Flexural Reinforcment of Timber Elements on-Site With PRF Adhesive and Wood-Based Products

Abstract

In this study, the potential application of a two-component phenol-resorcinol-formaldehyde adhesive for on-site reinforcement of glued laminated timber (GLT) and a recovered spruce beam was investigated. Different spread rates (500 -2000 g/m 2 ), means of pressurization of the bond lines (clamps, screws and the reinforcements own mass) were applied to establish bond lines between the substrate to be reinforced and the reinforcements, GLT and plywood (PLW). The surface conditions (not planed, partly coated/ sanded, varying surface moisture content) were chosen to resemble situations that might be encountered during on-site reinforcement. The bond lines of two of the 11 different combinations fulfilled the required shear strength according to EN 14080. The investigations show that thicker bond lines and low pressure on the bond lines result in lower bond strength. Coating and partial removal of the coating by sanding are expected to have amplified the effect of the chemically weak boundary layer. Bond lines between materials with similar surfaces yield higher shear strength compared to bond lines between materials with differing surfaces.