Effects of Postlayup Borate Treatment on Appearance and Flexural Properties of Douglas-Fir Glued Laminated Beams

摘要

Preservative treatments are required whenever glued laminated beams are exposed outdoors. Treatments can be either water-based systems applied to individual laminations prior to layup or organic solvent–borne systems applied after the beams are fabricated. Water-based systems are not recommended for posttreatment because of concerns over checking and the potential for reductions in flexural properties, but there are few data on the effects of these treatments. The effects of pressure treatment with disodium octaborate tetrahydrate (boron) on flexural properties, glue-line shear, and visual appearance were investigated using Douglas-fir (Pseudotsuga menziesii) glued laminated beams. While treatment did result in the presence of drying checks on some beams, boron treatment followed by air seasoning or mild kiln drying did not produce any significant effects on modulus of rupture, modulus of elasticity, or glue-line shear. The results indicate that boron treatment does not affect load-bearing properties.