Microwave reflectometric tool for non-destructive assessment of decay on timber structures

Timber structures can be degraded during their life both by structural problems and, mainly, by biological degradation factors like fungi, and insects (Coleoptera and termites). The occurrence of these biodegradation agents leads, in the absence of appropriate maintenance interventions, to the loss of their structural integrity. Furthermore, if these biological agents decay old buildings, the loss of mechanical resistance of timber structures can be added to loss of cultural heritages. Just in these contexts an early evaluation of decay is crucial to design remedial treatments and a less invasive restoration intervention. This work presents a new microwave diagnostic system for the in situ evaluation of timber structures based on microwave reflectometry, i.e on the measurement of the microwave reflection coefficient as a function of frequency. The continuous-wave (CW) microwave signal is launched by a double-ridged antenna, which also measures the wave reflected by the material under investigation. The measurement system allows diagnosing the effects of biodegradation during a first quick survey in a non-destructive and non-invasive manner. Measurements on laboratory models demonstrated the feasibility of the method. Results obtained on timber beam sections, compared with the findings of traditional investigation methodologies, demonstrate the potentiality of microwave reflectometry, suggesting its usefulness for decay detection and as a support to invasive diagnostic tools.