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Quantitative assessment of field specimens. A proposal for discussion
1980 - IRG/WP 2143
H Friis-Hansen


Biological detoxification processes - A check list for assessments
1998 - IRG/WP 98-50120
The number of scientific publications on the biological purification of preservative treated wood implies that the biological treatment of wood wastes becomes more and more important. But an information about a successful industrial application is almost missing in all cases. Therefore the applicability of the proposed purification processes is often uncertain. The feasability of such a biological process is assessed exemplary on a method developed at the Federal Research Centre for Forestry and Forest Products. After some large scale-up experiments the investigations were finalized in 1997. An industrial application is unlikely although the process worked in the lab-scale. This critical assessment shows, that - under the given legal restrictions of Germany - the process can not compete with other waste management processes. The evaluation includes the amount, availability and suitability of preservative treated wood waste as well as the process itself, the properties of the purified product and its possible use. The aspects taken into account upon the valuation of the BFH-process are drawn up in a check list. This check list might be a guide for assessing other biological processes and pin-point important questions which should be answered before the industrial application starts or before further investigations are initiated.
H Leithoff, R-D Peek


The natural durability assessments of secondary timber species - field trials
1998 - IRG/WP 98-10297
Secondary or 'alternative' hardwood timber species can replace traditional hardwoods and contribute significantly to satisfying the overall demand for hardwoods in the UK timber market. A selection of these 'alternative' hardwoods is currently being tested at BRE-WTC for natural durability both in ground contact (to EN252) at two field sites, and out of ground contact (as L-joints to EN330) at one site. The objective is to provide an assessment of the suitability of each species for future commercial application. Moisture movement has been monitored in the L-joint tenons showing in less durable timbers, such as rubberwood (Hevea brasiliensis), rapid in-depth wetting during rain. Other monitored features of timber failure in out-of-ground exposure, including surface mould, cracking, discoloration and rot, indicate to date clear species-based differences. Comparison of the test timbers, based upon responsiveness to moisture and degree of timber failure, classify calophyllum (Calophyllum spp.), Ghanaian teak (Tectona grandis) and niové (Staudtia stipitata) as most durable and least reactive to moisture. The results to date of the ground contact trials, when compared with archived durability data show that the archive records of ground contact natural durability remain valid, although some modern plantation-grown timbers, such as teak (Tectona grandis), appear less durable than material from virgin forest. The likely value and commercial application of some of the secondary hardwood timbers examined is summarised.
E D Suttie, R J Orsler


Some Experiences with Stake Tests at BAM Test Fields and in the BAM Fungus Cellar Part 1: Comparison of Results of Visual Assessments and Determinations of Static Moduli of Elasticity (MOE)
2005 - IRG/WP 05-20319
With examples of routine in-ground stake tests differences are shown in the performance of wood preservatives at the BAM test fields Lehre and Horstwalde and in the BAM fungus cellar. Signs of attack of micro-organisms were assessed visually according to EN 252. Periodical determinations of static moduli of elasticity (MOE) revealed the influence of the attack on the elastic properties of the wood specimens. The course of visible signs of attack and the residual MOE corresponded sufficiently in the fungus cellar. At comparable decrease rates of the MOE the visible signs of fungal attack developed slower at the test fields than in the fungus cellar. The stake dimensions distinctly influenced the accelerating effect of the fungus cellar.
M Grinda, S Göller


How to win friends and influence the market — Service Life Prediction and performance-based durability assessments of wood products in construction
2006 - IRG/WP 06-20348
Due to direct and implied demands from the market and from e.g. the EU Construction Products Directive, the need to supply service life estimates for building products is growing. For several years, a development of Service Life Prediction (SLP) methodologies has been going on, but the awareness of this development has hitherto reached only a very limited extent in the wood sector. For materials whose degradation in service is governed by not only physical factors but also, and in many cases to a dominating degree, by biological mechanisms, acurate service life estimates are particularly difficult. Still, in order to defend and expand the market for wood products in construction in the long run, it is of great importance that durability assessments are transformed and expressed in ways that are truly useful for specifyers and users. More clearly stated: The needs and the interests of the user should be in focus and should be the actual starting point for development of both products and durability assessment methods. An initiative to bring this discussion to the CEN Committee TC 38 “Durability of wood and wood-based products” has led to the formation of a Task Group, which will further look into the possibilities to incorporate SLP methods in European durability standards. This development has been carried into effect by the establishment in 2004 of a Task Force within the COST Action E 37 “Sustainability through new technologies for enhanced wood durability”. The Task Force has made preliminary work, making inventories of methods for testing and assessment, analysing the purposefulness of these methods, and giving some outlines for a future performance-based system of classification of wood products. The Task Force will give a final report of its work later this year.
F Englund


Further discussion of biological durability assessments of acetylated wood from several European institutes
2006 - IRG/WP 06-40340
In the last decade, interest in the development of wood modification systems has increased in Europe. Alongside several industrial initiatives for heat treatments, there have also been scaling up and pilot plant projects for chemical wood modification. Between 2000-03, the European Commission funded the "Thematic Network on Wood Modification". This paper features a re-evaluation of work undertaken within that project, assessing the performance of acetylated radiate pine. This re-evaluation comes at a time when acetylated radiate pine is due to be commercially launched. This corresponded with one of the key decisions of the Network, in that modified wood should be regarded as a new wood species, and tested accordingly, with particular emphasis on biological durability and dimensional stability.
D Jones, W Homan, F Bongers


Environmental Emission of Wood Preservatives: Interpretation of Data Relevant to BPD Risk Assessments
2009 - IRG/WP 09-50259
The risk assessments for the use of wood preservatives proposed by the OECD and used under the Biocidal Products Directive (BPD) (98/8/EC) require the derivation of leaching rates for active substances. These rates are to be used as input data in to agreed exposure scenarios. The leaching rates can be derived from laboratory testing and from field testing. The relationship between laboratory and field tests has been studied in order to determine the correlation between the two modes of testing. EN84 tests have been used as a method. However, the determination of environmental leaching rates is beyond the scope of this test and it has been found to over-estimate leaching. The OECD guideline 1 (dipping) test has been designed specifically to determine environmental leaching rates from UC3 wood. This paper compares the leaching fluxes derived from OECD guideline 1 dipping tests to those derived from field tests. This allows a comparison of both the magnitude of flux rates and leaching flux profiles derived from the two tests. The magnitudes of the flux rates require the application of correlation factors in order to get agreement; these factors are presented and found to be of the order 5 – 10. The leaching flux profiles are found to be very different when the flux rates are plotted against time. The laboratory test gives an “exponential” profile, i.e. a profile that decreases quite sharply with time and then levels off. The field test produces profiles that are “sawtooth” patterns with time. This “sawtooth” pattern correlates with rainfall. This is in agreement with, and confirms, data previously presented (Baines, 2008). In the present study, however, an alternative method of data analysis is explored. If the field data is normalised according to the amount of rain falling then it is found that the laboratory and field tests produce very similar leaching profiles. Thus, the contrast previously discussed is shown to be an artefact of the method of analysing the data obtained from field tests. This is due to the inherent variability of weather patterns with time that cannot be replicated in the laboratory. If annual average rainfall figures are used, the risk assessments at differing time points can be carried out as assessments at average rainfall amounts. This alternative method of data analysis according to rainfall rather than time suggests a method of analysing the models for OECD risk assessment that can increase their utility.
D G Cantrell


Effect of Coatings on the Durability of Birch and Spruce Plywood. Part 1: Weathering Performance
2010 - IRG/WP 10-40526
Several different coated birch and spruce plywood types were investigated in Finland using outdoor weathering. The weather performance of the tested coated birch plywood was good compared with uncoated birch and spruce plywood. The paint base film coated and painted birch plywood performed well in outdoor testing at VTT's test site. Phenol film coated plywood was sensitive to UV light, but only a little cracking and mould growth was found after several years outdoor weathering. Edge sealing with acrylate paint protected well the plywood specimens during the exposure. Moisture content of coated birch plywood was less variable and it did not exceed the critical level needed for the early development of decay. The overall results clearly show that birch plywood is better substrate for film coatings.
A Nurmi, H Viitanen