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The importance of renewable and environmentally acceptable materials in the construction industry is increasing. Wood is one of the most important construction materials and its use in building applications has further expanded in recent decades, mainly due to the development of modern composites, firstly glue lam, OSB (Oriented Strand Board), LVL (Laminated Veneer Lumber) and a considerable breakthrough was later achieved with the development of cross-laminated timber. In order to enable even more extensive and reliable use of wood in outdoor applications, factors affecting a wood’s service life need to be understood. It is well known that fungal degradation of wood is predominantly affected by temperature and wood moisture content. In order to elucidate the influence of these two factors, long-term monitoring of temperature, relative humidity and moisture content at the newly-built Annex of the Department of Wood Science and Technology was carried out. The Annex is designed from CLT composites and glue-lam beams and was finished in December 2015. The results clearly show that microclimatic conditions in the monitored building in the first years of use are far below the limit required for fungal decay or mould growth.

Wood is a traditional roofing material in Europe and other parts of the world. In the seventeenth century, wooden roofing was generally used on more important buildings, but today it is mainly used on huts and houses in the Alpine regions. As wooden roofing is expensive, we investigated the possibility of extending the service life of the roofing through material selection and details. The roof of the Golobar cable yarding was covered with shingles made of spruce (Picea abies) and larch (Larix decidua). Part of the spruce roofing was thermally modified and/or treated with a water-wax emulsion. On the underside, we cut grooves in selected roof shingles to increase the specific surface of the wood and to accelerate drying after rainfall. In addition, wood moisture monitoring sensors were installed on the roof shingles. Based on three years of the wood moisture content measurements, it can be concluded that among shingles made of untreated spruce wood, the highest moisture content was recorded for shingles with a rectangular cross-section without additional grooves. The additional grooves positively affected the moisture performance of wood. Treating the wood with Silvacera wax had an even more pronounced effect on the moisture content of the shingles than the grooves. Nasl. z nasl. zaslona. Objavljeno 17. 4. 2023. Opis vira z dne 19. 4. 2023. Bibliografija.

Wood is one of the most important building materials. Thermally modified wood is entering the market and replacing wood preservatives and tropical wood species in some applications. 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. Moisture performance reflects the material’s ability to remain dry and dry out fast when wet. The aim of this study was to determine whether this phenomenon is associated with crack formation 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. This may be associated with Wenzel’s theory on the influence of roughness on the contact angles of water on the surface; namely, increased roughness will decrease the contact angle on hydrophilic surfaces.

Les na prostem je izpostavljen delovanju abiotskih in biotskih dejavnikov. Če hočemo njihovo delovanje upočasniti, moramo les zaščititi. V preteklosti je bil biocidni proizvod na osnovi bakrovih, kromovih in borovih spojin (CCB) ena najpomembnejših rešitev za zaščito lesa v ostrih pogojih izpostavitve. Kljub temu, da se CCB v EU praktično ne uporablja več, lahko služi kot referenca za vrednotenje novih biocidnih proizvodov. Na terenskem polju Oddelka za lesarstvo Biotehniške fakultete že 14 let poteka poskus v realnih pogojih, kjer so impregnirani vzorci izpostavljeni vremenskim vplivom v skladu z dvoslojnim testom. Pri zaščitenem lesu pogosto opažamo, da les propade hitreje kot je pričakovano. V okviru tega prispevka želimo na podlagi analize razkrojenega s CCB impregniranega lesa s terenskega polja Oddelka za lesarstvo ugotoviti, zakaj je prišlo do prezgodnjega razkroja. Rezultati kažejo, da ustrezno življenjsko dobo zagotavljata ustrezna retencija in penetracija aktivnih učinkovin v les.

Wood in outdoor applications is exposed to various environmental factors that cause weathering. Weathering is important, primarily from an aesthetic standpoint and predominantly in wooden claddings. However, not all parts of claddings are equally exposed to weathering. Sections exposed to UV radiation and moisture discolour faster than less exposed sections, such as wood under roof overhangs. Architects and owners seek a uniform appearance in buildings. To achieve fast and uniform greying, a surface treatment with iron(II) sulphate can be used. Such a treatment results in an appearance that is similar to that resulting from natural greying. However, iron compounds do not exert a biocidal effect; therefore, it is desirable to upgrade iron(II) sulphate aqueous solution with boric acid and quarterly ammonium compounds. To this end, spruce and larch samples were treated with varying concentrations of iron(II) sulphate and biocides. After treatment, the inherent durability, water performance and resistance dose (DRd) were determined according to the Meyer-Veltrup model. The samples were also exposed outdoor conditions. During exposure, colour changes and iron leaching were monitored. The results show that the addition of biocides does not affect the rate of colour change and the final colour, which is similar to natural greying after 36 weeks of outdoor exposure. The addition of biocides exerted a positive effect on the durability of treated wood, despite the low retention of preservative solutions. The water behaviour of the treated wood had little effect on the resistance dose, with a more considerable influence on inherent durability. The addition of biocides can increase the resistance dose up to 2.4 (Fe5B0.2Q0.2). On all spruce and larch samples treated with iron(II) sulphate and exposed to outdoor conditions, the colour change in the first week was roughly comparable to the final state. However, 40% of the iron had leached from the surface after only one week of exposure. Nasl. iz nasl. zaslona. Opis vira z dne 16. 9. 2022. Št. članka 1497. Bibliografija: str. 16-17. Abstract.

Krožno gospodarstvo in uporaba sekundarnih surovin postajata vedno polj pomembna. Uporaba odsluženega lesa za materialno izrabo je trenutno še zelo slabo izkoriščena. Večino odsluženega lesa se namreč porabi v energetske namene. Eden od potencialnih virov odsluženega lesa so tudi stara lesena okna. Večino oken se v današnjem času zamenja zaradi neustreznih energetskih karakteristik, medem ko je les večine zamenjanih oken še brez znakov razkroja. Težavo pri uporabi lesa odsluženih oken za proizvodnjo novih izdelkov predstavljajo predvsem površinski premazi. V raziskavi smo preverili vpliv starosti, tipa in površinske obdelave na delež onesnažil. Iz okenskih profilov smo najprej odstranili vse nelesne materiale, profile razžagali po debelini, ter s tem preverili, kako globoko v les so prodrla anorganska onesnažila. Les smo analizirali z rentgenskim fluorescenčnim spektrometrom (in določili deleže posameznih anorganskih onesnažil (Cr, Cu, Cl, Fe, Zn, Pb). Rezultati so pokazali, da odslužena okna vsebujejo anorganska onesnažila zgolj na površini (do 5 mm globoko), količine onesnažil močno variirajo glede na starost oken in uporabljeno površinsko zaščito. Raziskava je pokazala, da so odslužena okna lahko surovina za proizvodnjo novih izdelkov in materialov, ob pogoju, da pred uporabo odstranimo površinski sloj.

Forests are under great pressure due to climate changes. It is forecast that the importance of Mediterranean type forests will significantly increase. Among various types of oak species, pubescent oak (Quercus pubescens) will likely gain ecological and economic importance in the region south of Alps. Although this wood species is well known, there are not much data available about chemical properties and durability. A comprehensive analysis of extractives and durability against wood decay fungi was therefore performed. The results of the chemical analysis revealed that heartwood contains up to 20% of the extractives, with considerable amounts of phenols, including a fairly high concentration of Gallic acid (GAc). Anatomical structure, with high frequency of tylosis, resulted in good water exclusion efficacy. The presence of biologically active extractives and superior water exclusion efficacy resulted in good durability, as shown by basidiomycetes tests. Based on the laboratory data, factors that determine the service life of wood were calculated. Data indicate superior performance in above-ground applications.

The performance of the composites is influenced by the service life of input raw wood material and used adhesives. The aim of the study was to assess the durability and mechanical performance of glulam beams treated in a different way (thermally modified and/or treated with copper-based wood preservative) and exposed in an outdoor application. Glulam beams (83 mm × 68 mm × 1100 mm), made of three layers of Norway spruce (Picea abies) with PUR adhesives used have been exposed in use class 3.2 in a horizontal position since 4th November 2016. Part of the specimens was equipped with MC sensors. Every year, the degradation was evaluated visually. The dynamic modulus of elasticity was determined by longitudinal vibration, and the static modulus of elasticity using a 4-point bending test. On the smaller specimens, cut from glulams, compressive strength, delamination, and shear strength of adhesive bonds were determined. After two years of exposure, the results indicate that the performance of glulams is determined by the wood modification and applied wood preservative.

The present study analyses the moisture performance of nine wood species and wood-based materials determined in various laboratory and field trials to identify the method with the highest predictive power and determine the correlation between respective measurements. The moisture performance of wood and wood-based products has been recognised (besides inherent wood resistance) as the second most important parameter contributing to wood service life in above ground applications. Therefore, it is of great commercial importance to understand this phenomenon. In-service moisture monitoring trials can be unacceptably long, but on the other hand, they provide more realistic test conditions than laboratory tests. However, experiments in laboratory conditions enable a high level of reproducibility and are much faster than in-service tests. In order to assess the correlation between various tests, Pearson product moment correlation coefficients were calculated to determine the level of the strength of the linear relationship between the in-service and laboratory trials. Within this paper, it was attempted to identify laboratory methods suitable for quantification of moisture content during outdoor exposure.

Les na prostem je izpostavljen delovanju biotskih in abiotskih dejavnikov razkroja. V naravi so ti procesi zaželeni, kadar pa les uporabljamo v komercialne namene, želimo razkroj čim bolj upočasniti. V primeru razvrednotenja lesa pa moramo lesene elemente zamenjati. Lesene izdelke praviloma menjamo zaradi estetskih razlogov ali nedoseganja tehničnih zahtev. V tem prispevku opisujemo najpomembnejše mehanizme in razloge za razgradnjo lesa na prostem, naravno odpornost lesa in sodobne rešitve za zaščito. Na koncu so predstavljeni ključni rezultati o obnašanju lesa na terasi lesenega modelnega objekta na Oddelku za lesarstvo. Terasa ponazarja podobno izpostavitev kot mostovi, pohodne površine oziroma streha, zato je primerna kot odličen prikaz obnašanja lesa na prostem. In outdoor applications wood is exposed to biotic and abiotic degradation factors. These processes are essential for carbon circulation. However, if wood is used in commercial applications, these processes need to be slowed down as much as possible. When wood is degraded, it has to be replaced. In general, wooden elements are replaced for aesthetic reasons or due to the failure to meet technical requirements. This paper describes the most important mechanisms of wood degradation in outdoor applications. Special emphasis is given to the natural durability of wood and state-of-the-art preservation solutions. In addition, key results on the performance of the wooden on the decking of a study object in Ljubljana are presented. The decking represents a similar exposure to that of bridges, outdoor flooring or roofs, and therefore can be used as a model for the assessment of the performance of wood used outdoors.

Lesene strehe so v Sloveniji tradicionalne. V časih Valvazorja so bile značilne za pomembnejše stavbe, danes pa se uporabljajo predvsem za kritje planšarskih stanov in objektov v hribovitih predelih severozahodne Slovenije. Ker je lesena kritina draga, želimo življenjsko dobo kritine podaljšati z izbiro materiala in izvedbo detajlov. Streho Golobarske žičnice smo pokrili s strešniki, izdelanimi iz lesa smreke (Picea abies) in macesna (Larix decidua). Del smrekovih strešnikov je bil termično modificiran in/ali obdelan z vodno emulzijo voskov. S spodnje strani smo v nekaj strešnikov zarezali utore, s tem povečali površino lesa in pospešili sušenje po padavinskih dogodkih. Na strešnike smo namestili opremo za spremljanje vlažnosti lesa. Na podlagi polletnega spremljanja vlažnosti lesa lahko sklepamo, da utori močno skrajšajo čas, ko je vlažnost strešnikov primerna za razkroj. Še bolje se obnese, če strešnike z utori premažemo z vodno suspenzijo voska. Do podobnih zaključkov lahko pridemo tudi pri termično modificiranem lesu. Wood is a traditional roofing material in Slovenia. In the days of Valvazor, wooden roofing was typically used on more important buildings, but today it is predominately used on huts and houses in the hilly regions of northern and northwestern Slovenia. Because wooden roofing is expensive, we investigated the possiblility of extending the service life of the roofing through material selection and detailing. The roof of the Golobar cable yarding was covered with tiles made of spruce (Picea abies) and larch (Larix decidua). Part of the spruce roofing was thermally modified and/or treated with a water wax emulsion. From the underside, we cut grooves into a few roof tiles to increase the specific surface of the wood and accellerate drying after rainfall events. In addition, wood moisture monitoring sensors were installed on the roof tiles. Based on six months of measurements of the wood moisture content, it can be presumed that the grooves shorten the time when the moisture content of the roof tiles is optimal for fungal degradation. Performance is further increased if the tile surface is coated with an aqueous wax suspension. Similar conclusions can be drawn for thermally modified wood.

The importance of thermal modification is increasing worldwide. Increased use of thermally modified timber (TMT) has resulted in a need for reliable quality control, comprising control of variation of the production within defined limits, allowing third-party control in the case of certification and the regulation of customer complaints and claims. Techniques are thus needed to characterise the modification of quality in terms of improved target properties of TMT during industrial production, and of TMT products that have been in service for an arbitrary time. In this study, we aimed to utilise dynamic vapor sorption (DVS) for this purpose. Norway spruce (Picea abies) and European beech (Fagus sylvatica) samples were thermally modified at different temperatures according to different heat treatment techniques: (1) the Silvapro process based on an initial vacuum, (2) an air heat treatment, whereby samples were wrapped in aluminium foil, (3) thermal modification of wood samples in the ambient atmosphere in a laboratory oven. Wood samples from closed processes were analysed for validation. TMT was characterised with respect to mass loss, colour and density. Mass loss of wood due to modification (MLTM) was correlated with factors derived from DVS analysis. The present DVS measurements suggest that the equilibrium wood moisture content (EMC95% RH), the time to reach 10% wood moisture content (t10% MC), and the elongation factor, c, derived from a logarithmic function, can serve as alternative parameters to characterise the quality of several thermal modification processes. Further studies are recommended using other wood species, different modification processes and further parameters gained from DVS measurements to understand the robustness and the predictive power of the applied technique.

After the durability of wood against wood decay fungi, its water performance is the next most important factor that influences the performance of wood in outdoor, above-ground applications. It is therefore of major importance to optimize methods that are able to predict the moisture behaviour of wood in outdoor applications. In order to elucidate these questions, samples were prepared from European oak (Quercus robur/Q. petraea), sweet chestnut (Castanea sativa), European larch (Larix decidua), Scots pine heartwood and sapwood (Pinus sylvestris), Norway spruce (Picea abies) and beech (Fagus sylvatica). The moisture performance of the samples was altered by thermal modification, wax, oil and biocide treatment. Two types of specimens were prepared; smaller specimens (1.5 × 2.5 × 5.0 cm) were exposed to natural weathering for three periods (9, 18 and 27 months) and subsequently analyzed in the laboratory with various methods (contact angle, short- and long-term water uptake and water vapor uptake). In parallel, bigger specimens (2.5 × 5.0 × 50 cm) were exposed outdoors in a monolayer exposure and equipped with moisture monitoring sensors for 18 months. Water performance of wood could change as a result of weathering, being the most evident at thermally modified wood, where the decrease of the moisture performance was the most evident. The results of the study clearly showed that the water performance of the majority of the materials decreased with natural weathering. These results indicate that in order to elucidate the moisture performance of wood fully, a variety of laboratory tests needs to be applied, relating to both liquid water performance and water vapour interactions with wood.

Thermally modified wood is becoming an increasingly popular material for different applications in buildings. Laboratory tests indicated a positive effect of thermal modification on durability, dim ...

Relevant properties of stone pine (Pinus pinea) wood have been only fragmentarily addressed in the past, which has been recognized as a limiting factor for its potential applications. The sorption properties, permeability to water, extractives content and durability against fungi of Pinus pinea sapwood and heartwood were therefore determined in the present research. A SEM analysis was also performed. The Meyer-Veltrup model for material resistance was used to test relevant data. The results showed that sapwood of P. pinea fits into durability class 5 (very susceptible wood), while heartwood meets the requirements of durability class 2 (durable wood), if the mass loss after fungal exposure is considered as the sole criteria for classification. Heartwood contains up to 15% of lipophilic compounds, contributing to its hydrophobicity and influencing its sorption properties. In contrast, sapwood is very permeable and hence takes up a lot of water, while heartwood, with a higher resin content, exhibits better water performance. The higher durability of stone pine heartwood against wood decaying fungi can be linked to the presence of phenolic extractives and hydrophobic properties.

Wood is one of the most important construction materials and its use in building applications has further expanded in recent decades. In order to enable even more extensive and reliable use of wood in outdoor applications, factors affecting wood’s service life need to be understood. It is well known that fungal degradation of wood is predominantly affected by temperature (T) and moisture content (MC). In order to elucidate the influence of these two factors, long term monitoring of T, relative humidity (RH) and MC at four locations was carried out: a model house made of thermally modified wood in Mozirje (1), the WWII partisan hospital Franja (2), a hayrack in Pokljuka (3) and a house in the north of Slovenia in Vrba (4). The results clearly showed that fungal degradation of wood is influenced by MC and T. In addition, the influence of micro-climatic conditions on fungal decay was shown.

Wood is one of the most important construction materials and its use in building applications has further expanded in recent decades. In order to enable even more extensive and reliable use of wood...

Ten different samples from Slovenian hardware stores were analysed. Samples were treated with copper based wood preservatives that were designed and advertised to be used in heavy duty applications in ground (use classes 4) and above ground (use classes 3.2). Retention and fungicidal properties were determined in order to establish the quality of treatment quality. Retention was determined by XRF analysis, while a modifi ed EN 113 procedure was applied for the assessment of fungicidal properties. Two brown rot fungal species, Gloeophyllum trabeum and Fibroporia vaillantii, were used for durability testing. The results of the analysis clearly showed that only three of the inspected wood products met penetration requirements, and none of them had sufficient retention, which is also reflected in insufficient durability against wood decay fungi., Za potrebe ovog rada analizirano je deset različitih uzoraka iz slovenskih prodavaonica građevnog materijala. Uzorci su tretirani zaštitnim sredstvima na bazi bakra namijenjenim i preporučenim za zahtjevne uvjete primjene u tlu (uporabna klasa 4) i iznad tla (uporabna klasa 3.2). Određeni su retencija i fungicidna svojstva tih sredstava kako bi se utvrdila kakvoća zaštite drva. Retencija zaštitnog sredstva određena je uz pomoć XRF analize, dok je modificirani postupak EN 113 primijenjen za procjenu fungicidnih svojstava zaštitnih sredstava. Za testiranje trajnosti poslužile su dvije vrste gljivica smeđe truleži, Gloeophyllum trabeum i Fibroporia vaillantii. Rezultati analize jasno su pokazali da su samo na tri istraživana drvna proizvoda bili ispunjeni zahtjevi penetracije zaštitnog sredstva, a ni na jednome drvnom uzorku nije postignuta dovoljna retencija zaštitnog sredstva, što se očituje i nedostatnom trajnošću drva izloženoga djelovanju gljiva truležnica.

Wooden fa&ccedil, ades are gaining in importance. Thermally modified wood is becoming one of the preferred materials for claddings. In spite of the fact that fa&ccedil, ades made of thermally modified wood have been in use for more than two decades, reports about long-term monitoring have been sparse. The results of three-year monitoring of a fa&ccedil, ade made of thermally modified wood in Ljubljana are reported. Moisture content measurements of thermally modified fa&ccedil, ades were taken at 22 locations and compared to the moisture content of untreated Norway spruce wood. Temperature and relative humidity were recorded in parallel. The moisture content of the wood was compared to the average relative humidity before the measurements. The results confirm the lower moisture content of thermally modified wood in comparison to reference Norway spruce. The moisture content of the wooden fa&ccedil, ade could be best correlated with the average relative humidity and temperature 48 h before the wood moisture content measurement was taken.

The performance of the composites is influenced by the service life of input raw wood material and used adhesives. The aim of the study was to assess the durability and mechanical performance of glulam beams treated in a different way (thermally modified and/or treated with copper-based wood preservative) and exposed in an outdoor application. Glulam beams (83 mm × 68 mm × 1100 mm), made of three layers of Norway spruce (Picea abies) with PUR adhesives used have been exposed in use class 3.2 in a horizontal position since 4th November 2016. Part of the specimens was equipped with MC sensors. Every year, the degradation was evaluated visually. The dynamic modulus of elasticity was determined by longitudinal vibration, and the static modulus of elasticity using a 4-point bending test. On the smaller specimens, cut from glulams, compressive strength, delamination, and shear strength of adhesive bonds were determined. After two years of exposure, the results indicate that the performance of glulams is determined by the wood modification and applied wood preservative., Na svojstva kompozita utječu trajnost sirovine i svojstva primijenjenih ljepila. Cilj ovog istraživanja bio je procijeniti trajnost i mehanička svojstva različito obrađenih lameliranih nosača (toplinski modificiranih i/ili impregniranih bakrom) izloženih u eksterijeru. Lamelirani nosači (83 mm × 68 mm × 1100 mm) izrađeni su od tri sloja smrekovine (Picea abies) koji su slijepljeni PUR ljepilom. Nosači su prema klasi uporabe 3.2 izloženi u vodoravnom položaju od 4. studenoga 2016. u trajanju od dvije godine. Na dio uzoraka postavljeni su senzori za mjerenje sadržaja vode u njima. Svake je godine vizualno ocjenjivano propadanje uzoraka. Dinamički modul elastičnosti određen je longitudinalnom vibracijom, a statički modul elastičnosti savijanjem u četiri točke. Na manjim uzorcima ispiljenima od nosača određena je tlačna čvrstoća, delaminacija i čvrstoća lijepljenog spoja na smicanje. Nakon dvije godine rezultati izlaganja pokazali su da svojstva lameliranih nosača ovise o toplinskoj modifikaciji drva i sredstvu za impregniranje.

Thermal modification is the most important commercial modification procedure. Thermally modified (TM) wood has improved durability, but its performance does not meet expectations predominately under moist conditions. To reduce water uptake of TM wood, Norway spruce specimens were treated with suspensions of a natural wax by dipping impregnation (DipI) or by vacuum-pressure impregnation (VPI). Wax-treated specimens were subsequently TM at 185, 200, 215, and 230°C. Control specimens were heated up to 100°C only. Contact angle (CA), short-term and long-term water uptake, bending strength, and performance against wood decay fungi of the resulting material were determined. The results show that a combination of wax treatment and thermal modification have a synergistic effect that considerably improves hydrophobicity, reduces liquid water uptake, slows down water vapor uptake, and improves the resistance against fungal decay of the treated material.