A system for continuous measurements and long-term recording of wood moisture content has been developed to be implemented in durability field tests. Based on the electrical resistance of wood measurements were conducted using conductively glued electrodes and miniature data logger. Material-specific resistance characteristics were determined for a wide range of native timber species, thermally and chemically modified timbers as well as for timber impregnated with various wood preservatives. The system was thus calibrated in a range between 15 and 50 % wood moisture content. The electrical conductivity was significantly affected by the wood species, the type and intensity of cell wall modification and preservative impregnation respectively. However, moisture content measurements were possible for all materials in question with an overall satisfying accuracy for moisture contents above 15%. The measurement system has been applied to estimate the moisture load under different test conditions, the moisture performance of various wood-based materials, as well as the test-site specific severity of exposure. The system turned out to be a useful tool for determining the time of wetness that occurred on tested wood-based materials under outdoor exposure. However, the results pointed on the need to determine resistance characteristics for every single material under test to assure high reliability. Some limitations need to be considered when wood is treated to varying extents.
Keywords: decay, modified timber, resistance, service life prediction, wood durability
Authors
Meyer L.
Inst. of Vocational Sciences in the Building Trade (IBW), Faculty of Architecture
Landscape Sciences, Leibniz University Hannover, Hannover
Brischke C.
Inst. of Vocational Sciences in the Building Trade (IBW), Faculty of Architecture and Landscape Sciences, Leibniz University Hannover, Hannover
Lampen S.C.
Inst. of Vocational Sciences in the Building Trade (IBW), Faculty of Architecture and Landscape Sciences, Leibniz University Hannover, Hannover
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