Assessing the Ability of Ground-Penetrating Radar to Detect Fungal Decay in Douglas-Fir Beams

This paper describes the testing plan and current progress for assessing the efficacy of using ground-penetrating radar (GPR) to detect fungal decay within Douglas-fir beams. Initially, the beams were assessed using a variety of physical, mechanical, and nondestructive evaluation (NDE) test methods including micro-resistance drilling, Janka hardness, ultrasonic transmission, and GPR. After initial baseline assessment, beams were inoculated with brown rot fungus, Fomitopsis pinicola, and exposed to above-ground conditions approximately 25 miles (40 km) north of Gulfport, Mississippi, USA. Beam specimens will be removed from the exposure site at six-month intervals and scanned using GPR to detect and assess interior rot. After GPR scanning, micro-resistance drilling and ultrasonic transmission testing will be performed. Finally, the beams will be cut into 2-in. segments for Janka hardness testing, which will give the most definitive information regarding the spread of the brown rot fungus throughout the beams. The GPR scans will be compared to the hardness testing, micro-resistance drilling, and ultrasonic testing results to evaluate the ability of GPR to detect interior rot within the beams.

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