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Soft rot decay in acetylated wood. Chemical and anatomical changes in decayed wood
2002 - IRG/WP 02-40231
Acetylated Beech (Fagus sylvatica) and Scots Pine (Pinus sylvestris) wood were studied in soil beds under laboratory conditions for longer periods. High mass losses and dynamic MOE losses were measured in non-acetylated wood and at lower weight percent gains (WPG). Rapid losses of lignin, holocellulose and ?-cellulose occurred in non-acetylated beech wood and no losses were detected at the highest WPG. Changes in chemical composition of acetylated beech wood at lower WPGs was measured. Slight changes in chemical composition of non-acetylated Scots pine wood were also observed and minor changes in acetylated wood at all WPGs; except in holocellulose. An intensive anatomical study was performed by light microscopy and SEM microscopy. The results are presented and discussed. Results showed a significant prevention of acetylation against fungal growth above 8 % and 10 % WPGs in beech and pine respectively.
B Mohebby, H Militz


Strength loss associated with steam conditioning and boron treatment of radiata pine framing
1987 - IRG/WP 3438
The combined effect of included defects and wood moisture content on the strength loss of second rotation radiata pine framing following conventional steam conditioning is investigated. The green Modulus of Elasticity (MOE) is reduced by approximately 13% after steaming. When dried after steaming, however, neither the MOE nor MOR is significantly different from unsteamed dried controls.
M J Collins, P Vinden


Some Experiences with Stake Tests at BAM Test Fields and in the BAM Fungus Cellar Part 2: Comparison of Static and Dynamic Moduli of Elasticity (MOE)
2005 - IRG/WP 05-20320
In routine in-ground stake tests of wood preservatives at the BAM test field Horstwalde and in the BAM fungus cellar periodical determinations of both static moduli of elasticity (MOE) on the basis of bending tests and dynamic MOE on the basis of the vibration method were performed as a possible method for the assessment of fungal attack. As expected from other publications, the absolute values of the dynamic MOE were higher than those of the static MOE. With the equation used for the calculation of the dynamic MOE, the differences were greater with larger specimen sizes. Sufficient correlation was observed, regarding the course of both MOE types within the test period. For both types of MOE, wood moisture contents of the stakes above the fibre saturation point were a prerequisite for the comparability of results in succeeding determinations.
M Grinda, S Göller


Natural progression of decay in unrestrained, Southern pine sapwood exposed above ground
1995 - IRG/WP 95-20060
In this study, the natural progression of decay is being monitored in 2.4-m (8-ft) lengths of dimension lumber. The 2.4-m lengths are supported without restraint in a horizontal plane approximately 0.75 m above ground in a partially shaded field plot in southern Mississippi. The lumber is 100% sapwood. Prior to installation in the field, each piece was planed to exactly 38 by 89 mm² (1.5 by 3.5 in²) when conditioned to 10% moisture content. Members were then sorted according to modulus of elasticity (MOE) into groups with equivalent mean and range. Sets were removed at intervals and the distribution of decay was nondestructively monitored by measuring speed-of-sound transmission through the width of each member. Analysis of the patterns of decay within the members permits design of optimum configuration of above-ground test units. Some key points of consideration were the large variation in amount of naturally occurring decay within a similar population of test units, density-dependent differences in rates of decay development, and overlapping members and end effects. Preliminary results indicate that decay does not become universally established simultaneously along the length of the members. Decay is detected first at the ends and with continued exposure, it progresses to locations more distant from the ends. Presumably, this reflects some contribution of wetting of the exposed end grain to early onset of wood decay.
R C De Groot, R J Ross, W Nelson


A dynamic approach to assess the modulus of elasticity in wood decay testing
1998 - IRG/WP 98-20139
In this study, the changes in elastic behaviour and mass losses of different hardwood and softwood species exposed to decay in a laboratory soil tests were assessed. Wood decay was monitored using different assessment methods, namely: mass loss and changes in elastic behaviours (MOE) determination. Elastic changes were determined by static and dynamic methods, for the latter, acoustic technique was applied. The results obtained show a high correlation between dynamic and conventional static bending measurements of test specimens at different stages of wood decay. The non-destructive assessment of modulus of elasticity assessment proved to be a good tool in the prediction of early stages of wood decay.
L Machek, H Militz, R Sierra-Alvarez


Relationship between the bending strength and the degree of termite attacks on western hemlock by Coptotermes formosanus Shiraki
1990 - IRG/WP 1434
For the examination of the relationship between the bending strength and the degree of termite attacks, Western Hemlock (Tsuga heterophylla Sarg.) was used. Sixty specimens (4.5 x 4.5 x 82 cm³) were attacked by termites at the culture room of Coptotermes formosanus Shiraki. The termites were introduced on the central parts (10 cm) of specimens. In the case of the 2 points loading, the bending moment is maximum at these parts. According to the results obtained from this experiment, both the modulus of rupture (MOR) and the modulus of elasticity (MOE) were showed significant against the weight loss (WL) of central parts of the specimens. MOR = 713 - 19.9 WL (n=60, r=-0.73**) MOE = 127800 - 1910 WL (n=60, r=-0.58**)
K Suzuki, T Tanaka


Biodetioration and strength reductions in preservative treated aspen waferboard
1983 - IRG/WP 2195
Experimental aspen waferboards, bonded with liquid or powdered phenol formaldehyde resins and treated by various methods with a wide selection of preservatives, were tested for fungal resistance in accelerated laboratory trials. Mold growth on the surface as well as weight and strength losses due to the actions of decay fungi were determined. Testing of board strength after decay in high and moderate-hazard exposure conditions required modification of decay tests used for solid wood. A range of protection was noted with no preservative system exceeding the efficacy of the inorganic salt formulations. Averaged over all treatments, strength loss and weight loss are well correlated. Field exposures of effective treatments are underway.
E L Schmidt, H J Hall, R O Gertjejansen, R C De Groot


Changes in some important mechanical and physical properties of untreated and treated mining timber after exposure to the conditions of a colliery
1996 - IRG/WP 96-20082
Each of salt treated and untreated mining timber (wedge) pairs with 5x15 cm² cross-section and 155 cm length prepared from Scots pine, Bornmüller's fir and oriental beech was cut in the small standard test specimens to determine changes in some important mechanical and physical properties, 13 month after exposure to the conditions of Kozlu Hard Coal Mines in the depth of 52 m. Thus, the method for determining the effects of decay on structural timber in service were described. Losses in impact bending, static bending and modulus of elasticity, and specific gravity were calculated as a percentage of the values for controls. Furthermore, relations between residual strength values and losses in specific gravity were statistically evaluated. Decreases in impact bending strength of all controls were ranged from 70% to 88%, in static bending strength from 71% to 73%, in modulus of elasticity from 50% to 56% while losses in specific gravity were ranged from 9% to 11%. The strength losses of wedge blocks treated with CCB salts were found between 3% and 6%, and changes in specific gravity were lower than 1%. Brown and white rot decay were determined on softwood and hardwood samples respectively.
A Bobat


Moisture correction for ultrasonic MOE measurements above fibre saturation point in Scots pine sapwood
2006 - IRG/WP 06-20333
There is a high correlation between methods for dynamic modulus of elasticity (MOEdyn) and static modulus of elasticity (MOEstat). MOEdyn methods have been found sensitive to detect early stages of decay and may be seen as an option for non-destructive wood durability testing. As the MOEstat measurements do not change after reaching the fibre saturation point, the uncorrected MOEdyn data from ultrasonic pulse excitation method provides increasing values after fibre saturation. This is due to the effect of free water in the cell lumen on ultrasonic waves. The aim of this study was to make a moisture calibration for the MOEdyn ultrasonic pulse excitation method using Scots pine (Pinus sylvestris L.) sapwood samples. MOE was measured at five different moisture levels. Three different MOE test methods were used: MOEdyn using ultrasound and vibration excitation and the traditional MOEstat. Sound Scots pine sapwood samples treated with two copper-containing wood preservatives and two chitosan solutions were evaluated, using untreated sapwood samples as control. In this study a correction value ("k") was calculated based on data from different moisture levels for water saturated samples using four different wood treatments and control. By measuring MOEdyn ultrasonic at wood moisture contents just below fibre saturation point, a minor effect of incipient water accumulation in the wood matrix was detected. Wood treatments influence the "k" value, and a "k" value needs to be calculated for all wood treatments when measuring MOEdyn ultrasound above fibre saturation. All the three MOE test methods in this study are applicable for all wood moisture levels as long as a "k" value is calculated for MOEdyn ultrasound above fibre saturation.
E Larnøy, G Alfredsen, H Militz


Natural durability of different wood species in above ground applications - Weight and MOE loss
2008 - IRG/WP 08-10667
In Norway, exterior wood structures have traditionally, nearly exclusively been made of untreated Norway spruce (Picea abies (L.) Karst) and pressure treated Scots pine (Pinus sylvestris L.). In recent years there has been a tendency that other wood species, like various Norwegian hardwoods or imported species, have been used in exterior above ground applications, often not surface treated. For several wood species, especially hardwoods, information regarding the durability in use class 3 is limited. Most information given in EN 350 part 2 is based on testing of the heartwood in ground contact. The test procedures for above ground test prescribed in European standards, both laboratory and field tests, have some weaknesses regarding natural durability testing. Hence, some new methods for accelerated above ground testing have been put forward. The main objectives of this project are to evaluate natural durability of Norwegian and some imported wood species for above ground applications, and to study various methods for assessing decay in wood. The project material and methods used in the project, and the results from double layer tests after one year of exposure has earlier been described, Flæte et al. (2006). This paper presents the results of the weight and MOE loss in small samples after about 3 years exposure above ground.
F G Evans, P-O Flæte, G Alfredsen


Measurement of wood decay by dynamic MOE in an accelerated soil contact test
2008 - IRG/WP 08-20390
Current laboratory and field testing of preservatives involves various techniques to determine the extent of fungal attack, including visual inspection, mass loss, and static bending and compression strength measurements. The objective of this study was to compare decay measurement by conventional compression strength versus dynamic MOE, employing small wood stakes in an accelerated laboratory soil-contact wood decay test. The maximum decay was generally observed close to the center of the stake. An average correlation of 0.884 was observed between the average compression and dynamic MOE strength losses.
Gan Li, D D Nicholas, T P Schultz


Evaluation of variables that influence dynamic MOE in wood decay studies
2009 - IRG/WP 09-20409
The effect of wood moisture content (MC) and outdoor exposure of southern pine lap-joint components on dynamic MOE values was investigated. The use of dynamic MOE as a method of measuring progressive biodeterioration of above ground test samples shows promise, but the accuracy of this method for evaluating test samples subjected to fluctuating environmental conditions has not been reported. The results of this study show that fully water saturated samples had consistently lower MOE values than those obtained at lower MC levels. After the MC was reduced from saturation by about 30%, variation in MOE with changes in MC down to the fiber saturation point were minimal. Outdoor exposure of the test samples also influenced the MOE. After an initial period of outdoor exposure, slightly lower MOE values were obtained for all of the test samples. However, subsequent MOE measurements after additional outdoor exposure were fairly consistent and did not show a trend towards either lower or higher values. For some test samples it was not possible to obtain reliable frequency measurements, resulting in their exclusion from the study.
D Nicholas, J Shi, T Schultz


Testing of decay resistance of sapwood and heartwood of thermally modified Scots pine and Norway spruce
2010 - IRG/WP 10-40523
Thermal modification at elevated temperatures changes the chemical, biological and physical properties of wood. One of the main targets of thermal modification is to increase the biological durability and decay resistance of wood. Although the effects of thermal modification on wood have been widely studied, the significance of sapwood and heartwood on the resistance of thermally modified wood has been paid less attention. In this study the effects of thermal modification at four different temperatures (170°C, 190°C, 210°C and 230°C) on resistance against soft- and brown-rot fungi of sapwood and heartwood of Scots pine and Norway spruce were investigated using accelerated laboratory test methods. Natural durability against the soft-rot micro-fungi was determined according to CEN/TS 15083-2 by measuring the mass loss and modulus of elasticity (MOE) loss after an incubation period of 32 weeks. Test material was also exposed to brown-rot fungi Coniophora puteana and Poria placenta essentially according to a mini-decay test using two exposure periods (6 and 10 weeks). On average, the soft-rot and brown-rot tests gave quite similar results. However, the brown-rot test gave slightly better durability classes than the soft-rot test. The untreated heartwood of Scots pine was more durable against decay organisms than the sapwood of Scots pine and the sapwood or heartwood of Norway spruce. The differences between sapwood and heartwood were more significant within pine than within spruce material. The thermal modification significantly increased the decay resistance of all pine and spruce samples. The higher the level of thermal modification, the better biological durability and resistance against decay will be achieved.
H Viitanen, S Metsä-Kortelainen


Effect of an antioxidant on the efficacy of organic wood preservatives in an accelerated soil contact decay test
2012 - IRG/WP 12-30583
In comparison to inorganic wood preservatives, organic biocides in transient carriers are considerably less effective when the treated wood is exposed to soil contact. Various oils are used in some formulations with pentachlorophenol to improve the efficacy. However, use of these oils imparts unacceptable properties to products used in residential applications. Consequently, there is a need to develop additives other than heavy oils that improve the performance of organic biocides as wood preservatives. In this study the possibility of using the benign antioxidant BHT as a non-biocidal additive to improve the performance of wood treated with isothiazolone and azoles was investigated. The treated wood with and without BHT was exposed to unsterile soil and monitored for decay by dynamic MOE. It was found that the efficacy of both preservative systems was enhanced when BHT was added to the formulations. The use of Dynamic MOE to evaluate the progression of wood decay appears to be far superior to visual ratings.
D D Nicholas, J Shi, T P Schultz, L Sites


Testing the durability of timber products above ground using the block-test method – A critical review
2018 - IRG/WP 18-20637
The block-test method for testing the durability of wood and wood products above ground is reviewed critically with respect to practical aspects, moisture loads, corresponding decay development, and the possibilities of assessing test specimens by determining the dynamic modulus of elasticity (MOEdyn) of wood. In total, 36 blocks representing different modifications of the original set-up and a wide range of tested materials has been evaluated. Rates of decay and MOEdyn loss were compared and assessed regarding their feasibility for durability classification. Benefits and shortcomings of the block-test method are discussed.
C Brischke, A Gellerich, H Militz


Durability classification of preservative treated and modified wood
2019 - IRG/WP 19-20659
EN 350 (2016) allows formally to determine durability classes (DC) for wood products and wood-based materials, which was previously only possible for untreated wood in the form of natural durability. In a first study, the University of Goettingen carried out the durability classification of chemically modified (modified with 1,3-dimethylol-4,5-dihydroxyethyleneurea, DMDHEU) and preservative-treated specimens of various hardwoods and softwoods. The objectives of the work were the determination of mass losses caused by basidiomycetes (CEN/TS 15083-1, 2005) and soft rot fungi (CEN/TS 15083-2, 2005) and to classify durability according to EN 350 (2016). The results showed that a durability classification of chemically modified and preservative treated wood is possible. The tests CEN/TS 15083-1 (basidiomycetes) were carried out with the test fungi C. puteana and T. versicolor and showed that the durability classification is based predominantly on the mass losses caused by C. puteana. However, the distribution of the mass loss values is high, especially for DMDHEU modified collectives. Examinations in accordance with CEN/TS 15083-2 have in many cases led to similar classifications as the tests according to CEN/TS 15083 1. The methodology for evaluating the data proposed in EN 350 (2016) needs to be optimized.
S Bollmus, L Bachle, C Brischke, H Militz


Impact of fungal decay on the bending properties of wood
2020 - IRG/WP 20-20671
Wood used outdoors is generally prone to fungal degradation, and its impact on the structural integrity of wood is an immanent factor for service life planning with timber. Wood decayed to very small mass losses can suffer from a significant reduction in mechanical strength and elastic properties. Hence, the latter are preferred indicators to detect decay in wood durability studies. Numerous previous studies suggested, for instance, modulus of elasticity (MOE) measurements for decay detection since they outperform mass loss in terms of sensitivity. However, literature reports on the topic are not always consistent and partly contradictory. Therefore, this study aimed at 1.) comparing different methods for decay detection with respect to their sensitivity to decay and transferability to each other, and at 2.) quantifying the effect of white and brown rot decay on bending properties of wood. Generally, with increasing mass loss (ML) due to fungal decay bending properties were negatively affected, and brown rot caused more severe damage to elasto-mechanical properties than white rot decay. The elasto-mechanical bending properties were more sensitive to fungal decay than ML but suffered from remarkably high variation. Temporal and spatial distribution of decay affected the structural stability of wood, which became manifested in MOE and MOR (modulus of rapture). Particularly, decay pockets and end-grain decay led to significant ML but had little to no effect on bending properties of the specimens. The quality of correlation between auxiliary quantities such as ML and the underlying target properties strongly depends on the experimental set-up. In the study at hand, wood specimens were placed directly on fully developed mycelium and the total specimen volume was subjected to fungal degradation. The transferability of decay assessment data from one method to the other appeared rather limited. The ML, MOE loss and MOR loss data obtained from recent tests should be considered preliminary but may serve to better define limit states which are essential for decay modelling and service life planning.
S Bollmus, P B van Niekerk, C Brischke


Durability of acetylated Radiata pine: Laboratory tests and performance in practice
2020 - IRG/WP 20-40899
Wood acetylation is an established process to enhance biological durability and dimensional stability of lower valuable wood species without the use of biocides. Acetylated Radiata pine (ACCOYA® wood) has been on the market for more than 10 years now, starting in 2007. Numerous lab tests have confirmed the high durability of acetylated Radiata pine. Here, additional data with four Radiata pine assortments of different origin and quality are shown. All tested variants achieved durability class 1 in both the basidiomycete test and soft rot test according to EN 350. Thereby, no significant differences of the durability characteristics between and within the assortments were found, even though different initial wood qualities were used. Since acetylated wood has not been on the market for that long, less is known about the long-term performance in practice although several long-term field tests are running. As a result of an inspection and evaluation of seven Accoya® constructions exposed outdoors in the Netherlands and Germany over a period of 1 to 10 years, the high dimensional stability and durability against wood-destroying fungi could be confirmed. From the perspective of the authors of this study, the results of the investigation confirm the results of standard lab tests and practical experiences, where the durability class 1 "very durable" (EN 350) was determined.
K Jacobs, W Scheiding, B Weiß


Improvements of monitoring the effects of soil organisms on wood in fungal cellar tests
1996 - IRG/WP 96-20093
Accelerated testing the durability of preservative treated timber in a so called "fungal cellar" or "soil-bed" to evaluate its performance in ground contact is widespread practice. In order to obtain a more accurate and reproducible estimate of preservative performance, several institutes, among them the BAM in Berlin, have routinely carried out static bending tests in addition to visual examination. These tests were usually performed with a defined maximum load or deflection path regardless of the remaining degree of elasticity of the test specimens. Recent studies at the BAM revealed that by modifying the method, i.e. by restricting the applied load to the non-destructive interval for each individual test specimen, the calculated modulus of elasticity (MOE) reflect the changing strength properties caused by biological deterioration and allow within a relatively short time valuable predictions on the service life of the treated timber in soil contact.
I Stephan, S Göller, D Rudolph


Moisture content levels and decay of hemlock
1986 - IRG/WP 1287
As a model of decay conditions of wooden members in wooden houses, a decay test was set up in which samples of western hemlock (Tsuga heterophylla) under 4 moisture levels were examined. Each week the samples were weighed and if the weights indicated that their moisture contents were lower than the expected levels, distilled water was added. Every 8 weeks 3 samples from each condition were oven dried at 60°C for 48 hours, up to 48 weeks. After 48 weeks, 3 samples from each condition were oven dried every 16 weeks. The results obtained were as follows: After examining the samples for 96 weeks at 27°C, the mean weight loss of the hemlock samples kept at about 50-100% moisture content level was larger than those of the other levels. If the samples were dried every 8 weeks, the amount of decay in them was not significant. Decay was also not significant in the samples kept at approximately 20-30% moisture content level.
K Suzuki


Summary of development of pile wrappings in Los Angeles Harbour
1987 - IRG/WP 4141
G Horeczko


Loss of preservatives from treated wood during service
1992 - IRG/WP 92-3734
During the 23rd IRG conference in Harrogate the matter of preservative losses from treated wood during service was raised. We were asked to collect information in this field and ask now for help from you. Many tests have been carried out at a laboratory scale to study fixation and leaching from wood treated with different preservatives. Very little, however, is reported on losses of preservatives during service. Since these values are of great relevance regarding environmental impact and the final disposal, reuse or recycling of treated wood, it is of great importance to get as much information as possible on the amount of active ingredients lost during service life. We are convinced there are quite a lot of analytical data and additional information available in many places all over the world. It appears to be rewarding to collect those data and put them together adequately to get an astimate of the losses of the different components based on a broad scale of in service situations. This work will be done as soon as information is available and it is intended to present the results on next IRG meeting.
M-L Edlund, D Rudolph


Effects of acetylation on the dimensional stability and decay resistance of kenaf (Hibiscus cannabinus L.) fiberboard
1996 - IRG/WP 96-40059
The objective of this study was to investigate the influence of the acetylation treated kenaf fiber, Phenol formaldehyde resin content level, and three fungi species on the dimensional stability and decay resistance of high density non wood composition boards. A standard ASTM method was used to evaluate weight loss and thickness change. The linear shrinkage and expansion of each species were also determined. All specimens were exposed to decay chambers for 16 weeks. Test results indicated that most of the main factors significantly influence the thickness, length changes, and decay resistance of the high density kenaf fiberboards.
P Chow, T Harp, R Meimban, J A Youngquist, R M Rowell


Collaborative soft rot tests: PRL tests of Cu/Cr/As preservative using method of Document No: IRG/WP/208
1973 - IRG/WP 223
These tests were undertaken as a preliminary to the next series of collaborative soft rot tests. An interim report has already been presented at Berlin in 1972 as Document No: IRG/WP/211
J K Carey, J G Savory


On Donkioporia expansa (Desm.) Kotl. & Pouzar
1986 - IRG/WP 1285
Donkioporia expansa is found more often in houses than realised until now. Virulence tests according to EN 113 show not only an attack of oak, but also of other hardwoods and even soft-woods.
G Buchwald


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