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Utilization of plasma treatments in the field of wood protection
2021 - IRG/WP 21-40912
Plasma treatments have been used for modification of surfaces of wood and wood-based materials for some decades and solutions were developed to apply it for wood protection. This contribution aims to present the background, introduce the available plasma technology, and to give an overview on the typical applications and benefits.
S Dahle, H Militz

Annual Report 2020
2021 - IRG/WP 21-60486
IRG Secretariat

Revised budget for 2021 (forecast Oct 2021)
2021 - IRG/WP 21-60487
IRG Secretariat

Buget for 2022
2021 - IRG/WP 21-60488
IRG Secretariat

IRG52 Webinar Programme
2021 - IRG/WP 21-60484
IRG Secretariat

Plenary 2021 Agenda
2021 - IRG/WP 21-60485
IRG Secretariat

Performance of resin-treated solid wood and laminated veneer lumber (LVL) under marine conditions
2021 - IRG/WP 21-10973
Wood is a traditional building material in the marine environment, where it is exposed to extremely harsh conditions. Most of the indigenous softwood and hardwood species in Europe are not durable against attack by marine organisms. Recently, wood modification has been considered as an alternative to protect non-durable wood species under use class (UC) 5 (EN 335, 2013) conditions. The present study focused on treatment of solid wood and laminated veneer lumber (LVL) with the thermosetting resin 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU), its derivatives and low molecular phenol-formaldehyde (PF). The results evidenced that treatments with formaldehyde-containing thermosetting resins like DMDHEU and PF improved the resistance against attack by shipworms significantly. The latter was shown for both, solid wood and LVL specimens. In Scots pine sapwood specimens, treatment with DMDHEU caused higher improvements in the resistance against shipworm attack compared to Radiata pine and poplar specimens. Formaldehyde-free DMDHEU derivatives did not provide any resistance against marine borers compared to untreated control panels. In summary, wood modification with thermosetting resins has good potential to be used in the marine environment (UC 5). However, the mechanisms of protective action are not fully understood yet and require further studies on how curing processes, chemical distribution and production processes for wood-based composites affect the marine borer resistance. Besides that, an upscaling to large-sized dimensions is essential to implement such innovative technologies as building materials under UC 5 conditions in the near future.
L Emmerich, C Brischke, S Bicke, H Militz

Assessing the risk of marine borer attack of the timber trestles and decay of timber above the intertidal zone of the Barmouth Viaduct
2021 - IRG/WP 21-10974
The Barmouth Viaduct is a Grade II* listed structure which carries the single track of the Dovey Junction to Pwllheli line and footway over the Mawddach estuary. It is in a marine environment where timber below the high tide mark is at most risk in Use Class 5 and all timber above in Use Class 3.2, permanently exposed to the risk of wetting. The structure consists of a timber trestle viaduct of 113 timber spans with 5 steel spans over the deep-water channel. It is of historic importance and is the longest functioning timber viaduct in the UK and is a vital link on the Cambrian line. However, the structure is ageing and under attack from a number of biological agents. Within the intertidal zone, the structure is at risk of attack by shipworm. Above the intertidal zone, the structure is permanently at risk of attack by wood decaying fungi. The structure is undergoing a £20 million refit with much of the work focussing on the renewal of timber that has been attacked by biological agents. The combination of an ageing infrastructure and stressed maintenance budgets provides the impetus to develop innovative methods to support the asset management plan of the structure. Understanding the performance of materials and their rates of deterioration may inform design choices. Moreover, understanding the impact of climate change and local environmental factors and how this can change the distribution of marine borers and affect the risk of decay can also support the long-term asset management of the viaduct.
J R Williams

Validating a short-term laboratory method to assess the resistance of timber to biodegradation by marine wood-borers
2021 - IRG/WP 21-10975
Novel approaches to protecting wood in coastal and marine environments are needed as the use of traditional broad-spectrum biocides are now restricted. Wood is widely utilised in marine environments where it can be rapidly degraded by wood-boring organisms, causing billions of dollars of damage per annum. Biocidal compounds such as CCA and creosote have been popular treatments for timber products during the last century but have since been restricted or banned in several countries, including the UK. Novel methods in wood modification and protection are therefore required to replace such techniques. Use of lesser-utilised timber species and wood modification offers a promising alternative approach of reducing damage by marine wood-borers. Processes of modification are evolving rapidly, so long-term testing needs to be supplemented by rapid testing methods in order to speed up process development. New potential products must undergo thorough testing in order to be commercially viable and to minimise environmental impacts. Marine trials require long exposure periods and are thus expensive and slow to yield meaningful results. Laboratory tests, however, provide a much quicker alternative to test novel timber products against gribble attack. A standard method for assessing the feeding rate of the wood-boring crustacean the gribble (Limnoria spp.) can be used to determine if the wood affects feeding rate and mortality. This is investigated through assessing faecal pellet production (used as an indicator of feeding rate), vitality, and mortality rates. These data combined, can begin to identify products that have the potential to be resistant marine wood-borer attack.
L S Martin, J R Shipway, G P Malyon, S M Cragg

Experience Experience from over 20 years of field trials of resin treated wood – Marine borer resistance of MMF and DMDHEU modified wood
2021 - IRG/WP 21-10976
In 1999 a field test of Scots pine treated with MMF (Methylated Melamine Formaldehyde) resin and acetylated Scots pine post treated with MMF resin was started. Six years later a commissioned full NWPC test for BASF of Belmadur® (DMDHEU resin treated wood) was started at the same site. The testing, according to European Standard EN 275, was done in a bay by Kristineberg Marine Research Station on the Swedish west coast. The marine borer (mainly Teredo navalis) activity at the test site is very high, always resulting in failure of control specimens within a year. The two sets of CCA-treated reference specimen at low retention level (approximately UC3 level) failed with an average service life of 3.6 and 3.8 years, respectively. The first set of CCA-treated reference specimens at the high retention level (UC5 level) failed with an average service life of 13.5 years. The two sets of MMF resin modified wood specimens at low and medium treatment level (WPG=11 and 23, respectively) have failed with 4.8 and 15.3 years’ service life, respectively. The set with high MMF treatment level (WPG=47) is only slightly attacked after 21 years. Acetylated wood post treated with MMF resin at low retention level (WPG=19+8) are severely attacked but performing better than CCA at high retention level. Acetylated wood specimens post treated with MMF resin at medium retention level (WPG=21+19) are rated sound after 21 years. All DMDHEU specimens at all treatment levels (WPG = 28, 35 and 42, respectively) are perfectly sound after 15 years of exposure. DMDHEU seems to provide excellent resistance to borer attack at the treatment levels included in this test.
M Westin, P Larsson Brelid, A O Rapp, J Habicht

Plasma treatment of wood - a review of 15 years of research in Göttingen
2021 - IRG/WP 21-40913
Wood is an important renewable resource and can be found omnipresent in everyday life. Its natural properties offer numerous advantages regarding physical, mechanical but also aesthetic aspects, but also challenges that one has to address with various modification methods. Driven by the desire to promote the use of promising new technologies using plasmas, there has been a close research network between the University of Göttingen and the University of Applied Sciences and Arts (HAWK) Göttingen for more than 15 years. The interdisciplinary research environment bringing together scientists and engineers thus created a beneficial perspective of various core competencies of the partners involved. The application of atmospheric pressure plasma using air as working gas results in a hydrophilization of the material surface. Resulting from these changes, numerous improvements in the area of adhesion properties of wood and wood-based materials have already been achieved. Improvements of adhesion properties of paint and adhesives could also be shown for both solid wood and wood-plastic composites. This offers a great potential for downstream production steps, such as coatings or bonding in the wood industry. Additionally, improved impregnation behaviour represents a significant improvement, particularly in the area of veneer materials, and offers new opportunities for wet-chemical wood modification. Protective layers have also been applied on wood and wood based products by various plasma techniques. Biocidal effects have already been achieved with plasma-based application of nanoscale metal particles and functional layers based on e.g. copper. UV-protecting, emission-reducing and self-cleaning layers have been researched as well as solvent free plasma spraying.
P Sauerbier, R Köhler, G Avramidis, W Viöl, H Militz

Influence of weathering on surface roughness of thermally modified wood
2021 - IRG/WP 21-40915
Thermally modified wood is exposed to weathering similarly as other wood-based building materials. It has been reported that if thermally modified wood is exposed to weathering, its moisture performance might decrease fairly fast. The aim of this study was to determine whether this phenomenon is associated with crack formations or roughness. Norway spruce, thermally modified spruce, wax-treated thermally modified spruce, and European larch heartwood samples were exposed to artificial accelerated weathering and natural weathering for 9, 18, and 27 months. Samples were subsequently isolated and their roughness was determined with a confocal laser scanning microscope on axial and longitudinal surfaces at 10× and 50× magnification. After weathering, roughness increased on both axial and longitudinal surfaces. This was evident from the profile 2D measurements (Ra) and surface 3D measurements (Sa). The effect of natural weathering on roughness was higher than artificial accelerated weathering, presumably due to synergistic effects of abiotic and biotic factors.
E Kerzic, B Lesar, M Humar

Surface morphology and short-term water uptake of charred and coated wood
2021 - IRG/WP 21-40916
Charring of the wood surface represents a traditional alternative surface treatment technique with the purpose of aesthetics and protection. By the treatment with flame the surface of wood becomes carbonized and a few millimetres thick charred layer is formed on the top of the wooden element. Further, the charred layer can be removed by brushing, which accentuates the structure of the surface. Additionally, for appearance and protective purposes, a different kind of oils and coatings may be applied to the charred wood surfaces. Although this type of wood surface protection has been known for centuries, there is still a lack of knowledge about the water uptake properties of charred and surface finished wood. The aim of the present study was to find out how the treatment with charring, charring and brushing, and surface finishing affect the surface morphology of Norway spruce (S) and European larch (L) wood. By immersing the samples with treated radial surfaces in deionized water, the water uptake in the samples was monitored via the mass increase measurements on the tensiometer. Confocal laser scanning microscope examination showed that charring of wood greatly increased the surface roughness (S by 10-times and L by 6.5-times). Brushing of the charred wood surface further increased surface roughness (S by 21-times and L by for 23-times), completely removing the earlywood structure, while the latewood regions remained present. Surface finishing with water-borne stain noticeably increased only the roughness of the sanded wood surfaces, while the roughness of the other surfaces was not affected. In general, the S wood absorbed more water than the L wood. The highest amount of water was absorbed by the samples with the charred surface (S 0.048 g·cm–2, L 0.031 g·cm–2) and even the surface finishing of these could not prevent water absorption. The water uptake of the other surface types was quite comparable (S about 0.026 g·cm–2, L 0.021 g·cm–2). The higher water uptake seemed to be related to the higher surface roughness or to the specific surface to which the water molecules can attach and possibly penetrate into the wood.
J Zigon

Effect of MVOC exposure on mycelial growth of wood rotting fungi
2021 - IRG/WP 21-10977
It is well known that wood rotting fungi produce microbial volatile organic compounds (MVOCs) as metabolites. In our previous studies, we have found that some MVOCs produced by wood rotting fungi are common to fungal species tested in the studies, while others are specific to each species. Furthermore, it has been also shown that each wood rotting fungi do not always produce the same type of MVOCs in the same quantity, but that the production patterns of MVOCs change depending on the decay stage and nutrient source. These facts suggest that MVOCs produced by wood rotting fungi may be associated with physiological activities, but information on this is limited. To obtain the knowledge of the effects of MVOC exposure on physiological activities of wood rotting fungi, in the present study, 14 MVOCs (1-octen-3-ol, 1-octen, 2,5-dimethylfuran, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-2-butanone, 3-octanol, 3-octanone, methyl 2-furoate, methyl benzoate, methyl tiglate, nonane, octane and thujopsene) were diluted to 1% with acetone, and then exposed each at different concentration to four species of wood rotting fungi (white-rot fungi Trametes versicolor, and brown-rot fungi Coniophora puteana, Fomitopsis palustris and Gloeophyllum trabeum). After a certain period incubation, mycelial growth was measured based on the diameter of the colony where the mycelium has spread. Consequently, it was suggested that the effect of MVOCs exposure on mycelial growth varied depending on the environment in which the fungus was growing.
S Horikawa, R Konuma, M Yoshida

Decomposition and metabolism of gaseous COS by wood rotting fungi
2021 - IRG/WP 21-10978
Previous studies on physiology of wood rotting fungi have mostly focused on the metabolisms of carbon and nitrogen sources. On the other hand, despite of the biological importance of minerals such as sulfur, our knowledge of their metabolic systems is limited. The sulfur source for wood-rotting fungi has been thought to be water-soluble sulfur compounds such as sulfate esters and cysteine, which are present in very small amounts in wood. Recently, our research group has shown that filamentous ascomycetous fungus isolated from soil have the ability to degrade carbonyl sulfide (COS), which is a gaseous sulfur compound, and it can use COS as a sulfur source. Based on the background, in the present study, we hypothesized that the wood rotting fungi also uses a gaseous COS in the air, to grow in wood. In order to prove this hypothesis, we measured the COS-degrading activity of nine wood rotting fungi (brown-rot fungi Gloeophyllum trabeum, Coniophora puteana, Fomitopsis palustris, Fomitopsis pinicola, Neolentinus suffrutescens, Wolphiporia cocos and Serpula lacrymans, and white-rot fungi Trametes versicolor and, Pleurotus ostreatus) and found that all of them had COS-degrading activity. Among the above fungi, G. trabeum, a model brown-rot fungus, was used to investigate the effect of COS addition on the growth of the fungus. In addition, to clarify the effect of COS addition on metabolites, metabolome analysis focusing on sulfur-containing compounds was conducted, and several sulfur-containing metabolites and compounds involved in sulfur metabolism were detected. These results suggest the existence of a novel sulfur acquisition pathway using gaseous COS by wood rotting fungi
R Iizuka, O Iwao, Y Katayama, M Yoshida

The iron reduction by chemical components of wood blocks decayed by wood rotting fungi
2021 - IRG/WP 21-10979
Brown-rot fungi, a group of wood rotting fungi, is well known to be one of major microorganisms that cause the deterioration of wooden buildings in Japan and have been considered to use chelator-mediated Fenton (CMF) reaction in concert with hydrolytic and redox enzymes for degradation of wood cell wall. CMF can be described as a non-enzymatic degradation system that utilizes hydroxyl radicals produced by the reaction of hydrogen peroxide with ferrous iron in the presence of chelator, and therefore, the reduction process of ferric iron present in wood cell walls is one of the key reactions in this process. To date, various candidates such as low-molecular weight aromatic metabolites produced by fungi, proteins, and lignolytic products have been proposed as iron-reducing compounds. In addition, lignin polymer has been also reported to have the ability of iron reduction although detailed mechanism is not still unknown. In the present study, the authors investigated the iron reduction with wood flour, which was expected to contain both a part of soluble compounds and cell wall polymers, using ferrozine assay in order to obtain the knowledge of iron reduction mechanism. We show that iron reduction capacity by decayed wood samples was higher than that by the samples of sound wood.
R R Kondo, Y Horikawa, K Ando, B Goodell, M Yoshida

Occurrence of synanthropic beetles (Coleoptera Ptinidae) and checkered beetles (Coleoptera Cleridae) in relation to climatic factors in historical buildings from North-Eastern Germany
2021 - IRG/WP 21-10980
Predatory checkered beetles occur in many historical buildings. Thus, it is essential to learn more about the ecology of these beetles, specifically for their further use as suitable beneficial organisms in biological control of wood-destroying insects. In this study, indoor climatic conditions were examined as a major factor influencing their occurrence and that of their prey Anobium punctatum and Xestobium rufovillosum. For this purpose, monitoring and climate measurements were implemented in nine historic buildings in North-Eastern Germany (Mecklenburg-Vorpommern). A collective occurrence of Opilo domesticus and Korynetes caeruleus together with the wood boring pests was shown via sticky traps and collections of adult beetles. The exit holes of O. domesticus and Opilo mollis in paper covers used to monitor hatching-activity are not sufficiently species-specific and are therefore not considered in the evaluation of the climate data. Usually only annual and monthly mean values for temperature and relative humidity have been considered to discuss the occurrence of the insects mentioned. Anobium punctatum and X. rufovillosum, as well as their predators K. caeruleus and O. domesticus, have been found in half-timbered and solid structures. According to this, their climatic requirements must be quite similar. As a new study approach, climatic conditions for the period of walking and flight activity (reproductive phase via sticky traps and collections) were studied separately for both, the beneficial insects and wood pests. The results obtained so far partially showed significant differences for the insect species investigated. Anobium punctatum reproduces within narrowly defined temperature intervals with an optimum between 15.5 - 18 °C. For the reproductive phase of O. domesticus, the optimal temperatures are between 16.5 - 18 °C, up to about 23 °C, which almost exactly corresponds to those of A. punctatum. However, there are differences in humidity requirements. The beetles of O. domesticus have only been recorded at a rel. humidity of 64 - 73 %. This range of rel. humidity is narrower than for A. punctatum, whose beetles are found in buildings with rel. humidity from 55 - 80 %. These differences in climatic requirements may be part of the reason for the less frequent occurrence of O. domesticus beetles in only three buildings and the greater distribution and abundance of A. punctatum in all nine buildings. The obtained results from these studies and those of previous findings regarding climatic conditions will help successful breeding of checkered beetles in the laboratory for biological control purposes.
C Baar, C von Laar, M Willert, H Bombeck

Comparison of AE-apparatus for detection of activity of Old house borer larvae, including reality check
2021 - IRG/WP 21-10981
As part of the German funded project ‘InsectDetect’ comparative measurements were done with three different Acoustic-Emission-(AE)-apparatus on 14 pine beams in order to assess presence of active attack by the Old house borer (Hylotrupes bajulus (L.)). In all beams active attack was measured, though in varying intensity. This was corroborated by completely dissecting 10 of the beams. All three AE-systems proved suitable to find active attack, although their results in terms of numbers of events are different even when used in the same situation. Therefore, it is important that the operator is familiar with the technical functioning of the system that is used in order to be able to interpret the results reliably. The dissection of the beams showed that there is also an element of chance in these measurements regarding proximity of sensors to gnawing larvae and temporal larval inactivity. Still, such measurements with these apparatuses can give an answer to the question whether active attack of wood-boring insects is present.
J Creemers, B Plinke, U Noldt

Genetic relationships of local infestations by Anobium punctatum, Xestobium rufovillosum and their associated predator Korynetes caeruleus from buildings in North-Eastern Germany
2021 - IRG/WP 21-10982
Wood-destroying pests such as Anobium punctatum and Xestobium rufovillosum cause damage to art and cultural objects as well as to buildings. Monitoring population dynamics of pest species as well as of their naturally occurring counterparts are an essential part in the development of biological control measures as alternatives to conventional wood protection. Therefore, both the dispersal and homogeneity of pest and beneficial insect populations across multiple sites and buildings were investigated in the present study using DNA barcoding. Specifically, beetles of Anobium punctatum (de Geer 1774) (Coleoptera, Ptinidae), Xestobium rufovillosum (de Geer, 1974) (Coloeptera, Ptinidae), and Korynetes caeruleus (de Geer 1775) (Coleoptera, Cleridae) were collected from buildings at four different sites in Mecklenburg-Western Pomerania, North-Eastern Germany. DNA analysis was performed using mitochondrial cytochrome c oxidase subunit I (COI). For A. punctatum, low base pair variability was found in the gene segment studied (4-5 SNPs) within one building (Greven) and between four spatially separated sites. Conversely, in X. rufovillosum, the sequences from two sites studied were homogeneous within a site but differed between locations by nine base pair positions (SNPs). The main result of this study is that the pests A. punctatum and X. rufovillosum showed a higher variability in the investigated gene segment than the natural counterpart K. caeruleus.
C von Laar, C Baar, R Plarre, D P McMahon

Marine borer resistance of various wood materials in Japan
2021 - IRG/WP 21-10983
Wood resistance against marine borer was intensively studied in the 1940s in Japan, but the research activities on the subject diminished afterward, as the use of wooden marine structures and ships decreased. Today, however, use of wood as a construction material is officially promoted for its environmental benefits. The author started to immerse some wood materials in the seawater pool at PARI (Port and Airport Research Institute) and has continued to study marine borer resistance of various wood materials in the last two decades. In this paper some of the results of those studies are described. Untreated wood samples of various species were immersed in the seawater and the shipworm (Teredo navalis) and gribble (Limnoria sp.) feeding damage was evaluated by the dry mass reduction rates and the observation of the cross sections of the samples. Although some species of wood showed relatively high resistance against the marine borers, no undamaged wood species has been found so far. Wood samples modified by impregnation of low molecular phenolic resin were immersed, and they remained after 15 years of immersion, while some parts of them were severely attacked by gribbles. Thermally treated samples have been in the seawater for 13 years, and only the samples processed at 237.5°C for 5 hours remained without damage by marine borers. The effects of wrapping of wood against marine borers were also studied. The wood samples wrapped with polyethylene mesh with nominal opening sizes of 0.224mm or less were not attacked by shipworms as of 16 months of immersion. The bending rigidities of the wood samples glued carbon fiber sheets with epoxy resin maintained 50% or more of the initial values after 15 years of immersion.
M Yamada

Studies on the material resistance and moisture dynamics of Douglas fir and Sitka spruce from Slovenia
2021 - IRG/WP 21-20677
Wood in outdoor applications is subject to various decomposition factors. Wood degradation can be prevented by construction details, biocide protection of wood, wood modification, or selection of naturally durable wood species. Unfortunately, the majority of timber species in Europe do not have naturally durable wood. Imported tree species represent a new pool from which we can draw wood species with better natural durability. Wood performance in the outdoor application is a function of biologically active compounds (extractives) and water exclusion efficacy. Based on these parameters, we can estimate the resistance dose that reflects the material property of wood. Recently, the model most commonly used for this purpose is Meyer-Veltrup. Literature data indicate that the durability of the wood from native and new sites is not always comparable, so it is necessary to determine the resistance of non-native wood species from new sites. This paper presents original data on the overall wood durability of American Douglas fir (Pseudotsuga menziesii) and Sitka (Picea sitchensis). Experimental data show that the adult heartwood of Douglas fir is more durable than the wood of European larch (Larix decidua), and Sitka spruce is more durable than the wood of Norway spruce (Picea abies). Among the wood species considered, the wood of the American Douglas fir shows the greatest potential for outdoor use.
M Humar, B Lesar, D Krzisnik, E Kerzic, R Brus

Development of software to automate the quantification of the extent of penetration of treated wood
2021 - IRG/WP 21-20678
In Japan, Japanese Agricultural Standard (JAS) by the Ministry of Agriculture, Forestry and Fisheries and Approved Quality (AQ) by the Japan Housing and Wood Technology Center have established the penetration standard for treated wood. In our company, we measure the degree of penetration by either visual assessment or image processing. In the visual assessment, the degree of penetration is determined by calculation in our head. Although this method allows for quick measurement, it requires experience for accurate measurement. On the other hand, in the case of image processing, the degree of penetration is determined by measuring the area of coloration using some software e.g., Microsoft Paint, ImageJ. Although image processing is more time-consuming than visual assessment, it does not require the same experience as visual assessment. Since these two methods are not both quick and easy, we thought there was room for improvement. Therefore, the purpose of this study was to establish a quick and easy method for measuring the degree of penetration. To achieve this goal, we developed a new software program for measuring the degree of penetration. The program is written in Python and uses RGB color images. The procedure of the program is to identify the contour of the wood cross-section and classify each pixel as penetrated or unpenetrated. The number of pixels classified as penetrated is then divided by that of total pixels to calculate the degree of penetration, which is output to a spreadsheet automatically. As a result of using the software, we were able to measure the degree of penetration quickly and easily, and the accuracy was equivalent to that of the conventional method. In this paper, we explain the functions of the software and show an example of using the software to measure the degree of penetration of our products. This result is important because it will lead to the improvement of the quality control and the productivity of work.
Y Susa, D Watanabe, T Shigeyama, Y Sugai

Development of Wooden Fireproof Structures for Mid- and High-rise Buildings in Japan
2021 - IRG/WP 21-30757
When constructing a mid-to-high-rise building more than 4 stories in general in Japan, it is necessary to have a fireproof structure stipulated by the Building Standard Law. The performance required as a fireproof structure in Japan is generally stricter than in other countries, and it is required to be structurally sound after a fire even without fire extinguishing activities. In order to satisfy this requirement, the structural member must continue to support the load during the event of a fire. In the case of wooden structure, this means that the combustion should be eliminated spontaneously, and the charring of load support portion is not allowed. Under these conditions, many wooden fireproof structures have already been developed, and wooden buildings are actually being constructed widely. The method of making a wooden fireproof structure is roughly divided into (1) a “inorganic covering type” with gypsum board and (2) a “flame die out type” using fire-retardant treated wood or heat absorbing material. In this report, we will introduce these wood-based fireproof structures, as well as the fireproof structure of “flame die out type” developed by our research group, and the cases where the wooden fireproof structure has been actually applied to various buildings.
D Kamikawa, M Harada, H Matsunaga, R Takase, N Hattori, Keisuke Ando, M Miyabayashi

Mechanical and biological durability properties against soft-rot and subterranean termite in the field (grave-yard test) of beech wood impregnated with different derivatives of glycerol or polyglycerol and maleic anhydride followed by thermal modification in an opened or in a closed system
2021 - IRG/WP 21-40917
This paper presents mechanical and biological durability properties in soil beg test (soft-rot test) and field test (grave-yard test) against subterranean termite of the wood modified with an aqueous vinylic derivative of glycerol/polyglycerol or maleic anhydride cured in an opened or in a closed system. Wood modification was performed through impregnation of European beech (Fagus sylvatica) with aqueous solution of polyglycerol maleate, glycerol maleate, or maleic anhydride at 10 or 20% w/w concentration, followed with curing under oven heating (OHT) at 120°C, 150°C, or 220°C in opened system or under heat pressurised steam (HPS) at 150°C in closed system. The modified woods were then characterized for their weight percent gain and mass losses after curing process, mechanical properties [modulus of elasticity (MOE), modulus of rupture (MOR), work to maximum load in bending (WMLB)], and biological durability properties against soft-rotting micro fungi in soil beg test and against subterranean termite (grave-yard test) in a tropical country. Results have revealed that almost all modified wood presented higher MOE values than untreated wood, however, MOR and WMLB decreased up to 27% and 87%, respectively. Biological durability in the soil beg test against soft-rot indicated that almost all modified wood were specified as durable to very durable wood. However, among the treatments, the wood modified with polyglycerol maleate/glycerol maleate/maleic anhydride at 20% under OHT 150°C or the wood modified at lower additive concentration (10%) under OHT 220°C presented significantly better durability against subterranean termite within a period of 328 days in the field.
M Mubarok, H Militz, S Dumarcay, I W Darmawan, Y S Hadi, P Gerardin

Estimation of residual compressive strength on cross laminated timber with biodeterioration damage
2021 - IRG/WP 21-40918
CLT is susceptible to biodeterioration such as fungal decay and termite attack during long-term use for buildings. It is necessary to know the residual strength performance of biodegraded CLT for estimating future performance and aging of CLT. In this study, compression tests of CLT damaged by brown rot fungi and termites were conducted to clarify the relationship between residual strength and mass loss rate. The relationship between strength and defect rate of effective area (parallel layer’s area) calculated from CT scan data was also investigated. As a result, it was found that there is a negative correlation between the defect rate of the effective area and the strength, regardless of whether the deterioration factor is decay or termites, and this relationship may be used to estimate the residual strength. In the case of termite-damaged specimens, a low correlation was found between residual stress and mass loss rate, suggesting that it is difficult to estimate residual strength from the mass loss.
R Inoue, T Mori, K Kambara, W Ohmura

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