Wood used outdoors is generally prone to fungal degradation, and its impact on the structural integrity of wood is an immanent factor for service life planning with timber. Wood decayed to very small mass losses can suffer from a significant reduction in mechanical strength and elastic properties. Hence, the latter are preferred indicators to detect decay in wood durability studies. Numerous previous studies suggested, for instance, modulus of elasticity (MOE) measurements for decay detection since they outperform mass loss in terms of sensitivity. However, literature reports on the topic are not always consistent and partly contradictory. Therefore, this study aimed at 1.) comparing different methods for decay detection with respect to their sensitivity to decay and transferability to each other, and at 2.) quantifying the effect of white and brown rot decay on bending properties of wood. Generally, with increasing mass loss (ML) due to fungal decay bending properties were negatively affected, and brown rot caused more severe damage to elasto-mechanical properties than white rot decay. The elasto-mechanical bending properties were more sensitive to fungal decay than ML but suffered from remarkably high variation. Temporal and spatial distribution of decay affected the structural stability of wood, which became manifested in MOE and MOR (modulus of rapture). Particularly, decay pockets and end-grain decay led to significant ML but had little to no effect on bending properties of the specimens. The quality of correlation between auxiliary quantities such as ML and the underlying target properties strongly depends on the experimental set-up. In the study at hand, wood specimens were placed directly on fully developed mycelium and the total specimen volume was subjected to fungal degradation. The transferability of decay assessment data from one method to the other appeared rather limited. The ML, MOE loss and MOR loss data obtained from recent tests should be considered preliminary but may serve to better define limit states which are essential for decay modelling and service life planning.

Download document (734 kb)
free for the members of IRG. Available if purchased.

Purchase this document