Feasibility of using heat treated wood for cross laminated timber production

In this study, the possibilities of using heat treated wood materials in the production of cross laminating timber (CLT) were investigated. For the triple-layer CLT panel study, Scots pine (Pinus slyvestris Lipsky) and Uludağ fir (Abies bornmülleriana Mattf.) wood species were used. Among all the layers, polyurethane glue were preferred in all test types, while in some upper layers pretreated with silane primer. Furthermore, in the upper layers, heat treated wood material is placed in some experiment types. In these materials, shear resistance in tension, shear resistance in bending, modulus of elasticity in bending, and internal bonding strength tests were carried out. In addition, the color change of the heat treated material was also investigated. In accordance with the results of the experiment and the results obtained from the eight experiments, it was determined that the solid control (non-heat treated) CLT material treated with the silane liner was found strongest from the heat treated CLT material (whether or not using the silane liner in the top panel). Nevertheless, when compared with the heat-treated and only polyurethane-glued test samples and the heat treated CLT test samples using silane primer; for shear resistance in bending 14% decrease for Scots pine and 25% decrease for Uludağ fir was observed; for modulus of elasticity in bending it was found that 7% decrease in Scots pine and 5,8% decrease in Uludağ fir were found in the test samples using heat treated with silane primer. On the other hand, regarding the internal bonding strength values, for Scots pine samples it was decreased by 35%, while Uludağ fir it was increased by 10% with heat treated CLT samples pretreated with silane primer. According to the results, heat treatment causes decrease on shear strength in tension by 24% on Scots pine control specimens and 3,9% on Uludağ fir control specimens. However, silane pretreatment improved the shear strength in heat treated Scots pine specimens by 4,8% but there is a decrease on heat treated Uludağ fir specimens by 13%. Statistical analysis (ANOVA and Tukey's) showed that there is no significant difference was found among groups. Compared to solid (control) CLT test type and heat treated CLT test types for both tree types, the heat treatment reduces the values of shear resistance and internal bonding strength, and shear resistance and modulus of elasticity in bending values were found to be close to each other. For silane pretreated solid (control) CLT samples; shear resistance, shear modulus and shear resistance to the surface were increased. As a result; it has been found that the heat treated specimens reduce the mechanical properties of the CLT material compared to the solid (non-heat treated) test specimens. In addition, the use of silane pretreatment in solid wood (non-heat treated) production of CLT has resulted in a wood structure panel with high durability and better load carrying capacity.