Use of fire-impacted trees for oriented strandboards

This study evaluates the potential use of currently unexploited burnt timber from prescribed burns and wildfires for oriented strandboard (OSB). The research was performed in two phases: in Phase I, the effect of thermal exposure of timber on OSB properties was evaluated. Jack pine (Pinus banksiana) trees variously damaged by a moderately intense prescribed burn in a northern Wisconsin forest were selected. Four fire-damage levels of wood were defined and processed into series of single-layer OSB. The flakes used in Phase I had all char removed. Mechanical and physical properties were evaluated in accordance with ASTM D 1037. Results showed that OSB engineering performance of all four fire-damage levels were similar, and their mechanical properties met the CSA 0437 requirements. In Phase II, we assessed OSB properties from fire-killed, fire-affected and virgin red pine (Pinus resinosa) trees from a central Wisconsin forest exposed to an intense wildfire. The effect of various thermal exposures and varying amounts of char on OSB performance were evaluated. Phase II findings indicate that fire-damage level and bark amount had significant effects on the board properties. Addition of 20 percent charred bark had an adverse effect on bending strength; however, OSB mechanical properties still met the CSA requirements for all fire levels. Conversely, bark addition up to 20 percent was found to improve dimension stability of boards. This study suggests that burnt timber is a promising alternative bio-feedstock for commercial OSB production.