STUDIO DEGLI EFFETTI DELL’ACCOPPIAMENTO GALVANICO TRA ARMATURE ZINCATE E CASSERI METALLICI NEL CALCESTRUZZO FRESCO

In the present work, the phenomenon of hydrogen evolution on the surface of the steel moulds, used to obtain concrete manufactured products reinforced with galvanized rebars, has been investigated. The galvanic coupling between the moulds and the galvanized reinforcements, in the fresh concrete just after the cast, leads to a large amount of hydrogen bubbles evolution on the external surface of the manufactured product, which will be characterized by a high roughness. In many cases, it can be a problem for manufacturers of these products. In order to study this phenomenon and to evaluate it quantitatively, a formwork in a reduced scale was built for simulating a prefabricated real beam. It was equipped with a mould formed by "segmented" steel walls of which, by means of an electric circuit suitably realized, the partial currents and local potentials for each segment were measured. Furthermore, the potential and the current of the macrocouple relative to the galvanized bars were also monitored. From the electrochemical measurements and the observations made on the surface of the manufactured product at the end of the experimentation, it was found that the hydrogen evolution mainly affects the area of the mould directly facing the galvanized bars, leading to a significant roughness of the concrete surface in contact with this area.