sentences:  From the digging of ancient Roman ruins, one knows that approximately 95% of the concretes and mortars constituting the Roman buildings consist of a very simple lime cement, which hardened slowly through the precipitating action of carbon dioxide CO2, from the atmosphere and formation of calcium silicate hydrate (C-S-H).This is a very weak to medium good material that was used essentially in the making of foundations and in buildings for the populace.But for the building of their "ouvrages d’art", especially works related to water storage (cisterns, aqueducts), the Roman architects did not hesitate to use more sophisticated and expensive ingredients.