Detection of fungal decay by high-energy multiple impact (HEMI) testing

Abstract

Abstract The suitability of a previously described high-energy multiple impact (HEMI) test for the detection of early fungal decay was examined. The HEMI test characterises the treatment severity of thermally modified wood by stressing the treated material by thousands of impacts of pounding steel balls. This method differentiates between heat treatment intensities, which are manifest as structural changes in the wood. Similar changes in wood structure are known for wood decayed by fungi. Pine (Pinus sylvestris L.) decayed by brown rot and beech (Fagus sylvatica L.) decayed by white rot were tested. Mass loss caused by fungal decay and resistance to impact milling (RIM) determined in HEMI tests were found to be highly correlated. Testing of non-degraded pine, beech, and ash (Fraxinus exelsior L.) showed only marginal effects of wood density on RIM. Furthermore, annual ring angles and RIM of spruce (Picea abies Karst.) were not correlated. Accordingly, the detection of RIM reduction in decayed wood is not masked by variations in density and orientation of the annual rings. Previous results showed no adverse effects of weathering on RIM. Thus, the detection of fungal decay with HEMI tests is feasible not only for laboratory purposes, but also for wood in outdoor applications that has already undergone weathering.