Corrosion of Metallic Fasteners in Timber-Concrete Composite Structures

While Timber-Concrete Composite (TCC) construction has been intensively studied in terms of structural behaviour, there is little research on the risk of corrosion of the used metallic shear fasteners in different exposure environments. Due to the marked differences in chemical environments of wood and concrete, however, it can be expected that the fasteners are subject to galvanic corrosion. This was experimentally studied in the present work. TCC specimens were fabricated for electrochemical testing and exposed to two different exposure environments, that is, 95% relative humidity and immersion in water. The moisture content in the wood, the difference in electrochemical potentials and the galvanic current were monitored over 2 months. Two types of fasteners were tested, namely zinc galvanized steel fasteners as well as browned fasteners that have been widely used in the TCC construction industry since 2013. It was found that the fastener parts in the wood generally act as an anode, while the remaining parts in the concrete act as a cathode. However, significant galvanic currents were only observed upon immersion in water. For practical applications in structural engineering, it is concluded that the mass loss of metal of the studied fasteners cannot present a severe risk for structures, especially not at the service classes 1 and 2 according to EN 1995-1-1.