Non-destructive evaluation of moisture content of wood material at GPR frequency

Non-destructive evaluation of moisture content in wood using ground-penetrating radar

“…The increase of relative permittivity versus moisture content is piecewise linear, with a slope change occurring when the humidity level is about 18 %, in agreement with a previous publication where more samples were considered (Mai et al, 2015).…”

“…Moreover, the slope strongly depends on the polarisation of the electromagnetic field and this is in agreement with Martínez-Sala et al (2013b), Mai et al (2015). When the electric field is orthogonal to the wood fibres, a slope change occurs at a humidity level of about 18 %, corresponding to the fibre saturation point.…”

“…A preliminary example of application of the direct-wave approach to wood assessment can be found in Mai et al (2015). In that paper, tests were carried out on a sample of spruce with a humidity of 12 %.…”

“…In Lualdi et al (2003), Muller (2003), Sbartaï (2011), Martínez-Sala et al (2013b, Mai et al (2015), the properties of wood were estimated using reflected-wave methods. In Lualdi et al (2003), GPR was used to detect timber beams and evaluate the type and size of their connection to a bearing wall.…”

“…However, when the field propagated in a random direction, the electromagnetic parameters did not differ significantly. In Mai et al (2015), laboratory measurements were carried out with the aim of studying the sensitivity of electromagneticwave propagation to moisture variation and fibre direction, in spruce and pine wood samples. The relative permittivity (dielectric constant) was measured using the resonance technique at 1.26 GHz, and results were compared to GPR measurements carried out with a 1.5 GHz ground-coupled antenna.…”