Your search resulted in 75 documents. Displaying 25 entries per page.
Experiences from a Danish large scale test by means of a new method of treatment by attack of true dry rot fungus (Serpula lacrymans) in buildings
1994 - IRG/WP 94-10064
Experiences from a new and epoch-making method of treatment in connection with the repair of attack of the true dry rot fungus, Serpula lacrymans (Fr.) S.F. Gray, are described. The paper presents the background of a large scale test comprising repair of more than 150 Danish buildings over a period of approximate 5 years. The method being both gentle to the building and presenting savings of at least 70% compared with the traditionally known repairing methods is based on thorough recording of the extent of attack and examination of the vitality of the fungal attack combined with a changed chemical and constructive treatment including treatment by means of a newly developed heat treatment based on high frequency radio waves. Continuous controls have confirmed the applicability in practice of the method. Beyond the method, the paper discusses the consequences as regards security, possibilities of insurance and obtaining a mortgage loan.
O Munck, H Sundberg
Radio frequency heating times for sterilization radiata pine solid piles
2017 - IRG/WP 17-40815
In this work was sterilized wood packaging material of radiata pine, stacked as solid piles without stickers, for determining the heating times using radiofrequency treatment. The experiments were performed in a radio frequency semi-industrial equipment. The results showed that the radio frequency heating times increases with wood volume and that radio frequency treatments were faster than conventional vapour heat treatment.
H Esquivel, V Sepúlveda, J Torres, L Salvo, R A Ananías
Application of radio frequency heating to accelerate fixation of CCA in treated round-wood
1999 - IRG/WP 99-40133
The potential of radio frequency heating to accelerate the fixation of chromated copper arsenate (CCA) in treated round-wood was assessed. Pre-dried Douglas-fir and western red cedar round-wood sections were pressure treated with CCA in a pilot plant retort, after which they were placed individually in a pilot radio frequency (RF) chamber. Based upon the color reaction of chromotropic acid with hexavalent chromium and the quantitative assessment using diphenyl carbazide, fixation was achieved in less than 6 hours. During heating, the temperature at various locations inside the pole sections was monitored by fiber-optic thermocouples. The moisture profiles before, and after fixation, were also recorded. Further studies will examine other benefit of RF heating, including a) sterilization, and b) rapid drying of round-wood with minimum check formation.
Fang Fang, J N R Ruddick
TBTO absorption and penetration in pine joinery treated by various processes
1989 - IRG/WP 3523
Matched sections of several White pine (Pinus strobus) and Ponderosa pine (Pinus ponderosa) mouldings were treated with TBTO by Double vacuum, modified empty-cell, 15 second dip and several preheating treatments followed by a 15 s dip treatments. As expected the double vacuum and empty-cell (batch) treatments resulted in much greater retentions and penetrations than the dip treatments. The absorptions by the 15 s dip treatments could be improved significantly by preheating the wood to 60-90C° by microwave, radio-frequency or infra-red techniques. Since this approach is amenable to a continuous treatment process, it is being evaluated for potential commercial application.
P A Cooper, Y T Ung
Eradication of wood decay fungi by means of radio frequency
1998 - IRG/WP 98-10292
High frequency electromagnetic fields i.e. radio frequency (RF) are used in wood industry for heating, gluing and bending of wood and are also appropriate for eradicating of wood decay fungi and insects. We investigated the effects of RF exposure on wood samples which were in vitro infected by Coniophora puteana, Gloeophyllum trabeum and Lentinus lepideus. For each fungus, the lethal temperature and time of exposure were determined. The efficacy of RF treatment was visually evaluated from regeneration of mycelia by subsequent exposure of treated wood samples on growth media. The eradication was dependent on the fungus species, temperature and duration of exposure to RF of 4.75 MHz. The most sensitive was Coniophora puteana (destroyed in 4 minutes at 75°C), less sensitive Lentinus lepideus (in 10 minutes at 90°C) and the least, Gloeophyllum trabeum (in 12 minutes at 90°C). At low temperatures, the time of exposure had to be adequately longer.
F Pohleven, J Resnik, A Kobe
High-frequency monitoring of mass loss due to brown rot degradation of modified wood
2016 - IRG/WP 16-10862
Fungi growing in liquid culture undergoes three separate phases in which they i) adapt to the new environment, ii) grow unrestrictedly and exponentially, and iii) are inhibited to increase in number/mass due to lack of nutrients etc. Filamentous fungi have been shown to exhibit similar growth phases in a solid food substrate and have been modelled to grow in this way also in solid wood. In modified wood with high treatment levels, fungi cause no or little mass loss but the reason for this has not been fully explained. To be able to predict the service-life of modified wood, understanding the growth pattern of wood degrading fungi in these materials may be important. The aim of this study was to find out whether brown rot fungi undergoes the same growth phases in solid wood as in liquid culture and study the growth pattern of brown rot fungi in modified wood. This was done through high-frequent monitoring of mass loss over 300 days of exposure of acetylated and furfurylated wood to Postia placenta. Mass loss results of the untreated wood indicated clearly that the fungi in this material go through phases similar to phases seen in liquid cultures. However, the results for the modified wood materials were less clear. Little mass loss and a degradation rate 100 times lower than in the untreated wood during exponential growth may suggest that the fungi in the modified wood samples were still adapting to the new environment. On the other hand, the fact that mass was lost at all suggests that degradation did occur and that the fungi were growing exponentially.
R Ringman, A Pilgård, K Richter
Problems caused by termites in buildings in the State of Sao Paulo
1976 - IRG/WP 150
Termites are the main insects attacking buildings in the State of Sao Paulo - Brazil. Their attack occurs in wood and wooden materials as well as paper, textile, leather and so on.
M S Cavalcante
Improved equipment and technique for high pressure sap displacement impregnation of natural round wood
1972 - IRG/WP 309
Hitherto the main problem in the practical application of high pressure sap displacement impregnation (HPSD) has been in devising a satisfactory cap. Such a cap must be easily fitted to different size log ends to give a leak proof seal. The present contribution describes a new type of cap and sealing system designed to meet these requirements.
C G W Mason, F B Shorland
Changed susceptibility of the chemically and thermally degraded spruce wood to its attack by the dry rot fungus Serpula lacrymans
1999 - IRG/WP 99-10322
In buildings, some intentional or unintended situations can occur at which some wood products are exposed to aggressive chemicals and also to higher temperatures. Occasional activity of fungi on such pre-attacked wood products can be either higher or lower. This paper deals with changes in the susceptibility of spruce wood (Picea abies L. Karst.) to attack by the dry rot fungus Serpula lacrymans, in such situations, when the wood samples 8.5x8.5x120 mm3 (RxTxL) were first pre-treated with 1% water solutions of selected acids (H2SO4, CH3COOH), bases (NaOH, NH4OH) or oxidizing agent (H2O2), or they were also exposed to a higher temperature (190°C/3h). The activity of S. lacrymans was totally restricted only in one situation, if the wood was pre-treated with sulphuric acid and then exposed to 190°C. On the other hand, specimens pre-treated with ammonium hydroxide were more susceptible to bio-attack (in both situations: without or with high temperature pre-treatment effect) than sound ones.
An investigation concerning Camponotus spp. distribution and damage in buildings in Sweden
1985 - IRG/WP 1248
This is a report of an investigation by a Swedish insurance company on the occurrences of damage by Carpenter ants during 1974 to 1981. The distribution of damage in walls, roofs and floors of both permanent homes and summer-houses has been assessed. It is concluded that the increased frequency of attack is becoming economically serious.
V Butovitsch, K-J Hedqvist, C Tornberg
Wood decay in Danish buildings
1985 - IRG/WP 1261
At Technological Institute identification of fungi and advisory activity concerning repair of damages has taken place since 1935. Statistical analyses based on material from 1982 and 1983 are compared to earlier investigations worked out by L. Harmsen. The material shows that building traditions influence the diversity and frequency of fungal species. Many fungal damages in the last decade have showed that it is very important to use timber in a suitable manner not forgetting old building traditions. The conditions of fungal attack must be analysed and followed up by improvement of constructive and chemical wood protection.
A P Koch
New developments in wood preservation
1974 - IRG/WP 335
Most of the developments in wood preservation in recent years have been stimulated by changing circumstances, particularly the increasing interest in reducing hazards and environmental, pollution but also the serious difficulties that are now being encountered in obtaining economic supplies of established preservatives. There is perhaps a danger that new controls to reduce pollution dangers may be too severe.
B A Richardson
Preservative treatment of Pinus elliottii
1987 - IRG/WP 3435
The treatment of Pinus elliottii with copper-chrome-arsenic preservative by four alternative seasoning and treatment methods is investigated. Steam conditioning followed by either alternating pressure method (APM) or 'Q' treatment resulted in inadequate preservative penetration. Air drying or high temperature drying followed by the Bethell process resulted in a high standard of treatment.
P Vinden, L Carter
Decay resistance of high performance biocomposites based on chemically modified fibres
1998 - IRG/WP 98-40120
Different partners within the framework of a European research project produced high performance biocomposites aiming at the utilisation of board materials as durable products both in dimensional and biological degrading circumstances. This paper summarises test data, which indicate the potential of board materials produced with modified fibre material. The chemical modifications applied cover a range of technologies, which were selected for scaling up experiments. Acetylation, as well as alternative methods like maleiation, phthalylation, succinylation, oxidation and silylation were investigated. Fibre source, density variation and the use of several types of glues were parameters of the total set-up. Basidiomycete testing was carried out using specific methodology for board materials elaborated in CEN standardisation committees.
V Rijckaert, J Van Acker, M Stevens
Exterior wood stains
1980 - IRG/WP 3135
Experience has shown that conventional paints cannot now be relied upon to provide a complete seal against water entry, that in practice water can often circumvent the film and that the paint, far from serving to keep water out will seal it in. Moreover present-day paints are often subject to localised and premature failure out of doors and consequently entail high maintenance costs. Problems of wood decay and premature paint failure reached a high level during the 1960s, and led to the acceptance of the need for the preservative treatment of softwood joinery and cladding. The question remains however, whether, in the light of changes in the quality of timber and how it is used, the traditional approach of attempting to seal the outer surface of the wood is still valid, or should be abandoned in favour of using different types of finish which are more permeable to moisture and prevent it accumulating in the timber. One of the reasons for the remarkable success of semi-transparent exterior wood stains is that they met the demand for finishes of increased water vapour permeability for timber which was susceptible to decay. They also possessed two other important attractions: they provided natural finishes for exterior timber which were without the technical problems of clear varnish; and their mode of breakdown by erosion reduced the preparation work in maintenance and hence the overall maintenance costs. These are valid commendations for stains and remain important factors encouraging their use. Stains offer the architect additional design freedom and, used effectively, can make a pleasing contribution to the appearance of modern buildings. They do reduce average moisture levels in the timber and are simple to maintain, though these advantages may be offset to some extent if more frequent maintenance is necessary and if the higher permeability creates problems from dimensional movement.
E R Miller
Resin bleed after light organic solvent preservative treatment - the effect of drying method and process type
1986 - IRG/WP 3378
The effects of drying method and treatment process type on resin bleed were investigated. High-temperature drying of resinous radiata pine (Pinus radiata D. Don) heartwood resulted in improved wood permeability, higher preservative uptake, and greater resin bleed when treated by the Rueping process. Resin bleed was reduced substantially when timber was treated by the Lowry process, and totally eliminated when Bethell-treated. The incorporation of 2% wax into the preservative formulation may control resin bleed after Rueping treatment.
Observations on the uptake and penetration of various liquids in clear heartwood and sapwood of Pinus radiata D.Don
1983 - IRG/WP 3224
Volumetric uptake of water (aqueous copper-chrome-arsenic (CCA)) or methanol, applied by bulk hydrostatic pressure to air dried clear heartwood specimens of Pinus radiata D. Don, far exceeds that of a wide variety of polar and non-polar solvents. In air dried sapwood, the volumetric uptake of CCA tends to be less than that achieved for most solvents including methanol. No comprehensive explanation of the penetration mechanism in these two substrates can yet be offered. High temperature drying effects a significant increase of volumetric uptake of all liquids by heartwood, but not by sapwood, possibly because air dried material is nearly saturated after pressure treatment.
J E Barnacle
The effect of high temperature and long pressing time on the dimensional stability and decay resistance of OSB
2002 - IRG/WP 02-40237
The exterior use of OSB is restricted because when it is exposed to wet conditions swelling, loss of internal bond strength (IB) and decay occur. In this study an alternative process of pressing which results in the production of dimensionally stable and a more decay resistant strandboard was investigated. Boards were pressed at elevated temperatures for prolonged pressing cycles and their physical (thickness swelling and water absorption after 2 and 24 hours soak), mechanical properties (IB, MOR, MOE) and decay resistance were assessed. Analysis of variance (ANOVA, p=0.005) between pressing time/temperature and each property tested were used for the assessment of the results. The decay resistance of the boards was tested according to a draft European standard (DD ENV 12038: 1996) with a slight modification to the sample size. Boards were tested against Coniophora puteana, Postia placenta, Trametes versicolor and Pleurotus ostreatus. The results of this study showed that the increase of pressing time and temperature resulted in significant reductions in the thickness swelling and water absorption of the boards. The treatment had little effect on board mechanical properties. The resistance to fungal biodegradation was significantly improved at the higher temperature / pressing time combinations tested. The results of this study show that the production of a dimensionally stable and a more decay resistant OSB is possible without excessive use of preservative chemicals. If adopted these findings may lead to the development of new wood-based panel products (non-preserved dimensional stable and decay resistant hazard class 3-OSB) which may replace preservative treated plywood and solid wood for many exterior construction applications.
G J Goroyias, M D C Hale
High CCA retentions and the protection of eucalypt power poles
1983 - IRG/WP 3226
Tasmanian power pole material treated to high retentions, was analysed to accurately determine the amount of CCA preservative in the timber. Material from the same disc was subsequently exposed in unsterile soil in order to determine the effectiveness of treatment. Results showed that even at high retention levels, soft-rot attack was not prevented. Fourteen further poles were sampled, but this time gradient sampling was carried out in order to determine the penetration pattern of the CCA salts. These poles were treated to retention levels in the order of 40 kg/m³. Again material from these poles was used for exposure testing. Significant weight loss was found after sixteen weeks exposure. The results indicate that high loadings of CCA present in the sapwood of these eucalypts, have not prevented the onset and progression of soft-rot decay.
L E Leightley, J Norton
Durability of surface preserved wood particle boards submitted to atmospherical influence
1995 - IRG/WP 95-40039
The worldwide problem of the continuously growing deficit of high quality natural wood material has caused the attempts of many research workers to find effective composites such as wood particle boards (WPBs) for replacing the massive wood for constructive purposes, depending on where the boards are exploited - in the open or under a shed, they are submitted to various climatic factors such as heating, drying, moistening, frosting, irradiation, that's why for reaching high atmospheric resistance, it is very important, a durable protection of the WPBs with suitable coatings against the atmospheric influence to be ensured.
Occurrence, prevention and repair of Dry Rot
1990 - IRG/WP 1439
Information about the frequency, detection, identification and repair of Dry Rot attacks (Serpula lacrymans) is summarized from 13 European countries. Based on 28 completed and returned questionnaires it appears that Dry Rot attacks are recognized in all countries participating, and that there is an appreciable similarity in the frequency of attacks and methods of detection and identification. However, the method of repair is often rather different between the countries and sometimes even within the same country. These differences are reflected in the methods of repair as well as in the chemical treatment to prevent further spread of the attack. Research concerning alternative methods of Dry Rot treatments is only performed in a few countries.
A P Koch
Quality of timber impregnated with preservatives of class AB
after three years in service
2002 - IRG/WP 02-20241
Quality of impregnated timber is most often expressed by penetration and retention of the preservative used. Relatively less information is available about the performance of the final product, e.g. decks, panels etc. regarding product’s surface checks, deformations and overall appearance. Together with the timber durability, the above mention features are of esthetical importance in the above ground performance of timber. A comprehensive Nordic project dealing with pre-treatment, impregnation, durability and performance of Scots pine timber impregnated with copper-based preservatives for above ground use (class AB) was recently finished. The results from an above ground trail concerning the quality of timber are presented. The timber was dried in a conventional progressive, batch and high temperature kiln prior to impregnation. A significantly better quality regarding checks, deformations and deviation of the final moisture content, was achieved after conventional batch and high temperature dryings. Three preservatives (Kemwood ACQ 1900, Tanalith E and Wolmanit CX-8) were impregnated. The high temperature drying ensured the best penetration of all preservatives, but the retention was lower compared to conventional progressive and batch kiln dried timber. A part of the planks were conventionally kiln dried after the impregnation, the second part was air dried. Two decks with planks covering the variations in primary drying and preservative used were exposed; the former deck was in the open, the later one was under a shelter. After three years in service the planks were assessed regarding checks, deformations and moisture content. All three preservatives showed satisfactory appearance and no indication of decay was found. The deformations were comparable to those measured directly after final drying; the type of exposure had effect on the checks and moisture content of timber.
Soil bed studies of the dimensional stability of composite products
1999 - IRG/WP 99-40134
The influence of boron and isocyanate resin on the dimensional stability of high moisture resistant particleboard was assessed after burial in a soil bed for one month. The samples were treated with two levels of a boron compound and coated in isocyanate resin. The samples were randomly placed in a fungal cellar in soils of two different water holding capacities. Weight differences and dimensional changes were measured after one month. The results suggest that there is a significant increase in weight and thickness swelling. Boron treatment prior to resin impregnation also appears to have assisted moisture absorption.
K M Filcock, P Vinden
Effects of drying processes on termite feeding behaviour against Japanese larch wood
2001 - IRG/WP 01-10390
We investigated the effects of current drying schedules for larch lumbers on the termite feedings. Thermal analyses were also conducted to investigate degradation of wood components. Choice feeding tests showed specimens dried under high-temperature schedules were evidently susceptible against termite attacks. These schedules produced the feeding-attractants, which were suggested by the TGA results compared to the control samples. The results of this study indicated that the acceleration of termite feeding is taken place even under comparatively lower temperature than that of our previous researches.
S Doi, Y Kurimoto, H Takiuchi, M Aoyama
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