Concrete can be found in historical monuments in essentially three different forms:
• as a substitute material or structural reinforcement material in stone buildings (such as the concrete structure of the Reims cathedral, and the reinforcement structure of the Strasbourg cathedral spire),
• as a construction material, in a wide variety of buildings: housing blocks, churches, industrial or military heritage sites (for example, the Cité Radieuse housing block in Marseille, the Saint-Christophe de Javel church in Paris),
• and as ornamental material (examples include the bas-reliefs of the Saint-Esprit church in Paris and the concrete windows of the Sacré-Cœur church in Audincourt). The main deterioration mechanism in old concrete is the carbonation phenomenon; it is considered a natural aging process of concrete, due to contact with CO2 in the air, which triggers corrosion of the concrete’s reinforcement.
Two areas of research have been developed by the Concrete section over the last few years:
• the study of how best to preserve aging concrete, whether in the form of cleaning, elimination of biological deposits, addressing the corrosion of steel reinforcing bars or desalination;
• the study of diagnostic techniques for corrosion of steel within old concrete.