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A serial exposure technique for estimating probable service life of treated timber
1978 - IRG/WP 2111
This paper briefly describes part of our preliminary work aimed at developing a test procedure that culd be adopted as a standard method. A detailed version of the work has been submitted for formal publication. In both papers, the aim is to promote interest in extended laboratory testing of wood preservatives. It is believed that this work may provide the basis of a laboratory test procedure from which predictions of field performance could be made. The results of the experiment showed that (a) decay of treated blocks increased with successive soil-jar exposure, and (b) the progressive increase in decay was greatest in blocks to the lower retention of CCA.
J A Butcher

Current state of world standardization in the toxicometric methods for testing of wood preservatives
2007 - IRG/WP 07-20354
The paper presents an outline of the history of forming standardized toxicometric methods for testing of wood preservatives in the world during last 100 years. Numerous studies resulted in three main methods which are currently used for official and basis assessment of biocides: - agar-block method in Europe (EN 113); - soil-block method in the USA and Pacific countries (ASTM D 1413); - modified soil-block method in the Russian Federation and the Commonwealth of Independent States (GOST 16712). Further on the paper compares the three methods and presents lines of their global standardization.
J Wazny

Influence of storage on mould susceptibility of wood at relative humidity values lower than 100%
1989 - IRG/WP 1413
It is well known that wood material changes with time because of different environmental influences. The effects of such changes on the subsequent mould susceptibility are less known. In this paper we report on increased mould susceptibility of pine wood after storage. Mould growth was detected by indirect methods.
J Bjurman

Field stake test assessment with the Pilodyn
1980 - IRG/WP 2136
The Pilodyn, which was originally developed to estimate the degree of soft rot in wooden poles, was thought to have potential for giving a quantitative measure of the extent or depth of decay in field test stakes. In the present work a 2-joule Pilodyn with 2.0-mm diameter pin was used in an attempt to limit depth of pin penetration (to 10-15 mm) without reducing scale sensitivity. The results show that this instrument has the potential for evaluating the degree of decay, particularly its depth, in preservative-treated test stakes exposed in "graveyard" test plots. Its major value could be in eliminating observer bias in assessing decay and in quantification of strenght loss. Its greatest application would be in the accurate detection of the depth of superficial decay, particularly in its early stages, and its further progress into test stakes.
M E Hedley, R W Naish

Protection of wood blocks treated with Trichoderma isolates selected on the basis of preliminary agar screening studies
1996 - IRG/WP 96-10154
Previously reported results of agar interaction screening studies for biocontrol agents of wood decay basidiomycetes showed two Trichoderma viride isolates, killed 16 of 19 target fungi (Tucker and Bruce, 1995). Testing of these isolates in wood was required to assess their performance at preventing decay of wood blocks. Standard testing of chemical wood preservatives is used to determine the toxic concentrations of preservative required to protect the wood against decay by basidiomycetes. As no ratified standards for testing biocontrol agents exist, two amended wood block testing standards were used to assess the two most effective Trichoderma isolates selected on the basis of preliminary agar screening studies. An agar based system similar to European Standard EN 113 (1980) and a soil block test based on the AWPA Standard 1413 (1977) were used with Scots pine and Sitka spruce pre treated with Trichoderma. Results indicated that wood blocks treated with Trichoderma isolates (T60) and (T110) were completely protected against decay by all the basidiomycetes tested irrespective of form of inoculum used (spores or mycelium) or timber species. Implications of the results for the use of agar plate interaction studies for screening biocontrol agents for subsequent use in wood block testing are discussed.
E J B Tucker, A Bruce, H J Staines

Comments on leaching in view of accelerated testing
1977 - IRG/WP 294
We developed an accelerated test for leaching at elevated temperatures (75-85°C). This test was used for the examination of 11 preservative formulations containing Cu, Zn and As. The data obtained from these experiments were compared with data on some formulations tested by ASTM standard leaching test. The method consists in making a large surface to volume ratio of wood from a treated block by cutting into sections approx 40 µm thick and in cyclic extracting preservative salt with a total of 250 ml of distilled water at the elevated temeratures for 24 hours. In conclusion, the new accelerated teet proved to be a fast method which provided reproducible dala on the leech-resistance of various inorganic preservatives. The data are comparable with data of traditional leaching tests at room temperature.
J Rak

Determination of fungitoxic value of preservatives in laboratory wood-block tests. Part 1: Standard procedures
1989 - IRG/WP 2326
By applying a modified agar-block method, a comparative analysis was made on the toxic value of the wood preservative CCA against the test fungus Serpula lacrymans. The procedure applied to determine the results accounted for different standards: EN (Toxic limit), ASTM (threshold retention), GOST (threshold retention and protection probability), PN (toxic doses) and JIS (value of efficiency). Despite some procedural differences the results obtained were to a large extent similar.
J Wazny, J D Thornton

Natural Durability Variations of Malaysian Timbers from Sarawak after 26 Years Exposure by Stake Test
2009 - IRG/WP 09-10704
An extensive graveyard stake test site was established in 1977 in Sibu, Sarawak, Malaysia, to evaluate the in-ground durability of 132 Sarawak wood species, mainly hardwoods. Test samples were planted at 100 x 50 cm spacing. Authenticated wood specimens from 3 trees of each of 132 species were processed into 20 replicated outer heartwood (or else undifferentiated heartwood) stakes of 19 x 19 x 457 mm to represent outer heartwood which were planted to a depth of 228 mm and rated at 6 months intervals using a 5-point visual termite or decay rating scale of ASTM D1758 method. The criteria for a wood species natural durability classification was regarded as the moment when the mean visual rating for a sample of replicated outer heartwood stakes was about 7 (moderate degrade) for commercial relevance (rather than zero for total failure as applied by others), after several months (or years) of exposure regarded as the stake service life being subsequently assigned a 4-point natural durability classification among 1 (very durable) to 4 (non-durable) for 132 wood species. The stakes were also continuously rated until destroyed (rating zero) as a technical requirement. Stake service life data collected over 25 years were analyzed with SPSS software. Stakes of many species were destroyed between 5 and 15 years while the outstandingly durable species belian (Eusideroxylon zwageri) was only reduced to a mean rating 7 after 26 years exposure. Among several wood species tested, particularly variations in natural durability between the different species belonging to the red meranti group, yellow and white meranti group, keruing group, selangan batu group, potential plantation species, heavy hardwoods, medium hardwoods, light hardwoods and the softwoods were demonstrated. Judging by the overall population of 2720 outer heartwood stakes (all species), the decay pressure appeared to be considerably higher (ca 74% by 25th year) than termite pressure (<5% by 25th year) at the Sibu test site.
A H H Wong, Ling Wang Choon

Classifying white rot decay resistance of some hardwoods from Sarawak and Peninsular Malaysia and correlations with their tropical in-ground durability
2012 - IRG/WP 12-10788
White rot wood decay under Malaysian (humid tropical) terrestrial conditions pose more serious threats to the in-ground service life of hardwoods than other common fungal decay types. A study is made on decay resistance variation for a total combined list of 30 Peninsular Malaysian and Sarawak timber species (plus 6 exotic reference temperate commercial woods for comparison) using the laboratory soil-block decay test method of ASTM D 2017, challenged with a representative virulent Malaysian white rot Basidiomycete Pycnoporus sanguineus. Results showed that Hevea brasiliensis (rubberwood) suffered the most severe wood decay with average percentage mass loss of 43.9%, and regarded as non-durable. On the other scale, there was expectedly negligible decay of the most durable species Eusideroxylon zwageri (belian) heartwood with mean mass loss of only 0.7 %. The remaining species varies between non-durability and high decay durability, but mainly moderately durable on the American ASTM 2017 and European EN350-1 decay resistance classification scales. The decay test findings were weakly correlated with recent Malaysian stake test results. Comparative variation of the white rot decay resistance among the timber species will augment the existing pool of information on wood quality classifications of some tropical timbers that are currently sought by the international timber trade, as well as detecting promising relatively decay resistant lesser-utilised species, that the international forest products trade may also be inclined to utilize in addition to the traditional commercial Malaysian species that are now in limited supplies.
A H H Wong, J M E Jem, Lai Jiew Kok

Critical moisture levels and mould resistance of five different wood treatments
2013 - IRG/WP 13-30632
Mould resistance of five different treatments were tested using two methods, a recently developed method for the determination of critical moisture levels of building materials (RHcrit), and ASTM D3273-94. The critical moisture level method exposed samples at 22 °C and 98, 92, 86 and 82% relative humidity (RH) for 12 weeks. ASTM D3273-94 was performed at 29 °C and about 95% RH. Treatments containing fungicide had better efficacy against mould growth than treatments/materials without fungicide. Whilst the ASTM method is relatively simple to perform and provides quick results, the critical moisture level method provides valuable information for different treatments and contributes to a more nuanced evaluation of the treatments' mould resistance. The results from the (RHcrit) test and ASTM after 28 days were compared and there was good correlation between the test methods with respect to mould resistance.
G Bok, P Johansson, A Ekstrand Tobin, S Bardage