Pre-applicable structural adhesives for timber engineering: Glued-in G-FRP rods

Abstract Glued-in-rods represent a particular class of adhesively bonded joints increasingly being used in civil engineering, and in which load is transmitted from timber elements by means of rods through a layer of adhesive. As such they share with all adhesively bonded connections the issues that are associated to adhesives. Commonly used adhesives for glued-in rods in timber engineering, cold curing 2C epoxies or polyurethanes, only harden relatively slowly, which makes this joint type tributary to costly and time consuming temporarily fixing systems, and their handling on site is still relatively cumbersome. In order to simplify bonding of glued-in rods on site, the potential of pre-applicable adhesives are combined with inductive heating. Pre-applicable structural adhesives are adhesives that can be applied on parts, then stored for weeks or months, and subsequently triggered to achieve adhesive and cohesive strength. The pre-applicable structural adhesive investigated in this research (PASA®) can achieve full cure by supplying thermal energy, which for the case investigated herein has been provided by induction. Because of the non-metallic nature of the FRP rods induction was achieved by mixing metallic particles to the adhesive. The combination of both techniques proved functional, and has the potential to simplify the use of glued-in rods for timber engineering, e.g. by using flexible inductors wrapped around the timber members.