IRG Documents Database and Compendium


Search and Download IRG Documents:



Between and , sort by


Displaying your search results

Your search resulted in 19 documents.


Ekki heartwood - is “Durable”
2002 - IRG/WP 02-10444
Severe decay damages of bridges made of ekki (Lophira alata Banks) wood which is classified as a durable species in the EN 350:2 as already reported at the 31 IRG annual meeting. This paper deals with results of long-term decay tests of ekki heartwood specimens using 3 isolates (Loweporus tephroporus 2 strains and a fungus of other sp. from damaged ekki bridges) and Trametes versicolor as a reference. Sound ekki heartwood specimens, sized 20(T) x 20(R) x 5(L) mm were used. References were Japanese beech (Fagus crenata) specimens having the same dimensions. Oven dry weights of the specimens were measured at 60 oC for 48 h before and after the decay process. Nine replications of specimens were used per set. The procedure of decay test was about the same as that of the JIS Z 2101. All the test fungi including T versicolor decayed ekki heartwood in the case of long-term exposure (more than 6 months) using the appropriate nutritional condition under optimum temperatures. These facts suggest that the results of standardised decay test methods should be carefully interpreted.
S Doi, R Itoh, S Horisawa


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


Laboratory culturing and decay testing with Physisporinus vitreus and Donkioporia expansa orginating from identical cooling tower environments show major differences
1996 - IRG/WP 96-10184
Both Basidiomycete fungi Physisporinus vitreus (Pers.:Fr.) P. Karst. and Donkioporia expansa (Desm.) Kotl. & Pouz. were isolated from identical cooling tower environments. Azobé heartwood (Lophira alata), a very durable tropical wood species was totally deteriorated in cooling towers in a similar way by both fungi. First attempts to culture Physisporinus vitreus in laboratory circumstances showed a need for climatic conditions with higher temperatures and higher relative humidity compared to standard conditions known for most Basidiomycete fungi. Moreover there is a supplementary need to alter the acidity of the malt-agar medium and to add a protein nitrogen source like pepton. Identical culturing conditions were supposed for the Donkioporia expansa isolate. However the alteration in acidity is not beneficial for the growth of this cooling tower fungus. High mass loss figures up to 50% were recorded for non-durable wood species inducing wood moisture contents of over 150%, but only a slight growth stimulation on azobé could be observed under laboratory conditions.
J Van Acker, M Stevens


Highly virulent wood-rotting Basidiomycetes in cooling tower timbers
1995 - IRG/WP 95-10125
Over the past ten years most industrial cooling towers changed their water treatment systems in order to meet environmental requirements. Since this alterations wood rot attack has been reported more frequently. Several Basidiomycete fungi were isolated and determined. Amongst the most important ones are strains of Physisporinus vitreus (Pers.:Fr.) P. Karst., Phellinus contiguus (Fr.) Pat. and Donkioporia expansa (Desm.) Kotl. & Pouz.. In situ total deterioration has been reported of highly durable wood species like azobe (Lophira alata), bangkirai (Shorea leavis) and Californian redwood (Seqouia sempervirens) and of CCA-treated softwood, e.g. Douglas fir. The Donkioporia strain was only recently isolated while on lab-scale research is ongoing to stimulate the growth of Phellinus. The growth under laboratory conditions is not evident for these fungi and different parameters affecting growth were investigated. After altering the malt-agar as medium and improving climatic conditions fungal growth of Physisporinus in laboratory conditions on durable wood has been succesful already. Some preliminary results related to the changes in water treatment are discussed.
J Van Acker, M Stevens, V Rijckaert


4th Report on condition of panels at Sekondi, Ghana
1978 - IRG/WP 445
F F K Ampong


Laboratory tests on the natural durability of timber methods and problems
1984 - IRG/WP 2217
In literature a large variety of test methods is mentioned to examine the natural resistance of timber against fungal attack. This concerns the kind of sampling as well as the test procedure, the test fungi, the duration of test, and the classification of the resistance according to the test results. These variations, however, are of great influence on the test result. Long term exposure will lead to a further differentiation of timber species to be generally known as "resistant".
H Willeitner


Field tests of different tropical wood species in sea water
2022 - IRG/WP 22-30773
A number of tropical timbers have been tested according to EN 275 at Kristineberg Marine Research Station in Sweden since 1999. Most of these tests have started during the last 5-8 years. Wood species included have been Lophira alata (Azobé/Ekki), Minquartia guianensis (Manwood/Acaria), Chlorocardium rodiei (Greenheart), Cyclodiscus gabonensis (Okan/Denya), Shorea spp. (Bankirai), Dicorynia guianensis (Basralocus/Angélique), Tectona grandis (Teak) and Handroanthus spp. (Ipé). Only one of the wood species included have shown to be highly resistant to marine borer attack, Manwood/Acaria, which is also the wood specie that performed best in a marine test in Portugal (Williams et al. 2007). The test group of Manwood/Acaria is still rated “sound” after 22 years in our test. The performance of the other species is surprisingly poor with e.g., average life (time to failure due to shipworm attack) of only 3.8 years for both Greenheart and Okan/Denya. This seems to be in line with speculations about increased borer activity on the Swedish West coast causing increased shipworm attack on harbour constructions of tropical wood, mainly Azobé. In our test Azobé got an overall rating of “Failure” after 8 years in test.
M Westin, P Larsson Brelid


Water-based water repellents for treatment of wood
1987 - IRG/WP 3446
The water uptake by wood can be reduced by treatment with a water repellent. The water repellents most commonly used are solvent based. In the present work a new type of water repellent that is water-based has been investigated. Two different treatments have shown an effect of the same order as a commercial solvent based product. The cellular distribution of the water repellents has been investigated and for one of the formulations a more uniform distribution can be seen at the impregnated surface. Use of water as a solvent would be advantageous due to lower cost and non-toxicity.
I G Svensson, G Hägglund, I Johansson, W B Banks


Copper binding capacity of modified wood flour
1992 - IRG/WP 92-3709
Wood flour was modified by reaction with oxidising agents and CCA preservative. The copper chromium and arsenic were removed from the CCA treated wood flour by an acid leaching procedure. The modified wood flours were allowed to react with copper acetate solution and the level of copper fixation achieved was determined. The modified wood flours had greater affinity for copper ions present in solution than unmodified wood flour.
N C Milowych, W B Banks, J A Cornfield


The colonization of selected naturally durable timbers by marine fungi and borers
1977 - IRG/WP 439
In recent years, concrete and metal have been widely substituted for wood in contact with sea water, but wood products have not lost their usefulness under such conditions. In many cases, wood if sound and durable, may prove to be the most practical and economical of materials used in sea water exposure. Timber when immersed in the sea may be attacked by micro-organisms (bacteria and fungi) and marine borers (members of the molluscan genera: Teredo, Psiloteredo, Lyrodus, Bankia, Pholas, Martesia and others, also members of the crustacean genera: Limnoria, Paralimnoria, Sphaeaeroma and Chelura). Although marine borer damage is the more dramatic, damage by marine micro-organisms can contribute to cause soft rot of wood (Jones and Byrne, 1976), and they are also believed to be implicated in the 'preconditioning' of a wood surface prior to settlement of marine borer larvae (Eltringham, 1971). Ten tropical timbers (Mukulungu = Autranella congolensis, Moabi = Baillonella toxisperme, Angelique = Dicorynia guianensis, Jarrah = Eucalyptus marginata, Congotali = Letestua durissima, Azobe or Ekke = Lophira alata, Bilinga or Opepe = Sarcocephalus diderrichii, Douka = Tieghemella africana, Makore or Baku = Tieghemella heckelii, Wacapou or Acapu = Vouacapoua americana) were choosen to examine their natural durability in sea water in Italy, France, Ghana and Canada.
S E J Furtado, E B G Jones


Paper for discussion - Incising of spruce to improve preservative penetration
1973 - IRG/WP 318
Large quantities of whitewood or Norway spruce (Picea abies) are regularly imported into the United Kingdom from continental Europe. In addition, increasing amounts of Sitka spruce (Picea sitchensis) are likely to become available over the next decade from the Forestry Commission. In many ways spruce is a good structural timber, eg it is relatively cheap and easily available, it has adequate strength properties and is easily worked. However, as a long life structural material it suffers the disadvantage of low resistance to fungal and insect attack of both its sapwood and heartwood. In addition, the material is resistant to impregnation with preservative fluid using normal pressure methods. If preservative penetration were improved, the species could be utilised in several building and fencing situations from which it is at present excluded because of its susceptibility to rapid biodegrade. Considerable effort has been spent in trying to improve the preservative impregnation of spruce wood and some degree of success has been achieved in the treatment of round timbers. Here the problem is to improve treatability of the sapwood band so that this is fully penetrated, providing a protective sleeve around untreated heartwood. Successful treatments of this type may be attained by water storage on 'ponding' prior to seasoning followed by pressure impregnation or by sap displacement treatment of freshly-felled logs (eg the Boucherie process). In 'square' sawn timber however, exposed surfaces contain a significant proportion of heartwood, which does not respond to either of the processes mentioned above. Penetration and absorption of impermeable species can be improved by incising. Generally, however, in the United Kingdom, incising has been employed only on large section engineering timbers (eg railway sleepers and marine piling) using a tooth size which damages the timber surface to an unacceptable extent see BS 913:1954 and 4072:1966) for application to the smaller section sizes encountered in building or light fencing material. The present work is concerned with the development of a level of incision sufficient to allow protection against biodegrade, without weakening the timber or damaging its surface to an unacceptable extent. The purpose of this account is to show the degree of improvement in penetration and absorption brought about by such incisions.
W B Banks


The degradation of wood surfaces by water
1984 - IRG/WP 3289
Thin radial/longitudinal sections (~100 µ) of Scots Pine (Pinus sylvestris) and lime (Tilia vulgaris), were exposed to deionised water over the temperature range 25-65°C. Losses in wet tensile strength and toughness occurred rapidly at temperatures from about 50°C upwards. After about 2 months' exposure pine lost some 10-30% of its tensile strength and 20-60% of its toughness. For lime the losses were somewhat greater, being about 20-60% for tensile strength and up to about 80% for toughness. Further prolonged exposure for about 18 months led to about 60% tensile strength loss in pine and 80% in lime. For both species some 90% loss in toughness occurred after this period of exposure. Dry tested specimens and those tested wet but at "zero span" retained a much higher proportion of their original strength. These specimens failed mainly by simple intra-fibre fracture, whereas the lime specimens tested wet at finite span, showed marked inter-fibre shear failure. No such clear cut distinction in failure mode could be observed with pine, although in this species also, scanning electron micrography showed marked degradation in the middle lamella region. It is believed that the phenomena reported are due purely to physicochemical processes and that they may contribute significantly to detachment of paints and other finishes from wood surfaces.
W B Banks, P D Evans


Alternative timbers to Iroko (Milicia excelsa) for various end-uses: Ghana’s offer
2004 - IRG/WP 04-10518
There are hundreds of timber species indigenous to Ghana and several exotic species have been extensively planted. The timber industry in Ghana is very important to the country’s economy. Despite its small size relative to the world trade in timber products, it has the potential to be a driving force in the development of the Ghanaian economy. The industry is currently going through a period of change and restructuring which is largely brought about by the need to address the issues of a reducing resource and to use the available resource more efficiently and to greater economic benefit by promoting the lesser used species as alternatives to the over-exploited primary species and also by developing the tertiary processing sector. Iroko (Milicia excelsa) is one of the primary species currently facing extinction and Dahoma (Piptadanistrum africanus), Ekki (Lophira elata), Kusia (Nauclea diderrichii) and Papao (Afzelia bella) are lesser-used species being promoted as good alternatives to Iroko for various end uses. Properties (mechanical, biological) and volumes of these species are compared to those of Iroko.
S A Amartey, Zeen Huang, A Attah


The biological effectiveness of wood modified with heptadecenylsuccinic anhydride against two brown rot fungi: Coniophora puteana and Gloeophyllum trabeum
1992 - IRG/WP 92-3705
A modified soil block test was carried out using wood samples reacted with heptadecenylsuccinic anhydride (ASA). This modification gave good resistance to decay brought about by the brown rot fungi Coniophora puteana and Gloeophyllum trabeum during the twelve week exposure period. Results indicated that there was a good correlation between increased loading of modifying reagent and an increase in effectiveness paralleled by a marked reduction in wood moisture content. The effective resistance threshold level was calculated to be about 30% weight gain of ASA. Further discussions regarding the mode of action are included.
C Codd, W B Banks, J A Cornfield, G R Williams


End grain sealing by polymer impregnation
1992 - IRG/WP 92-3708
The solution and dispersion characteristics of several hydrophobic derivatives of cellulose have been studied and the abilities of these polymers to afford effective end grain sealing of Corsican pine have been examined. Both solution and dispersion treatments with ethyl cellulose imparted good water repellency and end grain sealing to wood samples, however, the disperse systems possessed lower viscosities. Scanning Electron Microscopy (SEM) of treated samples and polymer radiolabelling/autoradiography studies indicated pit-membrane pore filtration of polymer particles close to the end grain. A range of esters (C2-C18 side chains) of Hydroxypropyl Cellulose have been prepared and characterised (FTIR, NMR). The acetyl, propyl and butyl esters formed coherent, flexible films. The C6, C9, C10 and C11 esters were essentially gums. However, the C18 (stearoyl) ester was found to form strong, wax like films, due to pronounced ester side-chain interactions. A number of the polymers were applied to Corsican pine test samples. Water repellent ability was found to strongly parallel the ability of the derivatives to form coherent polymer films. The C18 (stearoyl) ester exhibited impressive end grain sealing; outperforming all other systems tested at equivalent application levels. This work indicates that hydrophobic polymers that readily form strong films from solution or dispersion afford enhanced end grain sealing as compared to materials that simply produce a hydrophobic effect.
J M Lawther, W B Banks, D G Anderson, J A Cornfield


The degradation of wood surfaces by dilute acids
1985 - IRG/WP 3326
Thin radial/longitudinal sections(~100 µ) of Corsican Pine (Pinus nigra) and Lime (Tilia vulgaris), were exposed to Sulphuric, Sulphurous, nitric, acetic, and formic acid at 40°C in the pH range 2-6. After about 3 months exposure to Sulphuric, nitric, acetic and formic acid at pH 2.0 Pine lost some 20-25% of its tensile strength. Losses in tensile strength due to sulphurous acid were greater being about 60-70%. Further prolonged exposure to sulphurous acid for 12 months led to some 90% tensile strength loss in Pine and 95% in Lime. Tensile strength losses also occurred at pH 2.5 and 3.0. For Pine strength losses of some 40% and 20% occurred at pH 2.5 and 3.0 after 12 months exposure. For Lime the losses were somewhat greater being about 70% at pH 2.5 and 50% at pH 3.0. For both species even greater losses in toughness occurred after this period of exposure in the pH range 2-3. Signficant but more erratic losses in toughness also occurred at pH 3.5. The strength losses noted above are over and above those resulting due to exposure of the controls to deionized water alone. During a similar time period exposure to deionized water led to losses in tensile strength for both species of some 15-20%. Losses in toughness were even greater being in the range 20-40%. Lime specimens tested wet showed a tendency to fail by inter-fibre shear in the middle lamella region. Scanning electron micrography also showed degradation of the middle lamella in Pine. It is believed that the degradational phenomena reported here are due to physico-chemical processes and that they may contribute to the degradation of paints and other finishes from wood surfaces.
P D Evans, W B Banks


A substantively bonded water repellent treatment based on chromium carboxylates
1985 - IRG/WP 3344
Chromium carboxylates soluble in toluene have been synthesised and applied to Scots pine (Pinus sylvestris) sapwood. Without any further treatment, the compounds may be readily leached from wood surfaces with toluene. After a period of heating however, they become fixed to the cell wall, substantial amounts being resistant to leaching even under reflux conditions for several hours. Treatment of wood polysaccharide and lignin fractions separately, indicates that most of the fixation occurs to lignin, although the polysaccharides may be involved to a lesser extent. Swelling and water sorption tests have been carried out on small cross-sectional wafer specimens treated with the chromium carboxylates. These show that the treatments impart significant levels of water repellency and that the water repellent effect persists much better than with conventional resin/paraffin wax treatments.
J K Wright, W B Banks, W J Eilbeck


Borer fauna of Iran biodeterioration of wooden boats in Persian Gulf and Sea of Oman
1997 - IRG/WP 97-10230
In Persian Gulf and Sea of Oman (Indian Ocean) there are thousands of wooden boats from the time of Acheamenian and Sassand dynasti when India was a part of the Persian Empire. Now after 2500 years again, the Indian timbers specially Tectona Grandis and other Indian timbers and also tropical woods of Zanzibar (Tanzania) are brought to the Persian Gulf and Sea of Oman (Indian Ocean). Unfortunately the woods are not pressure impregnated but the boats are made from many kinds of woods (indigenous and exotic) and with bad oil impregnation (local impregnation). As a result the wooden boats are very badly attacked by different borers. None of the timber species currently in demand for boat building possesses any natural bioresistance, and will be completely destroyed within 6 to 12 months. The Iranian ministry of Jihad (reconstruction) should use pressure impregnation of wood with preservative chemicals, but the impregnation is inadequate. The need for long-term research in the field of marine biodeterioration for improving the efficiency of currently known control measures, with emphasis of application of non-polluting biological methods has been suggested in this paper.
P Niloufari


Changes in bacterial gut community of Reticulitermes flavipes (Kollar) and Reticulitermes tibialis banks after feeding on termiticidal bait material
2014 - IRG/WP 14-10819
In this study, 454-pyrosequencing was used to evaluate the effect of two termiticidal baits, hexaflumuron and diflubenzuron, on the bacterial gut community in two Reticulitermes flavipes colonies and one Reticulitermes tibialis colony. Results showed two bacterial groups to be most abundant in the gut, the Bacteroidetes and Spirochaetes, both of which do not appear to be adversely affected by bait treatment according to analysis conducted to date. Other major bacterial lineages present included Actinobacteria, Fibrobacteres, Firmicutes, Fusobacteria, Proteobacteria, Tenericutes, TM7, Verrucomicrobia and unclassified species, which matches closely with other studies examining termite gut bacteria. Phylogenetic analysis examining similarity among treated groups versus controls showed a treatment effect in both R. flavipes colonies, but no effect on R. tibialis samples. Overall community analysis also showed treatment groups were separated by their collection location indicating a distinct bacterial community within a colony. Future analysis will focus on the types of bacteria affected by bait treatment and the role of these changes in overall termite fitness.
R A Arango, F Green III, K F Raffa