But soybean oil treated wood appeared to have better decay and mould resistance. The mass loss of wood treated in soybean oil at 220ºC for 4 hours was below 20 % after exposure to Gloeophyllum trabeum in a soil block test, so the treated wood can be classified as “Resistant” according to ASTM D 2017 standards. Natural weathering exposure also shows that soybean oil treated wood is more mould resistant than palm oil treated wood. In order to investigate the effects of absorbed oil on the properties of treated wood and the possible reactions between wood and oils, extraction of different vegetable oil treated wood with chloroform and other solvents was carried out. The results suggest that part of the soybean oil could undergo chemical reactions with wood that renders it of low extractability.
Jieying Wang, P A Cooper

Decay and termite durabilities of heat-treated wood
2004 - IRG/WP 04-40272
Decay and termite resistances of Plato-treated timbers were evaluated using a modified JIS decay test method, feeding test in a laboratory scale and a field exposure against Reticulitermes speratus (Kolbe) or Coptotermes formosanus Shiraki. The results showed that no significant decay durability of the treated timbers although mass loss from decay slightly decreased in case of treated timbers. Treated alder and birch were drastically fed by termite in a laboratory scale feeding test. Filed trials also showed the same results as the laboratory scale test.
S Doi, K Hanataa, E Kamonji, Yuuji Miyazaki

Evaluation of impact of CCA-treated wood on the marine environment
1995 - IRG/WP 95-50040-15
This paper reviews the literature relating to the potential of CCA-treated wood to affect the marine environment and outlines the compounds required for a model which could be used to predict the environemental impact of maritime construction using such timber. Marine pilings require high loadings of CCA to provide protection from marine borers. Though loadings of 32-48 kg/m³ provide long-term protection, preservative content is depleted over time. A number of studies have shown that copper migrates from core regions of treated wood towards the surface and that all three elements are lost by leaching. Most studies of leaching rates in seawater indicate a considerably lower rate of leaching of chrome than for the copper and arsenic. The relatively rapid initial rate of leaching appears to tail off to a much lower level within a short period of time. When trying to predict the effect of preservative leachate, the rate of element movement per unit area of longitudinal surface is the key measurement. Leaching from cross-cut surfaces is more rapid, but such surfaces form a very small proportion of total treated surface area in the below-water portions of wooden structures such as wharfs. In the laboratory, leachate has been demonstrated to adversely affect a range of organisms, but under conditions likely to generate unusually high leachate levels. Certain field observations suggest that epibiota on treated wood and benthic organisms in nearby sediments may be adversely affected by leachate where water circulation is limited. Further realistic measurements of leaching rates and a proper understanding of the chemical and biological transformations undergone by leachate on entering the marine environmment are required before a useful predictive model of the environmental impact can be developed.
R M Albuquerque, S M Cragg

Influence of water-borne preservatives on water repellency and the impact of addition of water repellent additives
1992 - IRG/WP 92-3704
The primary goal of a desirable wood preservative system is to effectively control decay fungi and other biodeteriogens in service. The water repellent nature of a given system may play an important role in the protection of wood. In this study, the water repellency of several water-borne preservative systems has been evaluated by measurements of tangential swelling during immersion. The systems include cuprammonium formulations, such as ammoniacal copper carbonate (AC) and ammoniacal copper zinc arsenate (ACZA), ammoniacal copper quat systems (ACQ) and chromated copper arsenate (CCA). The influence of addition of water repellent emulsions into the above systems has also been examined.
L Jin, D M Roberts, A F Preston

The effects of chemical modification on the biological properties of alder and spruce particleboards
2007 - IRG/WP 07-40363
This study is evaluated by measuring the weight loss, and the ability of white and brown-rot fungi to attack unmodified and modified particleboards manufactured using spruce (Picea orientalis (L.) Link.) and alder (Alnus glutinosa) chips. The chips were reacted with acetic, succinic, maleic and phthalic anhydride at constant temperature for 3 hours then, hot pressed at 150 °C by using phenol formaldehyde (PF) resin. Particleboard specimens were subjected to fungal decay resistance tests performed according to EN 113 standard method using the brown-rot fungus, Coniophora puteana and white-rot fungus, Trametes versicolor. Chemical modified boards demonstrated increased durability against decay fungi. Especially acetic and succinic anhydride treatment reduced the weight losses more significantly than others.
Ü C Yildiz, E Dizman, S Yildiz, A Temiz, M Aslan, E D Gezer

Preliminary investigation of biological resistance, water absorption and swelling of thermally compressed pine wood panels
2008 - IRG/WP 08-40396
Wood can be modified by compressive, thermal and chemical treatments. Compression of wood under thermal conditions is resulted in densification of wood. This study evaluated decay and termite resistance of thermally compressed pine wood panels at either 5 or 7 MPa and at either 120 or 150?C for one hour. The process caused increases in density and decreases in thickness of the panels; however, laboratory decay resistance tests using one brown rot fungus and one white rot fungus revealed that thermally compressed wood was not resistance against the fungi tested. More interesting results were found in laboratory termite resistance tests. As pressure and temperature increased up to 7 MPa and 120?C, mass losses in the specimens decreased gradually when compared to control specimens. However, the specimens compressed at 7MPa and 150?C showed higher mass losses in comparison with the specimens compressed at 7 MPa and 120?C. Decay and termite resistance of such materials is still controversial even though density is improved under thermal processing.
Ö Ünsal, S N Kartal, Z Candan, R Arango, C A Clausen, F Green III

Biological resistance of acetylated particleboards exposed to white (Trametes versicolor (and brown (Coniophora puteana) rot fungi
2010 - IRG/WP 10-40534
This research was conducted to investigate the effect of acetylation on bioresistance of particleboard produced from acetylated wood chips of Fagus orientalis exposed to white (Trametes versicolor (and brown (Coniophora puteana) rot fungi. After 12 hours soaking in acetic anhydride, in order to achieve three level of weight gains, 5, 9 and 16%, acetylated particles were heated in an oven at 120 c˚ for 30, 90 and 240 minutes, respectively. Acetylated and nonacetylated (control) boards were produced with 10% melamine urea formaldehyde (based on the oven-dry weight of particles) and pressed. These boards were tested for decay according to EN113 standard method. Results showed that by increasing level of acetylation, bioresistance of boards increases for both white and brown rot. But, this effect is more obvious for white rot. In fact, by increasing the level of acetylation from zero to 16%, the weight loss of white rotted samples was altered from 21.8% to 0.97% and from 36.3% to 1.78% and for brown rotted samples was altered from 32.6% to 11.3% and from 42.9% to 12.8% after 12 and 16 weeks, respectively.
M Ghorbani kokandeh, K Doosthoseini, A N Karimi, B Mohebby, H Asghari

Determination of Izod Impact Strength on Wood: A Suitable Method to Detect Fungal Decay in Protective Effectiveness-Screenings of Wood Preservatives
2012 - IRG/WP 12-20484
For testing a large number of different substances regarding fungicide properties, the reduction of the decay test duration is advantageous. In the present paper the suitability of a method for testing plastics using an impact testing machine was examined. The results clearly show that the fungal attack of European beech by the white-rot fungus Trametes versicolor leads to a decrease of izod impact strength already after an incubation period of 4 weeks.
H Delenk, M Zauer, A Wagenführ

Study on the Effect of Combined Nanosilver-Hygrothermal Treatment on Wood Properties
2012 - IRG/WP 12-40581
In this study, the impregnation process with nanosilver solution, before hygrothermal treatment was carried out to investigate its effect on some physical and mechanical properties of Iranian beech (Fagus orientalis Lipsky) and Russian imported spruce (Picea abies). Wood specimens were impregnated with nanosilver solution (400ppm) in an impregnation tank under pressure of 0.25 Mpa, for 20 minutes. Hygrothermal treatment was carried out at the temperatures of 120, 150 and 180ºC for 1, 3 and hours. One group of specimens was only hygrothermally treated and considered as controls. Values of volumetric swelling after 24 hours soaking in water, bending strength, impact load resistance and compressive strength parallel to the grain were measured. The results showed that by increasing the temperature of hygrothermal treatment volumetric swelling and mechanical properties of specimens were decreased. The duration of treatment has no significant effects on mechanical properties. Also, in wood specimens which were impregnated with nanosilver solution and treated at 180ºC, volumetric swelling were lower than controls, without any significant decrease in mechanical properties. On the whole, it could be said that with nano silver impregnation of wood, hygrothermal treatment can be carried out at higher temperature (180ºC) to achieve better dimensional stability with no more decrease in mechanical properties.
G Rassam, H Reza Taghiyari, A Karimi, B Jamnani, M Ebrahimi

Study on the Effect of Combined Nanosilver-Hygrothermal Treatment on Wood Properties
2012 - IRG/WP 12-40581
In this study, the impregnation process with nanosilver solution, before hygrothermal treatment was carried out to investigate its effect on some physical and mechanical properties of Iranian beech (Fagus orientalis Lipsky) and imported Russian spruce (Picea abies). Wood specimens were impregnated with nanosilver solution (400ppm) in an impregnation tank under pressure of 0.25 Mpa, for 20 minutes. Hygrothermal treatment was carried out at the temperatures of 120, 150 and 180ºC for 1, 3 and 5 hours. One group of specimens was only hygrothermally treated and considered as controls. Values of volumetric swelling after 24 hours soaking in water, bending strength, impact load resistance and compressive strength parallel to the grain were measured. The results showed that by increasing of the hygrothermal treatment temperature, volumetric swelling and mechanical properties of specimens were decreased. The duration of treatment had no significant effect on mechanical properties. Also, in wood specimens which were impregnated with nanosilver solution and treated at 180ºC, volumetric swelling were lower than controls, without any significant decrease in mechanical properties. On the whole, it could be said with nano silver impregnation of wood, hygrothermal treatment can be carried out at higher temperature (180ºC) to achieve better dimensional stability with no more decrease in mechanical properties.
G Rassam, H Reza Taghiyari, A Karimi, B Jamnani, M Ebrahimi

Resistance of heat treated Ash wood under steam pressure: rot fungi, soil micro-organisms and termites
2016 - IRG/WP 16-40724
Thermal modification processes have been developed to increase the biological durability and dimensional stability of wood. The aim of this paper was to study the influence of ThermoWood® treatment intensity on wood decay resistance improvement against soil-inhabiting micro-organisms, brown/white rots and termite’s exposures. All of the tests were carried out in the laboratory with two different complementary research materials. The main research material consisted of Ash (Fraxinus excelsior L.) wood thermally modified at temperatures of 170ºC, 200ºC, 215ºC and 230ºC. The reference materials were untreated Ash, Beech and Pine woods, for each biological test. An agar block test was used to determine the resistance to two brown-rot and two white-rot fungus according to CEN/TS 15083-1 (2005) directives. Durability against soil-inhabiting micro-organisms was determined relating to the CEN/TS 15083-2 (2005) directives, by measuring the Weight Loss, modulus of elasticity (MOE) and Modulus of rupture (MOR) after incubation periods of 24, 32 and 90 weeks. Finally, Reticulitermes santonensis specie was used for the termite’s exposure non choice screening test with a size sample adjustment according to EN 117 (2005) standard directives. Thermal modification increased the biological durability of all samples. However, high thermal modification temperature over 215°C, representing by a wood mass loss (ML %) due to thermal degradation of 20%, was needed to reach resistance against decay comparable with the durability classes of ‘‘durable’’ or ‘‘very durable’’ in the soil bed test. The brown-rot and white-rot tests gave slightly better durability classes than the soil bed test. Whatever heat treatment conditions, thermally modified ash wood was not efficient against termite’s attacks.
K Candelier, S Hannouz, M-F Thévenon, D Guibal, P Gérardin, M Pétrissans, R Collet

Impact of sapwood portions on the durability of adjacent heartwood of Pinus sylvestris, Pseudotsuga menziesii and Quercus robur. Part 1: Laboratory studies
2018 - IRG/WP 18-10922
Sapwood is generally considered as non-durable and assigned to durability class DC 5 according to European standards independent from the wood species. It is commonly agreed that sapwood decays faster than adjacent heartwood, but it is controversially discussed whether sapwood serves as feeder material and thus accelerates onset and progress of decay in more durable heartwood or decays independently from the neighbouring heartwood. Finally, it might even serve as a biological barrier and thus protect adjacent heartwood from decay. Within this study the durability of sapwood and heartwood of Scots pine (Pinus sylvestris), Douglas fir (Pseudotsuga menziesii), and English oak (Quercus robur) were determined in comparison in laboratory decay tests using Coniophora puteana and Trametes versicolor. To examine potential acceleration of heartwood decay in the presence of sapwood specimens with varying sapwood portions were prepared and inoculated for different time intervals. The presence of less durable adjacent sapwood did neither positively nor negatively affect the resistance against fungal attack of Scots pine, Douglas fir, and English oak heartwood under laboratory conditions. Even though the percentage mass loss (%ML) of sapwood increased with reduced sapwood percentages, the %ML and the absolute ML (absML) of all heartwoods remained unaffected after 8, 12, and 16 weeks of incubation. It appears that at least in the presence of well-established fungal mycelium the presence or absence of sapwood does not impact on the fungal resistance of heartwood.
C Brischke, P Homann, A Gellerich

Impact of water holding capacity and moisture content of soil substrates on the moisture content of wood in terrestrial microcosms
2019 - IRG/WP 19-20662
Terrestrial microcosms (TMC) are frequently used for testing the durability of wood and wood-based materials as well as the protective effectiveness of wood preservatives. In contrary to experiments in soil ecology sciences, the experimental set-up is usually rather simple. However, for service life prediction of wood exposed in ground, it is of immanent interest to better understand the different parameters defining the boundary conditions in TMC. This study focussed therefore on the soil-wood-moisture interactions and their potential effect on durability testing in TMC. TMC were prepared from the same compost substrate with varying water holding capacity (WHC) and soil moisture content (MCsoil). Wood specimens were made from English oak, Beech, Douglas fir, and Scots pine sapwood and exposed to in total 48 different TMC and wood moisture content (MCwood) was studied as well as its distribution within the specimens. For this purpose the compost substrate was mixed with sand and turf and its WHC was determined using two methods in comparison, i.e. the ‘Droplet counting method’ and the ‘Cylinder sand bath method’ in which the latter turned out advantageous over the other. MCwood increased generally with rising MCsoil, but WHC was often negatively correlated with MCwood. Instead, the degree of water saturation Ssoil could serve as a more predictive measure for MCwood in soil exposure scenarios. With increasing Ssoil the MCwood increased, but followed wood species-specific curves with differently steep increase and a plateau at Ssoil = 0 %. In addition, Ssoil from which MCwood increased most intensively was found to be wood-species specific and might therefore require further consideration in soil-bed durability testing and service life modelling of wooden components in soil contact.
C Brischke, F L Wegener

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