Evaluation of Bonding Durability for Wood Preservative Treated Glulam by Accelerated Aging Test and Outdoor Exposure Test I. Bonding durability evaluated by accelerated aging test

Abstract

In order to correlate bonding durability obtained from accelerated aging tests (AAT) and outdoor exposure tests, and to investigate the influence of wood preservatives, resorcinol content, specimen width and specimen density on bonding durability of glulam, we manufactured 5 ply sugi glulams with laminae treated with five wood-preservatives (ACQ, E-NCU, E-CUAZ2, NZN, AAC). Block shear form specimens of 10 mm and 25 mm width were taken from those glulams, and specimens were subjected to cyclic-boiling (C-B) or cyclic-vacuum-pressure (C-VP) of 2, 5, 10, and 20 cycles respectively, followed by block shear tests. We defined the wood failure area for which we could not confirm an adhesive layer as “deep wood failure”, and calculated the deep wood failure ratio. The decrease of shear strength at C-B was larger than that of C-VP. The results of statistical tests showed that the degree of decrease of shear strength did not correspond to the differences of shear strength observed among wood preservatives. Though shear strength of 25 mm width specimens showed higher values than those of 10 mm width before AAT, after AAT 10 mm width specimens showed higher values and less decrease of shear strength than those of 25 mm width. It was assumed that the reason was that stresses occurring at the adhesive layer or wood for 10 mm width specimens were lower than those for 25 mm width. High density specimens showed higher shear strength before AAT; however, those differences tended to diminish after AAT. In most cases phenol-resorcinol resin adhesive showed higher shear strength than resorcinol resin adhesive. Wood failure ratio did not show remarkable differences, and deep wood failure ratio increased remarkably after two cycles of AAT. © 2011, The Japan Wood Research Society. All rights reserved.