Balsam fir strength behavior at moisture content in service after freezing in green condition

Abstract

In northern countries, engineered wood products are widely used for the construction industry. Recently, a concern has been raised regarding a slow freezing rate in green wood (of the order of 1 °C / h up to 25 °C) that could greatly reduce wood strength. Thus, logs processed during winter might produce lumber with a lower mechanical strength in service than those produced during summer. Therefore, the main objective of this study was to evaluate the influence of the freezing rate on the selected mechanical properties of balsam fir (Abies balsamea [L.] Mill). Three groups of 17 planks (20 mm x 20 mm x 1200 mm) were exposed to three freezing rates (10 °C/h, 5 °C/h, 1 °C/h) and another group was kept as a control group. After the freezing treatments, the planks were stored in a conditioning room at 20 °C and 65% relative humidity to obtain an equilibrium moisture content of 14%. Samples of 10 mm x 10 mm x 190 mm and 10 mm x 10 mm x 40 mm, for static bending and parallel compression to the grain tests were then prepared, respectively. The results showed that the freezing rate did not have any effect on the mechanical strength of balsam fir wood.