Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2008
Sammendrag
An easier penetrability and a more even uptake of wood protection agents is aimed for the two most common wood species in Europe, namely Norway spruce (Picea abies) and Scots pine heartwood (Pinus sylvestris), particularly when there is a great difference in absorption behavior of sapwood and heartwood. Microwave conditioning can improve permeability, reduce density and heat conductivity and change dimensional stability of wood. It could also improve the permeability of refractory wood species. This study deals with the evaluation of different parameters of a microwave treatment and their influence on the penetrability of water during dipping and impregnation of Scots pine heartwood and Norway spruce. Microwave irradiation lead to an increased water uptake after a submersion test, and after vacuum and pressure impregnation of the tested samples. This effect was more pronounced for Scots pine heartwood samples than for spruce wood samples. A short process with high microwave energy is recommended in order to reduce the development of large cracks but to increase the sorption behavior due to small checks in wood.
Sammendrag
Wood is a unique building material, but is by nature designed to deteriorate. A detailed understanding of the factors and interactions involved are important when working with service life prediction of wooden components in buildings. Wood may experience exponential fungal degradation caused by variation in the climatic factors within a small limited area and by minor imperfection in the wooden component. In this paper we put forward a new term: critical in-situ conditions (CIC). This is meant to bring the attention to the importance of looking into details in the construction design, the specific climatic factors and interactions involved. Gaining realistic and useful data for prediction of service life is only possible by controlling and understanding the factors that are target specific for a wooden component or even only a part of it. Performing measurements in a right way and in the proper part of the wooden component are vital for getting useful data for further processing. The objective in this paper is to exemplify the CIC in inservice situations and to describe the factors and interactions that control the service life. Case studies were performed on a building at Bryggen in Bergen, on a hunting cabin on Svalbard, on several wooden windows in the southern part of Norway and on an external wall of a residence house in Ås.
Sammendrag
The area of wood protection is in a period of change. New wood protection systems have been developed while their mode of action remains insufficiently understood. The development of molecular methods provides potential tools to investigate the interaction between modified wood and decay fungi. One small step to tackle some of the unsolved questions about the mode of action of modified wood is taken in this study. A specific and quantitative real-time PCR (QRT-PCR) assay was now established for identifying and quantifying early stages of fungal colonisation in modified wood and for profiling growth dynamics of the white-rot fungus Trametes versicolor through different stages of decay. QRT-PCR of colonisation of three different wood modification systems (acetylation, furfurylation, thermal modification), two reference treatments (Cu-HDO, CCA) and Scots pine sapwood as control was performed. Incubation time was 2, 4, 6, 8 and 10 weeks...
Sammendrag
In Norway exterior wood structures have traditionally nearly exclusively been made of treated and untreated Picea abies and Pinus sylvestris. In recent years there has been a tendency that other tree species, like various domestic hardwoods and imported species have been used in exterior above ground applications, often unfinished. For several wood species, especially hardwoods, information regarding the durability in use class 3 is lacking. The main objective of this paper is to evaluate natural durability of Norwegian wood species for above ground applications comparing two non-standard above ground tests with the European standard tests for soil contact (EN 252) and lab performance against basidiomycetes (EN 113). The European standard tests EN 113 and EN 252 gave quite similar results, and they also corresponded well with the natural durability classification in EN 350-2. The two non-standard above ground tests differed to some extend from EN 113, EN 252 and EN 350-2. The results indicate that natural durability classification for one single wood species can change depending on use class. However, the field trials need a longer period of time before a final classification can be performed. Four species not included in EN 350-2 were classified in this study: Juniperus communis (1), Salix caprea (5), Sorbus aucuparia (5) and Populus tremula (5).
Sammendrag
In this study, the effect of two boric acid concentrations (1% and 2%) and four derivates of tall oil with varying chemical composition were tested separately and in combination. The tall oil derivates were chosen in a way that they consist of different amounts of free fatty, resin acids and neutral compounds. Decay tests using two brown rot fungi (Postia placenta and Coniophora puteana) were performed on both unleached and leached test samples. Boric acid showed a low weight loss in test samples when exposed to fungal decay before leaching, but no effect after leaching...
Foredrag – Decking - surface and system treatments
Gry Alfredsen, Bjørn Jacobsen, Fred G. Evans, ...
Sammendrag
Wood for outdoor decking has a high marked share in the Nordic and Baltic countries among private house owners. Important issues for the consumer are maintenance intervals and aesthetic appearance as well as decay resistance. Knowledge and consumer information about these aspects are required to ensure that wood can compete with alternative decking materials. In this paper an accelerated testing of decking, “stapelbäddsmetoden”, was evaluated after six years of exposure at Ås, Norway, and compared with earlier reported results after three years. Twelve different preservatives and wood modification treatments were used in addition to untreated Scots pine (sapwood and heartwood) and larch (heartwood). The samples were treated with two different surface treatments. In addition there was one set without any surface treatment. In this method for accelerated testing, discolouration and decay was evaluated. This provided new information about performance both on and above ground for a range of different combinations of preservative/modified systems and surface treatments of wood in decking for outdoor use. For example, no clear differences were found between the surface treatments and no surface treatment. The wood modifications with styrene and furfurylalcohol performed just as good, or better, than the copper containing treatments.
Sammendrag
Ved hjelp av elektriske signaler måler den nyutviklete råtedetektoren Rotfinder, rotråte i stående grantrær. Målingene er hurtige og ikkedestruktive. Treets elek triske egenskaper forandres ved angrep av råte. Metallioner frigjøres og fører til at motstanden i treet blir mindre. Det er dette som utnyttes ved målinger med Rotfinder.
Sammendrag
In Norway, exterior wood structures have traditionally, nearly exclusively been made of untreated Norway spruce (Picea abies (L.) Karst) and pressure treated Scots pine (Pinus sylvestris L.). In recent years there has been a tendency that other wood species, like various Norwegian hardwoods or imported species, have been used in exterior above ground applications, often not surface treated. For several wood species, especially hardwoods, information regarding the durability in use class 3 is limited. Most information given in EN 350 part 2 is based on testing of the heartwood in ground contact. The test procedures for above ground test prescribed in European standards, both laboratory and field tests, have some weaknesses regarding natural durability testing. Hence, some new methods for accelerated above ground testing have been put forward. The main objectives of this project are to evaluate natural durability of Norwegian and some imported wood species for above ground applications, and to study various methods for assessing decay in wood. The project material and methods used in the project, and the results from double layer tests after one year of exposure has earlier been described, Flæte et al. (2006). This paper presents the results of the weight and MOE loss in small samples after about 3 years exposure above ground.
Sammendrag
The treatability of Scots pine (Pinus sylvestris) sapwood is ranked in the European standard EN 350-2 as class 1 (easy to treat), although huge differences in sapwood penetration exist. To obtain full sapwood penetration, process parameters have to be adjusted to the material most difficult to treat. It is therefore of importance to understand the factors that are responsible for penetration differences. Scots pine sapwood was investigated for anatomical differences influencing the ratio of filling (RoF) when treated with the wood modifying agent furfuryl alcohol. The database for the study was samples from two test series including Scots pine from Norway and Denmark. Within these experimental series each sample can be reassigned to its original position in the stem. The RoF for each sample was evaluated, and the variation in treatability within trees, between trees and between different stands was studied...
Sammendrag
The inhibitory effect of methanol bark extracts from six deciduous and three coniferous European tree species were bioassayed against eight fungi from the different damage categories, brown rot, white rot, canker and blue-stain. This is the first report providing data on the antifungal activity of several Europaen tree species against fungi within these damage categories. Generally the decay fungi were more inhibited by the bark extracts than the blue-stain fungi, while the lowest inhibition was found among the cancer fungi. The main pattern found between the fungal groups in relation to the bark extracts in this study is believed to be caused by the route of ingress. Acer platanoides bark extract proved to be the most effcient bark extract tested, significantly reducing the growth rate of all tested fungi. Betula pubescens bark extract generally gave the weakest reduction in growth rate. In this study, the conifer bark extracts were in general more active against the canker and blue stain ascomycete fungi than the deciduous trees extracts.