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Biological Durability of Laminated Veneer Lumber from Durable and Non-Durable Wood Species
2005 - IRG/WP 05-10567
Laminated Veneer Lumber (LVL) was laboratory manufactured using veneers from decay and non decay resistant species in order to evaluate changes in the durability as a result of the LVL manufacturing process, and to test if the mixing of decay resistant species and non decay resistant species can improve durability. Laboratory soil block test and field test were conducted. The durability of solid wood was comparable to that of LVL made using the same species. For LVL made using veneer from durable and non-durable wood species, durability was improved when two faces and one core veneers were from decay resistant species.
P Nzokou, J Zyskowski, S Boury, D P Kamdem


Estimation of service life of durable timber species by accelerated decay test and fungal cellar test
2002 - IRG/WP 02-20249
Many kinds of durable wood species for outdoor uses has been imported from all over the world to Japan. However information on the natural durability of these species is not sufficient to estimate the service life of them in the climate of Japan. Highly durable species such as Jarrh, Teak, Ipe, Ekki, Selangan batu, Red wood, Western red cedar showed no significant percent mass losses by accelerated decay test according to the JIS Z2101, but some of them are degraded during fungal cellar test for 4 years . The decay rating (0:sound to 5:totally decayed) of them after 4 years exposure was 1.0, 2.0, 0.0, 1.0, 0.0, 2.3, 5.0 respectively. This results indicated that the conventional accelerated decay test could not evaluate the natural durability of these highly durable species at all. Solid wood specimens treated with boiling water at 120? for one hour are subjected to the same JIS test, and the obtained percent mass losses of these species are 1.2, 2.9, 1.9, 3.8, 4.7, 17.5, 0.0 % by a brown rot fungus, Fomitopsis palustris, and 17.5, 14.3, 3.3, 8.2, 4.2, 0.0, 18.3 % by a white rot fungus, Trametes versicolor respectively. Pre-treatment of solid wood specimens for removal of heartwood extractives before a accelerated decay test would be an effective way to evaluate the natural durability of highly durable species in a laboratory.
K Yamamoto, I Momohara


Thermal modification of non-durable wood species 1. The PLATO technology: thermal modification of wood
1998 - IRG/WP 98-40123
The PLATO technology is an innovative upgrading technology with low environmental impact, which can be applied to fast grown and non-durable wood species. This technology is based on a thermal modification of solid wood without the addition of chemicals (e.g. preservatives), consisting of a hydrothermal treatment, followed by drying and curing. The PLATO technology results in a substantial improvement of the natural durability and dimensional stability of wood with only a slight reduction in mechanical properties. Applications of thermally modified wood will include areas where a good durability and/or dimensional stability is required, e.g. garden wood and furniture, wooden sheds, canal lining, joinery, window frames, doors, claddings. In 1998/99 the PLATO technology will be commercialised in the Netherlands. In this paper features of the PLATO technology will be discussed, including selection of wood species, the PLATO process and product development, product properties and applications.
M J Boonstra, B F Tjeerdsma, H A C Groeneveld


Comparison of three methods for assessing the in-ground termite resistance of treated timber, durable timber and plastics at sites in Australia, USA and Thailand - First results
1998 - IRG/WP 98-20132
The in-ground resistance of materials to attack by subterranean termites is most commonly assessed with one form or another of the conventional graveyard method, despite the significant shortcomings of this method. In Australia, an alternative method, in which all samples of test materials are placed below-ground, has been in use for more than 10 years. The method provides reliable exposure of samples to prolonged contact by termites and offers a number of other advantages, notably ease of removal and re-installation of specimens, and protection from fires or damage caused by animals and vandalism. We describe a study in which assessments of materials with the below-ground exposure method were compared with the graveyard procedure and a modification of the South African ground contact method. Sites encompassed a range of climatic conditions and termite faunas, subtropics with species of Reticulitermes in Mississippi, USA; humid tropics with a diverse termite fauna dominated by Macrotermitinae (fungus-culturing termites) in SW Thailand; wet and dry tropics with separate trials for the two economically important species, Mastotermes darwiniensis and the mound-building form of Coptotermes acinaciformis, in Northern Australia; and at a semi-arid inland site with a temperate climate in Eastern Australia where the tree-nesting form of Coptotermes acinaciformis is the dominant species. Materials included in the investigation were: CCA- and ACQ-treated Pinus radiata (each at two retentions), a durable timber (bald cypress, Taxodium distichum) and two plastic cable sheathings (nylon and low density polyethylene). This paper provides details of the trial and gives first observations from inspections at three sites after one year of exposure of the materials to termites.
M Lenz, A F Preston, J W Creffield, K J Archer, B M Kard, C Vongkaluang, Y Sornnuwat


The practice of using concrete on wood piling for marine use in Thailand
1982 - IRG/WP 492
The practice of using concrete on wooden poles has been carried on in Thailand for a long time in pile-houses and pier constructions which have been situated in, or partly in the sea. In such instances, the hewed round and/or square-sawn heartwood poles of naturally durable timber species have been coated with concrete of about 5 to 10 cm or more in thickness, and to about 100 cm above the highest tide level. Very durable species such as Xylia kerrii Craib & Hutch., Shorea obtusa Wall., Pentacme suavis A.DC., Hopea odorata Roxb., and Pterocarpus macrocarpus Kurz were used for such poles. They were well air-dried before the application and coated with a special mixture of concrete, which consisted of sand, crushed lime and stone, and cement powder which was used 1-2 times more than the concrete mixture used for general masonry. The performance of these poles treated in this way, as far as could be ascertained from the users, is about 15 to 20 years, or even more in some instances. Unfortunately it has not been possible to obtain exact data on the service life of these concrete-coated poles. Also palm trees have been used in sea-water without any treatment. The palm trees that have been used are Livistona saribus Herr., and Livistona speciesa Kurz. These have been used as piling for anchoring fishing boats to, because of their high elasticity and also as piles for supporting piers. They have given performances of more than 10 years of service. The outer parts of these trees are very strong and naturally durable to marine borer attack, but the inner parts of them are not resistant to decay fungi, although even though their inner parts have become rotted, they have remained strong enough for the above-mentioned purposes of utilization. If these palm trees are treated with suitable preservatives before being put into use, in order to protect them against the decay fungi, their service lives are much greater than those of untreated palms.
B Anuwongse


Severe decay damages of bridges made of ekki (Lophira alata) wood known as a durable species
2000 - IRG/WP 00-10383
Bridges made of ekki (azobe, bongossi, Lophira alata Banks et Gaertn.) timbers were severely decayed only 10 years after the construction possibly caused from no maintenance for the periods. The reason of no maintenance is due to the misunderstandings on wood durability against wood-decaying fungi. Some civil-engineers and architectures understand "durable species" means "absolutely decay-durable species." They recently like to use durable wood species imported from abroad instead of domestic wood treated with preservatives because Japanese policies and civic insistences avoid to use wood preservatives to maintain natural environment and human health. This paper deals with the details of the typical decay damages of wooden bridges.
S Doi, T Sasaki, Y Iijima


Microbial decay in an extremely durable Malaysian hardwood Belian (Eusideroxylon zwageri) - an overview
1997 - IRG/WP 97-10216
The heartwood of Belian (Eusideroxylon zwageri) is highly regarded among the naturally durable Malaysian hardwoods, and is therefore a choice timber for soilcontact use in the humid tropics such as untreated telecommunication poles, fence posts and railway sleepers. The high microbial resistance of the wood is evidenced by the mere superficial degradation observed in some pole samples after 20 years of service in Sarawak, where electron microscopic studies have reported an unusual type of fungal attack in the cell walls of fibres and parenchyma. Additionally such examinations of Belian stakes from Sabah have confirmed the occurrence of widespread tunnelling bacterial attack on the heartwood surfaces. Other typical patterns of fungal or bacterial degradation have not been observed in Belian wood. The information on microbial decay of Belian heartwood available to date is reviewed and patterns of decay illustrated. Limited information is also available on the fungal resistance of the sapwood and termite resistance. The inherent anatomical and chemical characteristics of Belian wood could conceivably explain the observed superficial microbial degradation patterns and the, otherwise, extreme natural immunity to decay of this timber species.
A H H Wong, A P Singh


The high decay resistance in the sapwood of the naturally durable Malaysian hardwood Belian (Eusideroxylon zwageri)
2001 - IRG/WP 01-10410
It has long been assumed that the observed natural durability of the heartwood in certain timbers is perhaps associated with a relatively lower decay susceptibility also of the sapwood of these species. While the heartwood of Belian is reputedly highly decay resistant among the tropical hardwoods of Southeast Asia, laboratory decay tests reported in this paper have also confirmed the high decay resistance of the sapwood of this timber species. The sapwood of Belian is found to be resistant to decay by soft rot (Chaetomium globosum), white rot (Pycnoporus sanguineus & Coriolus versicolor) and brown rot (Poria sp. & Gloeophyllum trabeum) fungi after 12 weeks of decay testing, sustaining <2% mass loss, equivalent to that in its heartwood. The reference sapwood species Rubberwood (Hevea brasiliensis) and the heartwood of Kempas (Koompassia malaccensis) sustained significant mass losses from decay of up to 59% and 17%, respectively. Microscopic observations of Belian sapwood revealed extensive proliferation of extractives in the lumina of various cell types showing a pattern of extractive distribution similar extent to that in the heartwood tissues, although the extent of cell filling by extractives was not quite as high as for the heartwood. It is plausible that the inherent wood extractives deposited in the cells confer the same degree of anti-fungal properties to both the heartwood and sapwood of Belian.
A A H Wong, A P Singh


Thermal modification of non-durable wood species 2. Improved wood properties of thermal treated wood
1998 - IRG/WP 98-40124
Properties of wood treated in a new heat-treatment process called the PLATO-process have been studied. Several wood species have been treated using this new thermal modification process using a range of process conditions (mainly time and temperature). In this study the characteristics of the treated wood were determined using samples from whole planks treated on pilot plant scale. The modified chemical structure of the wood after treatment results in a product with improved properties. The most important properties of wood, strength, dimensional stability and durability, were determined before and after the heat-treatment. The examined wood species showed a minor loss of strength after treatment. The correlation between the hygroscopicity of the treated wood in moist conditions and the dimensional stability has been studied. Depending on the applied process conditions the hygroscopicity of the treated wood decreased. The hygroscopicity was reduced by 40% and the dimensional stability appeared to have an improvement, ranging to 50%. The durability after heat-treatment was substantially improved.
B F Tjeerdsma, M J Boonstra, H Militz


Possible durability transfer from durable to non durable wood species. The study case of teak wood
2001 - IRG/WP 01-10392
Teakwood is well known for its excellent natural durability, mostly due to its high proportion of extracts. Amongst these extracts, quinones, and more precisely some naphtoquinones (such as lapachol) and anthraquinones (such as tectoquinone) appear to play a crucial role in the resistance to wood decay organisms. At a laboratory scale, sawdust from malaysian teak heartwood has been extracted under different temperatures. These extracts, as well as solutions of commercialised lapachol and tectoquinone were used to treat pine sapwood mini blocks. Such treated and leached samples were used for accelerated fungal tests using basidiomycetes. The results have shown that protection against fungi was achieved through these treatments. Nevertheless, laboratory extracts from teakwood and commercial quinones performed differently, arousing then questions on this way of preserving non durable wood species.
M-F Thévenon, C Roussel, J-P Haluk


Laboratory Evaluation of Soft Rot Resistance of Non-Durable Lesser-Known Malaysian Hardwoods
2006 - IRG/WP 06-10582
Resistance of six non-durable lesser-known Malaysian hardwoods, Pulai (Alstonia spp.), Rubberwood (Hevea brasiliensis), Ludai (Sapium spp.), Jelutong (Dyera costulata), Gaham Badak (Blumeodendron tokbrai) and Kayu arang (Diospyros spp.) compared with temperate Scots pine sapwood (Pinus sylvestris), were evaluated using the unsterile soil burial (mixed with Chaetomium globosum) versus vermiculite-burial (of C. globosum only) laboratory techniques and decay rates expressed as either percent mass/mass or percent mass/volume basis. Scots pine was expectedly soft rot resistant but Pulai wood was almost immune to decay. Other wood species varied from being moderately to highly susceptible to soft rot decay. The vermiculite-burial technique favoured greater soft rot degradation activity than unsterile soil-burial. Results also suggest that soft rot decay rates of susceptible woods could also be accelerated with higher surface area/volume ratios of test blocks. The use of mass/volume basis indicated similar reduced degrees of soft rot resistance among most test wood species whereas apparent differences among woods were found using mass/mass comparisons probably due to variable basic densities among these timbers.
A H H Wong


Detection of Anti-Fungal Sapwood Extractives in Non-Durable Scots Pine (Pinus sylvestris), Rubberwood (Hevea brasiliensis) and Jelutong (Dyera costulata)
2007 - IRG/WP 07-10634
A general laboratory bioassay method of Woodward and Pearce (1985) was adopted to detect anti-fungal activity of sapwood or heartwood extractives of 5 Malaysian hardwoods [dark red meranti heartwood (Shorea spp.), red balau heartwood (Shorea spp.), kulim heartwood (Scorodocarpus borneensis), jelutong sapwood (Dyera costulata) and rubberwood sapwood (Hevea brasiliensis), including the temperate Pinus sylvestris (Scots pine sapwood). The heartwoods of these species and Scots pine sapwood are known to be highly resistant to decay by soft-rotting Ascomycetes and anamorphic fungi (about 1-7% wood mass loss), while the sapwoods of rubberwood and jelutong had much reduced soft rot resistance (respectively 35, 32% wood mass loss) but obviously prone to sapstain and mold attack, including that of Scots pine. Crude methanol extracts of woodmeal samples of each wood species were loaded on to thin-layer chromatography plates at between 0.003 and 0.1 g fresh mass equivalent of woodmeal per spot so as to optimize resolution of separated compounds, and developed with chloroform:methanol solvent (ratio 19:1). The dried plates were sprayed with fresh fungal spores of Cladosporium cucumerinum and incubated at >90% RH for 5 days in the dark. Presence of anti-fungal compounds was revealed by white regions along the solvent transect for each extract of each species where inhibited spore germination and mycelial growth of C. cucumerinum occurred. Comparisons of anti-fungal activity of extracts between species and between sapwood and heartwood were made. Results revealed that several zones of inhibitory activity, indicated by their Rf-values, were clearly visible on chromatographic separations of methanol extracts of these 5 wood species. The inhibitory zones for 2 heartwood extracts (except kulim) did not move from the origin which was also resistant to infection. However inhibition zones were also detected for the sapwoods of rubberwood, jelutong and Scots pine against C. cucumerinum despite the known sapstain and decay susceptibility of these wood substrates. The presence of hitherto unidentified anti-fungal compounds in the sapwoods of these species may elicit limited potency or narrow spectrum protection from fungal infection and onset of stain or decay.
A H H Wong, R B Pearce


Feasibility study on three furfurylated non-durable tropical wood species evaluated for resistance to brown, white and soft rot fungi
2008 - IRG/WP 08-40395
Furfurylation can protect non-durable wood species against biological degradation, but the method used today cannot fully protect the heartwood of Scots pine due to insufficient penetration. In order to test alternative wood substrates for furfurylation, three Malaysian grown wood species (Kelempayan, Rubberwood and Sena) were furfurylated and subjected to soil block decay testing. Their performance was compared to furfurylated Scots pine and furfurylated Beech modified using the same process. In addition, treatment characteristics were evaluated. One of the species tested, Kelempayan, seems to be a promising substrate for furfurylation. Kelempayan is easy to impregnate in both sap- and heartwood, and a 50% higher weight gain was reached using equivalent amounts of impregnation solution compared to Scots pine. Sena, Rubberwood and Beech returned weight gains 40-60% lower than Scots pine. Decay protection was largely comparable at equivalent weight percent gains for all wood species tested, although differences appeared. Generally, a weight gain of approximately 25% by furfurylation seems to offer good protection in the chosen soil block test.
T Mark Venås, A H H Wong


Field Tests of naturally Durable North American Wood Species
2008 - IRG/WP 08-10675
There has been little field test performance data published on North American naturally durable species in general, and no published data on second growth material in particular. Yellow cedar (Callitropsis nootkatensis), western red cedar (Thuja plicata), eastern white cedar (Thuja occidentalis), and three wood species reputed to be moderately durable were installed in ground-contact (stakes) and above-ground (decking) field tests at test sites in British Columbia and Ontario, Canada and Florida and Hawaii, USA between the Fall of 2004 and Spring 2005. Where possible old growth and second growth material, with and without sapwood, were obtained and used in the testing. Results from ground-contact field stakes and above-ground mini-decks after 3 years exposure are presented. The test site with the fastest ground-contact decay rate was Florida. The fastest above-ground decay rate was seen in Hawaii. In general, yellow cedar was the most decay resistant, followed by the other two cedar species, then the three other species. There was no appreciable difference in decay resistance between heartwood samples from old-growth and second-growth western red cedar, yellow cedar, and larch (Larix occidentalis).
P E Laks, P I Morris, G M Larkin, J K Ingram


Ensure Durable Wood-Frame Construction under the Climate and Biological Hazards in Shanghai
2009 - IRG/WP 09-20413
This paper provides technical background for developing durability-related provisions for the Shanghai wood-frame construction code. It summarizes the related climate, decay and termite hazards in this area as well as traditional durability solutions used for wood and wood hybrid constructions in China. The overall durability principles or philosophy used throughout this durability chapter are to improve and ensure building durability using integrated protection methods by appropriate design and construction and by using preservative-treated or naturally durable wood where necessary. Of these principles, durability by design is taken as the most fundamental approach for achieving good long-term performance of a building as a whole, and using durable wood where necessary to ensure the durability of individual components. This chapter covers moisture and termite management, and whenever possible multiple lines of defence are provided. Meanwhile, the practical side is also taken into consideration in order to make sure that all measures are buildable on construction sites with a reasonable cost.
Jieying Wang, Chun Ni, Jiahua Zhang


Above Ground Field Evaluation and GC-MS Analysis of Naturally Durable Wood Species
2012 - IRG/WP 12-10764
Nine wood species are being evaluated in above ground field studies in Mississippi and Wisconsin. Candidate naturally durable wood (NDW) species are being rated at yearly intervals for resistance to decay, cupping, and checking. Field ratings after 12 months exposure are presented. To date, Paulownia tomentosa (PAW) and southern yellow pine (SYP) are least durable and cedars are the most durable in above ground exposure. Wood samples are being taken from the deck-boards and subjected to chemical analysis using GC-MS. Fatty acids from NDW species were extracted, derivatized, and analyzed along with commercial fatty acid methyl ester (FAME) standards. With few exceptions, results indicate that FAMEs are more abundant in NDW species. However, preliminary bioassays found no inhibition of select wood decay fungi by FAMEs at naturally occurring concentrations.
G T Kirker, A B Blodgett, S T Lebow, C A Clausen


Use of the durable species Coast Redwood as a reference system for field testing of Wood Protection systems
2012 - IRG/WP 12-20486
Data is provided and discussed for a number of field exposure tests where the naturally durable wood species Coast redwood, Sequoia sempervirens, was included along with untreated pine and standard preservative treatments. In general, there is potential for higher variability of results with this naturally durable species, but it does suggest that redwood can be a useful reference material for testing systems for above ground applications, especially where long-term decay performance may not be as critical as overall product quality. Comparative performance of products to redwood heartwood at test sites with different climate indices and with different test methods may provide additional useful data on the relative performance of systems than when compared to only untreated pine sapwood and standardized preservative systems.
A Zahora, A Preston, L Jin


Transferable Durability: Enhancing decay resistance of non-durable species with extractives from durable wood species
2013 - IRG/WP 13-10808
Extractive content and composition is a vital component of naturally durable woods; however, variability in extractives can limit their usefulness in the field. Two extractive-free, non-durable wood species were pressure treated with ethanol-toluene extractives from 8 durable wood species. Extracted Southern pine, Paulownia and unextracted Southern pine blocks were treated and challenged in soil bottle experiments with four common wood decay fungi. Weight loss from fungal degradation of the extractive-treated blocks was compared to untreated controls. Results indicated that in some cases, treatment with extracts from durable wood species decreased the percent weight loss from exposure to decay fungi. Chemical analysis of extractives from these durable and non-durable woods was performed using GC-MS and chemical components were compared. Several unique compounds were found in the more durable species compared to less durable species.
G T Kirker, A B Blodgett, S Lebow, C A Clausen


Microbial Community Analysis of Naturally Durable Wood in an Above Ground Field Test
2014 - IRG/WP 14-10826
This paper presents preliminary results of an above ground field test wherein eight naturally durable wood species were exposed concurrently at two sites in North America. Surface samples were taken at regular intervals from non-durable controls and compared to their more durable counterparts. Terminal Restriction Fragment Length Polymorphism was performed to characterize the microbial (bacteria, fungi, and basidiomycetes) communities present. Differences were noted among wood species and seasonal shifts in microbial diversity were noted at both sites. Attempts to correlate diversity indices with decay ratings were unsuccessful, but differences in species richness were noted for several of the naturally durable species. Western red cedar had significantly fewer bacterial species compared to other wood species. Fungal and basidiomycete species richness differed due to site and fungal species richness increased with increased exposure. Clustering of fungal and basidiomycete communities suggests seasonal patterns of colonization at both sites, but was more defined in the more southern site; Saucier, MS (MS). Future analyses will focus on comparison of years to model successional patterns of bacteria, fungi, and basidiomycetes.
G T Kirker, S V Diehl, P K Lebow


Unexpected natural decay resistance strategies of durable tropical woods Bocoa prouacencis, Vouacapoua americana, Inga alba and relationship with specific gravity and wood extractives
2014 - IRG/WP 14-10832
The study of decay resistance in wood is of interest for wood end-users but also for the global carbon balance since wood biodegradation is a key driver of forest ecosystem functioning through its impacts on carbon and nutrient cycling. We studied the specific gravity and wood extractive contents in order to understand decay resistance against soil microflora after 90 days exposure of sapwood and heartwood from three Neotropical wood species known for their decay resistance: Bocoa prouacencis, Vouacapoua americana, Inga alba and Virola michelii. Decay resistance was correlated with specific gravity more than wood extractive content. The results highlighted different decay resistance strategies. In Bocoa prouacencis, both sapwood and heartwood were highly resistant due to the high specific gravity and the antifungal wood extractive. In Vouacapoua americana heartwood, decay resistance was due to the high synergistic-acting wood extractive content. Conversely, with the least dense wood species Inga alba, we found that decay resistance was due to the antifungal wood extractives synthesized early in the sapwood. In conclusion, we showed that the three wood species with the same level of heartwood decay resistance performance had different decay resistance strategies according to the anatomic and defensive wood traits.
N Amusant, M Migg, B Thibaut, J Beauchene


GC-MS Characterizations of Termiticidal Heartwood Extractives from Wood Species Utilized in Pakistan
2016 - IRG/WP 16-10857
Wood species that exhibit innate tolerance to wood destroying organisms such as termites are considered to be naturally durable. This durability can, in part, be due to the complex chemical compounds in the heartwood of naturally durable wood species. We examined the effects of varying concentrations of heartwood extractives on the subterranean termite, Reticulitermes flavipes from four wood species from Pakistan (Dalbergia sissoo, Cedrus deodara, Morus alba and Pinus roxburghii) as well as Teak (Tectona grandis). Termites showed increasing levels of mortality with increasing concentration of heartwood extractive when exposed to extractive treated non-durable southern yellow pine (SYP) blocks in a force feeding test compared to SYP blocks treated with water or solvent (ethanol: toluene) only. Characterizations of heartwood extractives were performed using Gas Chromatography-Mass spectrometry (GC-MS). Chemical profiles were prepared for each wood species’ extractives and are discussed relevant to their termiticidal properties. Future work will focus on further isolation of bioactive compounds or synergistic groupages of bioactive compounds from these and other wood species for use as environmentally friendly insecticides/termiticides for wood and wood based materials.
M E Mankowski, B Boyd, B Hassan, G T Kirker


Laboratory evaluations of woods from Pakistan and their extractives against Postia placenta and Trametes versicolor
2016 - M Mankowski, B Hassan, A Bishell, G Kirker
Natural durable wood species are those which exhibit innate tolerance to wood decay organisms such as fungi and termites. The goal of this study was to evaluate 4 wood species (Dalbergia sissoo, Cedrus deodara, Morus alba and Pinus roxburghii) from Pakistan in order to determine their resistance to both a model brown (Postia placenta) and white (Trametes versicolor) rot fungus compared to a durable reference species (Tectonis grandis). In a 12 week soil bottle test, C. deodara and M. alba were found to be resistant to decay, D. sissoo was moderately resistant and P. roxbughii was non-resistant. This resistance was greatly reduced when blocks were leached with a series of solvents. When a non-durable species was treated with extractives from these species, decay resistance did not improve against either brown or white rot test fungi.
M Mankowski, B Hassan, A Bishell, G Kirker


Coula edulis baill an unknown wood species as an alternative to the main durable wood species used in Gabon
2019 - IRG/WP 19-10945
The Congo Basin hosts an exceptional biodiversity of trees, flora and fauna. However, the immense natural heritage of the forests in this area is increasingly threatened by many anthropogenic factors, due to selective exploitation of certain wood species. In Gabon, whose ecosystem is representative of this area, the forest represents nearly 80% of the national territory. Only a minority of wood species is exploited because of their high market value (Ageos, 2015). The direct consequences of this selective exploitation are the decrease of the disponibility and even the eventual disappearance of certain wood species associated to the fast-growing international tropical timber markets. This is the case for kevazingo, which is classified as an endangered species and therefore prohibited from exploitation. In addition to these main exploited species, several less known species are available in Gabon. This is the case of the Gabonese hazelnut tree (Coula edulis baill), whose wood is used by local populations for its longevity because of its resistance to fungi, insects and more particularly termites. It is used to make forge coal and is used in the construction of huts such as posts and lintels (Moupela C et al, 2010-2013). In this context, it seemed interesting to study more in detail this species, having for the moment been the subject of little scientific investigations. The aim of this study was to investigate the natural durability of Coula edulis and the reasons of this latter one based on wood chemical composition. For this purpose, durability tests were carried out in Petri dishes on native and extracted samples of heartwood towards brown rot (Poria placenta and Coniophora puteana) and white rot (Coriolus versicolor and Pycnoporus sanguineus) fungi showing that unextracted samples presented higher durability to fungi. Fungal growth inhibition tests carried out with different concentrations of extractives confirmed their important fungicidal effects. Percentage of the different wood polymers and chemical composition of wood extractives were evaluated to find correlation between durability and wood chemistry. Results indicated that natural durability of Coula edulis could be explained by several reasons like the high density and hydrophobicity of its wood as well as its high lignin and extractives contents. Chemical analysis performed on extractives by GC-MS indicated the presence of gallic acid, quercetin and tannins.
C S A Bopenga Bopenga, S Dumarçay, P Edou Engonga, P Gerardin


Future development of durability assessment of wood, according to typical usage of preservative-treated wood and naturally durable wood in Japan
2020 - IRG/WP 20-20675
A market of preserved wood products in Japan has two unique histories. First is the market shift to residential ground sills from utility poles and sleepers; the other is the stop of CCA treatment caused by the new effluent standard. In 2018, around 85% of preserved wood products used for residential ground sills were treated with non-CCA such as Cu-based agents. Since the market of treated wood has been so low in Japan, various types of durability evaluation methods were not needed. The in-ground field test is the only standard test in Japan. On the other hand, the exterior use of wood above ground, such as decks and cladding, is expected as a new market of treated wood. As above-ground conditions are different from in-ground, a lot of field tests for the above-ground has been conducted throughout the world. A new field test is also needed in Japan to evaluate the durability of wood products. This paper reports on the current status of durability standards in Japan, and the recent studies and future developments of durability assessment for above-ground use in Japan.
T Osawa, W Ohmura, H Kurisaki


Service trial of different materials exposed in jetties at Öresund. Progress report No. 5
2022 - IRG/WP 22-30764
This report contains results of the fifth inspection on the performance of different decking materials – preservative-treated wood, modified wood, natural durable wood, re-cycled plastics and wood-plastic composites (WPCs) - available on the market and exposed since 2013 (some since 2014 and 2016) by the City of Malmö in two jetties near the Øresund Bridge, south of central Malmö in Sweden. The objective of the test is to gather information on performance with respect to appearance, durability and function of the tested materials. The test has, in spite of the relatively short exposure time, provided useful information on the properties of the different materials and their suitability for outdoor end-uses exposed to severe conditions. The colours of all wood materials quickly became greyish, whereas the colour of the WPCs and re-cycled plastics remains roughly the same as the original, although somewhat faded, after approximately 101 months’ exposure. All materials apart from the re-cycled plastics have been more or less attacked by disfiguring fungi or algae, and in some cases by lichen as well. Decay was found in one plank of Organowood silica-modified wood after approximately 65 months’ exposure, and after another 12 months all Organowood planks were attacked by decay, which has further developed since. The decay is very likely caused by poor efficacy of the silica-based product. Incipient decay has also been found in Europen oak, black locust/robinia, roble, Kebony (one little spot only) and in one plank of Scots pine heartwood, superficially treated with Sioo, another silica-based product. The mechanical properties vary considerably between the materials. Planks of European oak, black locust/robinia and roble have all been subject to checks, edge fractures and splinters. The use of these materials for jetties, boardwalks and decking where injuries to bare feet is a risk, should be avoided. Grooved material of bangkirai, azobé and Thermowood seems susceptible to more mechanical influence than non-grooved material.
J Jermer


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