| The mechanical properties of wood are very sensitive to wood decay, but accuracy and reproducibility problems have limited its use in wood decay tests. To address these problems, a modified method of evaluating wood preservatives in an accelerated soil contact test was explored using small decay cups containing unsterile soil and thin (3mm) pine sticks. It was found that the decay rate was rapid, with significant decay being detectable in untreated wood after two months exposure. The extent of wood decay was measured by monitoring changes in the bending elasticity (MOE) of the test samples, which was found to be a sensitive measure of the decay rate for both CCA and CuNap treated as well as untreated wood. The rate of wood decay in both treated and untreated wood samples was accelerated when the soil was amended with wood compost. Use of amended soil also resulted in significantly higher copper depletion rates for CCA treated wood, but not for the CuNap treated wood.; It was also found that in this study that the MOE of 3mm thick southern yellow pine sticks decreased slightly after three bending cycles with a deflection of 2mm, which is under the proportional limit of the sticks. This finding is in contrast to a general understanding that MOE is not compromized when the deflection is less than the proportional limit. It was also found that sterilizing the sticks by autoclaving resulted in a decrease in MOE of approximately 10%, but no further change was observed when the sticks were repeatedly deflected for six cycles. For decayed sticks, there was only a slight decrease in MOE when they were repeatedly bent for six cycles after the decay was arrested. The proportional limit of the decayed sticks subjected to 2mm deflection was not exceeded until the decay advanced to an MOE loss about 40-50%.; Wafer distribution schemes were explored for a new soil block decay test which uses compression strength to determine the extent of wood decay. The results showed that randomized complete block distribution minimized variation. |
