An X-ray µCT assessment of fungal degradation in poplar-CLT

Abstract Poplar wood is increasingly recognized as a promising material for engineered wood products (EWPs) such as cross-laminated timber (CLT) due to its favourable strength-to-weight ratio, rapid growth, and cost-effectiveness. While most studies focused on mechanical strength and fire safety of poplar CLT, little attention has been given to its biological durability, particularly resistance to fungal decay. This study evaluates the degradation behaviour of thermally modified (TM) and untreated poplar CLT under controlled fungal tests with Trametes versicolor and Rhodonia placenta . X-ray micro-computed tomography (µCT) was used to monitor density changes and internal degradation patterns in three-layer CLT over 21 weeks. Sealing played a critical role in durability by limiting fungal ingress and moisture uptake through the end grain: sealed samples showed <5 % mass loss and, as revealed by X-ray µCT, density increases mainly from moisture uptake, whereas unsealed samples lost 20–25 % and exhibited clear degradation. Thermal modification further restricted fungal penetration, with minimal density loss compared to untreated poplar. These findings highlight the importance of moisture management and protective measures for poplar CLT service life and demonstrate the potential of X-ray µCT as a tool for non-destructive analysis of fungal degradation in wood.