Assessment of wood decay in small-scale unsterile soil-bed tests
IRG/WP 97-20111
L Machek, A M Derksen, R Sierra-Alvarez
This study is concerned with the investigation of wood decay in small-scale unsterile soil-bed tests. Tests were performed with untreated heartwood samples from five hardwood species of different natural durability classes ranging from highly perishable to very resistant. Our results confirmed the critical role of soil moisture content on wood decay. The highest decay rates were observed at moisture levels close to the soil water holding capacity (WHC). With all the wood species tested, decay was retarded in soils with lower or higher moisture contents. Modification of the soil properties by addition of different amounts of an inert porous material did not affect the extent of wood decay provided that the moisture content of the modified soils was maintained, in each case, at their respective WHC. Test performed with mini-stakes (5 x 10 x 100 mm3) and smaller mini-blocks (5 x 10 x 20 mm3) showed similar levels of decay, irregardless of the test specimen size. In both cases, high mass and modulus of elasticity losses were observed in the highly perishable to moderately durable wood species after only 12-18 weeks of exposure. Based on the extent of wood decay, the small-scale soil-bed test was found to successfully discriminate between wood species in different natural durability classes.