1,721,418 research outputs found
Impact of fungal decay on the structural integrity of wood
No full textAbstract Wood-destroying fungi induce different types of decay, which cause significant reductions in elastomechanical properties of wood when the mass loss is not yet gravimetrically detectable. Particularly difficult to define is incipient decay since the reduction of elastomechanical properties is highly dependent on the heterogeneity of wood species. Early-stage effects of incipient decay on impact behavior remain insufficiently understood. The aim of this study was to clarify how different rot types affect structural integrity in relation to mass loss. Therefore European beech ( Fagus sylvatica ) and Scots pine ( Pinus sylvestris ) sapwood specimens were incubated with white-rot ( Trametes versicolor ), brown-rot ( Coniophora puteana ) or soft-rot fungi. After incubation, moisture content and relative mass loss were measured. Mass loss (ML) increased linearly over time across all fungi-wood combinations, reaching a maximal reduction of 67% in European beech wood and 39% in Scots pine sapwood with Trametes versicolor . For Coniophora puteana , ML in European beech peaked at 26%, while Scots pine sapwood reached 24%. Soft-rot fungi caused the least degradation reaching 9% ML for European beech wood and 4% for Scots pine sapwood after 99 days. High-Energy Multiple Impact (HEMI) – tests were performed to evaluate the effect of mass loss by fungal decay on the structural integrity of wood, expressed as the Resistance to Impact Milling (RIM). The RIM decreased with increasing ML at early-stages proving the high sensitivity of the test to detect incipient decay, especially with brown rot. The reduction of structural integrity was compared with the reduction of different strength properties of wood depending on the mass loss, where RIM values exhibited less variability compared to other strength properties, suggesting higher measurement stability in case of white and brown-rot decay
Decay resistance of wood treated with amino-silicone compounds
No full textAn amino-silicone (AS; amino-polydimethylsiloxane) micro-emulsion was tested for its suitability to preserve wood against basidiomycetes in a mini-block experiment and in a test according to the European standard (1996) EN 113. Decay resistance was assessed against the white rot fungi Trametes versicolor, Ceriporiopsis subvermispora, and Hypoxylon fragiforme, as well as the brown rot fungi Coniophora puteana, Antrodia vaillantii, Gloeophyllum trabeum and Serpula lacrymans. Pine sapwood and beech wood were treated with AS emulsions at solute concentration levels of 2%, 5% and 15%. The mini-blocks treated with 15% concentrations of AS resisted decay by T versicolor and C. puteana over a long time (12 weeks), while samples treated with low and moderate concentrations underwent considerable mass losses. Accordingly, microscopic studies revealed a high degree of colonisation by the white rot fungus and loss of cell wall integrity (brown rot) in samples treated with 2% AS. At high AS content (15%), no or only initial stages of decay could be observed. In the European standard (1996) test EN 113, the mass loss in all fungal cultures except for the white rot ascomycete H. fragiforme was below 5%, when the samples were treated with 15% AS. The effect of low and moderate AS concentration on the decay resistance was dependent on the fungal strain. The mode of action of AS treatment against basidiomycete decay is discussed
The Performance of Wood Decking after Five Years of Exposure: Verification of the Combined Effect of Wetting Ability and Durability
No full textWood is one of the most important construction materials, and its use in building applications has increased in recent decades. In order to enable even more extensive and reliable use of wood, we need to understand the factors affecting wood’s service life. A new concept for characterizing the durability of wood-based materials and for predicting the service life of wood has recently been proposed, based on material-inherent protective properties, moisture performance, and the climate- and design-induced exposure dose of wooden structures. This approach was validated on the decking of a model house in Ljubljana that was constructed in October 2013. The decay and moisture content of decking elements were regularly monitored. In addition, the resistance dose DRd, as the product of the critical dose Dcrit, and two factors taking into account the wetting ability of wood (kwa) and its inherent durability (kinh), were determined in the laboratory. DRd correlated well with the decay rates of the decking of the model house. Furthermore, the positive effect of thermal modification and water-repellent treatments on the outdoor performance of the examined materials was evident, as well as the synergistic effects between moisture performance and inherent durability
Studies on the material resistance and moisture dynamics of Common juniper, English yew, Black cherry, and Rowan
No full text
Monitoring in Forestry and Wood product chain: book of abstracts of the Scientific meeting Forest and Wood, [Ljubljana, May 19th, 2015]
No full textDurability of wood exposed above ground - experience with the bundle test method
Full text linkThe durability against decay organisms is an essential material property for wood in outdoor use. A jack of all trades method for above-ground wood durability testing has been sought for decades, but until now no method has found its way into European standardization. The method of choice shall be applicable for untreated and treated wood—ideally also for wood composites. It shall further be reproducible, objective, fast, easy, and inexpensive. Finally, it shall provide high predictive power. This study was aimed at a review of results and practical experience with the Bundle test method which could serve as a standard procedure for above-ground field tests of wood-based materials. The method allows for water-trapping, creates a moderate moisture-induced decay risk typical for UC 3 situations, and was found applicable for a wide range of wood materials. The method allows for rapid infestation and failure of non-durable reference species within five years in Central Europe. Based on results from Bundle tests with different modifications and performed at different locations, a guideline has been developed. The method is recommended as a suitable tool for determining the durability of various wood-based materials including modified and preservative-treated wood and can provide data for durability classificatio
Thermal modification of bark beetle damaged spruce wood
Full text linkZaradi velikih količin manj vrednega pomodrelega lesa, nas zanima, ali lahko takemu lesu dvignemo dodano vrednost s postopkom termične modifikacije. Pomodrele in kontrolne vzorce smrekovine smo modificirali pri dveh temperaturah in na njih izvedli več testov. Zanimala nas je izguba mase po modifikaciji, sprememba barve, tlačna trdnost, upogibna trdnost, stični kot, kratkotrajni in dolgotrajni navzem tekoče vode ter sorpcijske lastnosti. Testi so pokazali, da ima modificiran pomodrel les malo slabše mehanske lastnosti kot nepomodrel. Vse ostale, za termično modificiran les bolj pomembne lastnosti, pa so se izboljšale. Stični kot se je pomodrelim vzorcem po termični modifikaciji znatno povečal, na kontrolne vzorce pa ni imel bistvenega vpliva. Na kratkotrajni in dolgotrajni navzem vode je imela termična modifikacija velik vpliv. Navzem pomodrelih in kontrolnih vzorcev se je zmanjšal na primerljivo vrednost. Termična modifikacija je izboljšala tudi sorpcijske lastnostiravnovesna vlažnost vseh vzorcev je padla, povečala pa se je tudi sposobnost oddajanja vlage oz. sušenja. Celotna serija poskusov nam je pokazala, da lahko s termično modifikacijo pomodrel les znatno izboljšamo in mu tako dvignemo dodano vrednost.Due to large quantities of blue stained wood with low market value, we aimed to determine whether we can increase its market value with the process of thermal modification. Blue stained and control samples were thermally modified at two different temperatures. A series of tests were then performed. Mass loss, colour change, compressive strength, bending strength, contact angle, short-term and long-term liquid water uptake, and sorption properties were determined. Results have shown that thermally modified wood has deteriorated mechanical properties, but all the other properties have improved with the process of thermal modification. Thermal modification significantly improved contact angle of blue stained specimens, whereas control specimens remained more or less the same. Same goes for short-term and long-term water uptake, both of which performed poorly prior to thermal modification compared to control specimens. Thermal modification improved the blue stained specimens to the point, where the results were comparable to control specimens. Equilibrium moisture content of all thermally modified specimens decreased. Drying velocity was also improved by thermal modification. The series of the performed tests showed that it is possible to improve blue stained wood\u27s properties with thermal modification and therefore greatly increasing its market value
Possibilities of remediation of soils polluted with nitrogen compounds
Full text linkTla postanejo onesnažena z dušikovimi spojinami s prekomerno uporabo gnojil in fosilnih goriv. Visoka koncentracija teh spojin (predvsem nitrata) povzroča nižanje pH vrednosti tal. Posledično se iz tal okrepi izluževanje esencialnih elementov. Po drugi strani se poveča tudi mobilnost toksičnih elementov (npr. Al). Zaradi zaostrenih življenjskih pogojev se zmanjša stopnja biodiverzitete v zemlji, kar vpliva na rast rastlin (dreves, poljščin…). Obstaja pester nabor možnosti remediacije tal. Te vključujejo fizikalno-kemične principe ter tehnike bioremediacije. Proces denitrifikacije bakterij in gliv v atmosfero sprošča inerten N2 in N2O, ki pripomore k močnejšim podnebnim spremembam. Na zakisana območja se lahko posadijo na nizko vrednost pH naravno tolerantne rastline. Potencial za odstranjevanje dušikovih spojin predstavljajo tudi gensko spremenjene rastline s prekomerno gensko ekspresijo nekaterih ključnih metabolnih encimov. Simbiotski odnosi med mikroorganizmi in rastlinami omogočajo lažje preživetje in večjo uspešnost v okolju pri obeh straneh. Dodatek bio-oglja v zemljo izboljša njene lastnosti ter rastlinam in zemeljskim mikroorganizmom omogoči boljše pogoje za obstoj. Za učinkoviti metodi za odstranjevanje nitrata sta se izkazali tudi remediacija s pomočjo električne energije ter upravljanje nivoja podtalnice, pri kateri se ustvarijo primerni pogoji za denitrifikacijo.Soils become polluted with nitrogen compounds through excessive use of fertilizers and fossil fuels. High concentrations of these compounds (mostly nitrates) cause a decrease in soil pH. As a result, the elements that are needed by the plants are excluded from the soils. The mobility of toxic elements (e.g. Al) increases. Because of the less favourable living conditions the soil biodiversity decreases. There is a diverse range of soil remediation options. These include the physicochemical principles and bioremediation techniques. The process of denitrification of bacteria and fungi releases inert N2 and N2O, which contributes to stronger climate changes, into the atmosphere. Acidic areas can be planted with naturally tolerant plants. The potential for the removal of nitrogen compounds is also represented by genetically modified plants that possess gene overexpression of the key metabolic enzymes. Symbiotic relationships between microorganisms and plants allow easier survival and greater environmental performance on both sides. Adding bio-char to the soil improves its properties and plants along with the terrestrial microorganisms have better chances of survival. Remediation with electrical energy and groundwater level management with which are created conditions for denitrification, have also been proven efficient for the nitrate removal
Analysis of the reasons for the degradation of impregnated wooden posts
Full text linkLes v zadnjem času pridobiva na veljavi kot gradbeni material. Ko ga uporabljamo za gradbene namene, želimo, da lesni izdelki čim dlje časa obdržijo funkcionalnost. Še posebej zunaj vgrajen les je izpostavljen lesnim škodljivcem, če pa je poleg tega še v stiku z zemljo, pa je ogroženost še večja. Leseni koli, ki smo jih preučevali v diplomskem projektu so bili zabiti v zemljo na otroškem igrišču v Ljubljani. Kljub impregnaciji z bakrovimi pripravki so delno strohneli že po petih letih. V primeru neustrezne zaščite je trajnost impregniranega lesa povsem primerljiva z nezaščitenim lesom. Vizualna analiza kolov je potrdila, da so bili razkrojeni z glivami rjave trohnobe. Iz trhlih kolov smo pripravili dve vrsti vzorcev. Prvi so bili za določanje vsebnosti bakra v lesu in drugi za določanje tlačne trdnosti. Vsebnost bakra v lesu smo analizirali z napravo Oxford instruments XRF analyser, tlačno trdnost pa z Univerzalnim testirnim strojem Zwick-Roell Z100. Prišli smo do spoznanja, da so bili koli slabo impregnirani in so vsebovali premalo bakra, zato so v kratkem obdobju izgubili veliko tlačne trdnosti.Importance of wood as building material is increasing. When we use it for construction purposes, we want to retain its mechanical properties as long as possible. Used outdoor, wood is exposed to wood deterioration agentsin ground contact its exposure is even more threatning. The researched wooden posts were applied in the ground at the playground in Ljubljana. Despite the fact that they were impregnated with a Cu preparation, they were completely degraded after 5 years. Their service life was thus comparable to service life of untreated wood. Wood posts were degraded by brown-rot fungi. 2 kinds of samples were prepared from investigated posts used for determination of Cu content and compressive strength. The results clearly show that wood posts were poorly impregnated. Mechanical properties degraded in quite short time
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