Moisture transport properties of wood above the fibre saturation point
Ingemar Segerholm
Doctoral thesis “Moisture transport processes in Scots pine. Anomalous capillary suction. Nonisothermal diffusion” (2000) from Civil and Environmental Engineering, Chalmers.
Email: ingemar.segerholm@chalmers.se
Moisture transport in wood is generally regarded to be a well researched area, but there are still controversial issues and unexplored areas. This thesis examines two of these: Capillary suction and nonisothermal diffusion. Both rain and wet snow can bring moisture to building components, with the risk of biological attack. There is a need for models to calculate moisture transport both in the material as such and in building components. What is most important is to develop and test experimental methods. The aim of the project has therefore been to develop simple laboratory methods for the investigation of the transport routes, transport times and long term effects of capillary suction and the temperature effects of moisture diffusion through wood.
Finite element modelling of stress development from tree growth to final timber product
Marie Johansson (project leader)
Summary of results with list of publications from Chalmers.
Email: marie.johansson@konstr.chalmers.se
The most important quality aspect of sawn timber products is a straight and dimensionally stable wood. The shape defects that cause most difficulties in the building industry have different causes. Bowing and springing are due to growth stresses and variation in longitudinal shrinkage within a single batten. Twisting is mainly due to shrinkage together with variation in grain angle and growth ring curvature.
The aim of the project was to construct mathematical models to observe the development of growth stresses in wood and to study how material properties affect the quality of wood in the processing stages. The objective was to develop these models to find how growth stresses and other material properties can be modified through changes in forestry management, sawing and drying for the best possible final product.
Genetic variation for properties that determine the structural quality of spruce timber
Björn Hannrup (project leader)
Summary of results from Forestry Research Institute of Sweden.
Email: bjorn.hannrup@skogforsk.se
Most of the Swedish production of sawn spruce timber products is used in the building sector, where the critical quality parameters are dimensional stability and stiffness. Insufficient dimensional stability is a serious problem in the sawmilling and building industries and has, for example, resulted in large scale replacement of timber studs by steel studs. For structural timber there are warning signals which indicate a very high reduction in the stiffness of wood produced under the production and management conditions of today's silvicultural practices.
The overriding aim was to study the possibilities of improving, by forest tree improvement, the quality of structural spruce timber. In the project, the genetic variation for grain angle, microfibril angle and wood density was studied, and the analysis showed significant genetic variation in these traits. Furthermore, there were strong relationships between the properties of the inner and outer annual rings, i.e. selection based on early measurements will be efficient. It is predicted that selection to increase volume growth by 10% will decrease wood stiffness by 0.6 GPa or 6%. Such negative effects can be counteracted by an active identification and vegetative propagation of clones that combine good growth with acceptable stiffness.
Cleaner wood waste flows from the building sector
Mats Eklund (project leader)
Summary of results with list of publications from Environmental Technology and Management, Linköping University.
Email: mats.eklund@liu.se
Wood waste from the building sector is at present processed into biofuel that is used for the production of district heat. The waste is polluted, which results in increased emission of heavy metals when it is burned. The ashes formed cannot therefore be recycled but must be taken to landfill, which can in time leach into the surrounding environment.
Large quantities of impregnated wood have been used in Sweden to construct fences, terraces and other outdoor timber structures, and the waste gives rise to very large flows of arsenic. Although the law demands that impregnated wood should be treated as hazardous waste, the results show that only 10% is classified as such. Most of it is instead spread in an uncontrolled way. Several technical, organisational and economic obstacles counteract effective separation of polluted wood waste.
The aim of the project was to analyse different ways of handling wood waste. The results show that increased separation of polluted wood waste is advantageous from the environmental standpoint. However, the players in the energy and waste sectors have limited facilities for removing pollutants from the waste. Effective separation must therefore be based on improved separation at source.
There is both a lack of sufficient knowledge and separation also increases the costs of building firms. Owing to lack of communication and supervision, legislation has not had the desired effect. On the other hand, demands by clients have a great potential to create incentives for better separation. In the energy sector, however, because of increased competition for biofuels, quality requirements have not been fully complied with. The waste and building sectors are therefore not exposed to any pressure by their clients to improve separation.
Optimisation of natural antifeedants against the pine weevil by structure activity analysis
Göran Nordlander (project leader)
Summary of results with list of publications from SLU.
Email: Goran.Nordlander@ekol.slu.se
The damage caused by the pine weevil to conifer seedlings costs Swedish forestry hundreds of millions every year. To protect the seedlings, they are routinely treated with insecticides - a treatment that should cease and be replaced by other methods of protection. An alternative is to use substances which, although not toxic, nevertheless stop feeding by the weevil.
The aim was to elucidate the relationship between the chemical structure of various substances and their antifeedant effects. It is envisaged that large quantities of substances with all the desirable properties can be produced by chemical synthesis. The study reveals new possibilities of substantially facilitating the search for optimally active substances. The results show the generality that can be expected, and should be of interest since few previous studies have related to the response of insects to chemical substances.
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