Abstract
Aim of study: To obtain improved models to predict, with an error of less than ± 2.0%, the gravimetric moisture content in four different softwoods commonly present in the Spanish and European markets, based on electrical resistance measurements. This improved moisture content estimation is useful not only for assessing the quality of wood products, especially in the case of laminated products, during the transformation and delivery process, but also for accurately monitoring the evolution of moisture in wood present in bridges and buildings, which is of great importance for its maintenance and service life improvement.Area of study: The study was carried out on samples of Scots, laricio, radiata and maritime pines of Spanish provenances.Material and methods: On 50x50x20 mm3 solid wood samples (36 per species, 9 per condition), conditioned at 20ºC (±05ºC) and 40±5%, 65±5%, 80±5% or 90±5% Relative Humidity (RH), electrical resistance and oven-dry moisture content was measured. The Samuelsson's model was fitted to data to explain the relationship between the two variables. The accuracy of the model was evaluated by the use of an external sample.Main results: With the proposed mathematical functions the wood moisture content can be estimated with an error of ±0.9% in the four species, confirming the effectiveness of this nondestructive methodology for accurate estimation and monitoring of moisture content.Research highlights: our results allow the improvement of the moisture content estimation technique by resistance-type methodologies.Keywords: Resistance-type moisture meter; species correction.Abbreviations used: MC: Moisture content; RH: relative Humidity; R: electrical resistance; RP: wood electrical resistance measured parallel to the grain; RT: electrical resistance measured perpendicular (transversally) to the grain; GM-MC: gravimetrically measured moisture content.
Highlights
The moisture content (MC) influences most of the physical, mechanical and technological properties of wood, and affects its quality and service life, especially in constructions
The time to initiation and subsequent rate of wood decay is affected by a series of concomitant factors which make up the so-called ‘‘material climate’’, which in turn has a direct impact on the service life of the wood products and constructions (Brischke et al, 2007)
In order to assess the influence of the species variable, an ANOVA test was carried out for each of the chamber climatic conditions
Summary
The moisture content (MC) influences most of the physical, mechanical and technological properties of wood, and affects its quality and service life, especially in constructions. The time to initiation and subsequent rate of wood decay is affected by a series of concomitant factors which make up the so-called ‘‘material climate’’ (the temperature and moisture content of the wood), which in turn has a direct impact on the service life of the wood products and constructions (Brischke et al, 2007). For this reason, it is vitally important to have moisture and temperature measurement devices which are reliable, safe and precise. Different studies have been carried out (Brischke et al, 2008; Dyken & Kepp, 2010; Tannert et al, 2010 and 2011; Dietsch et al, 2015b; Li et al, 2018; Niklewski et al, 2018) in which both environmental and wood temperature as well as moisture content are monitored, mainly on in-service wood structures (bridges, buildings, etc.) exposed to different climatic conditions and with different design details
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