Adhesive bond performance of historic casein-bonded glued-laminated beams

Abstract

An historic 1934 building on the campus of the U.S. Department of Agriculture, Forest Service, Forest Products Laboratory was deconstructed in 2010. The glued-laminated (glulam) beams from the building were preserved, creating a unique opportunity to test the casein adhesive bonding in the beams that had been in service for more than 75 years. The goal of the testing reported in this study was to extend the understanding of protein adhesives in wood products. In this study, we tested wet and dry strength of the bonds using compressive block shear tests. We also tested for delamination and looked at bond strength in bending over a range of temperatures in a dynamic mechanical analyzer. We found that the dry strength of the glulam adhesive tested in compressive block shear was very good. All the bonds failed in the wet strength testing. Because of the rigorous standards used for the delamination testing, all the beams failed the delamination testing, but surprisingly, about one-third of the beams showed only a small amount of delamination. From the dynamic mechanical analysis thermal scans, we saw little change in stiffness at higher temperatures, which suggests that the casein adhesive retained its elevated temperature strength even after 75 years.

Citation

O’Dell, Jane L.; Hasburgh, Laura E.; Frihart, Charles R. 2025. Adhesive bond performance of historic casein-bonded glued-laminated beams. Res. Pap. FPL-RP-724. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 10 p. https://doi.org/10.2737/FPL-RP-724.