Wood density is a key property since it is affecting almost every other wood property such as elasto-mechanical, acoustic, thermal, or electrical properties (e.g. Nelson and Tra-belsi 2012, Jhatial et al. 2017, Pang and Jeong 2019, Nabipour and Akhoundi 2021). Hence, it is essential to determine wood density for the interpretation of any other property test. Density measurements are usually carried out gravimetrically by measuring the wood specimens’ dimensions and taking their weight. In order to be independent of the moisture, wood density is measured at an absolute dry state, i.e., the oven-dry state with a wood moisture content (MC) of 0 %. According to different standards (e.g. ASTM D4442:2020, EN 13183-1:2022), the wood specimens shall be dried at 103 °C until constant weight, cooled in a desiccator, and weighed with a defined accuracy depending on the wood specimens size and mass. However, depending on which wood properties shall be measured after the oven-dry density is determined, heating the wood up to 103 °C can be problematic because volatile components of the wood can evaporate. The ingredients lost in this way may not only falsify the density determination itself, but also the results of subsequent tests such as durability experiments.
This study aimed at examining, which drying conditions (temperature in °C, duration in h) are required to achieve the oven-dry state inside the test specimens of choice. The latter was studied depending on the wood species and specimen format representing different volumes and ratios between end grain and side grain surfaces and the volumes of the specimens.
Keywords: absolute dry density, durability testing, evaporation, wood-water relationship
Authors
Lukas Emmerich
Wald und Holz NRW – Centre of Forest and Wood Industry, Team Wood-Based Industries, Olsberg, Germany
Moritz Kampherm
Wood Biology and Wood Products, Faculty of Forest Sciences and Forest Ecology, University of Goettingen
Christian Brischke
Thünen Institute of Wood Research, Hamburg, Germany
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