Assessment of the Long-term Shear Behavior of Epoxy Polymer Lap Joint Used to Bond Steel and Concrete Composite Structure

This article presents the results of an experimental study concerning the evolution in time of the shear modulus of an epoxy resin used for bonding together steel girders and concrete slabs. For this purpose, two experimental methodologies are set up. The first one, based on mechanical spectroscopy measurements allows to assess a rheological model adapted to the polymer resin (Zener's model). In this case, the analysis of the shear behavior of the material itself is carried out. The second one, based on the time-temperature equivalency principle, analyzes the long-term shear behavior of epoxy joints under real loading conditions: double shear tests are performed on steel-concrete lap joint bonded together with an epoxy adhesive. The results of the two procedures permit to assess the evolution of the shear modulus for a time period of 10(9) s (approximate to 50 years). Analyzing only the intrinsic behavior of the material is insufficient for this time range, because additional mechanisms occur at the concrete-epoxy interface.