Evaluating the durability of structural glulam bonded with aqueous polymer-isocyanate adhesive by two kinds of accelerated aging treatments

Glued laminated timber (glulam) is widely used in building construction and is required to have high durability as a structural member. A decrease in adhesion properties induces the delamination of glulam and declines its mechanical properties. Aqueous polymer-isocyanate adhesive (API) is relatively new in terms of structural applications, and there is little information available regarding the durability of glulam laminated by the glue. In this study, two different cyclic accelerated aging treatments were used to assess the durability of API bonded glulam consisting of sugi, hinoki and spruce. The durability was estimated by a change in shear strength. In both accelerated aging treatments, the wood failure percentage of glulam did not decrease although the shear strength declined. Thus, it was assumed that the decrease in shear strength was affected by wood cracks rather than deterioration of adhesives. Additionally, the durability of API bonded glulam, resorcinol formaldehyde resin (RF) bonded glulam, and solid wood was compared using a deterioration model. Eventually it was presumed that API bonded glulam had high durability equal to or greater than solid wood and RF bonded glulam when exposed to a cyclic wet-dry treatment.