Thin Concrete Shell. Repair and maintenance strategies

After the Second World War, structural research, particularly into thin concrete shells as the final outcome of the evolution of vaulted structures, achieved results that are still unsurpassed. New materials, techniques and methods of calculation supported this typological and expressive innovation characterised by in-depth research into a synthesis between structure and architectural expression. All these researches adopted a highly pragmatic approach to the industrialisation of construction systems, op-timal use of materials and calculation of the structure. The purpose of this paper is to show how these structures, in which research into limits was a fundamen-tal factor, have proved vulnerable to the passing of time and to investigate the reasons why their mainte-nance and repair work require specific strategies. Through a comparative analysis of the maintenance and repairs/restoration of shells built with different construction techniques and found in environments with different levels of aggression, the paper stresses that the issue presents specific variations in relation to the known issues and established modes of intervention in these concrete structures. The decisive factor is that the concrete structure coincides almost completely with the architectural expression, and that to pre-serve its values and meanings the intervention has to be approached with a new logic and methodologies, attentive to the problems of the efficiency of the structure and the durability of the repairs, but also the values of these buildings as a record of the past and the expressiveness of their materials.