Most likely it was not (just) supreme architectural skills and good fortune that made the Trajan Forum last for almost 20 centuries, but volcanic ashes in the mortar used by the ancient Roman builders. X-ray analysis of a wall sample from the Trajan’s Market ruins in Rome showed that the mortars used by ancient Romans contained stratlingite, a mineral known to strengthen modern cements.
The cement used by Apollodorus of Damuscus’ builders to construct the huge ancient roman complex contained sandy ash of a volcano that erupted 456,000 years ago.
To find the ash they turned to the material erupted from the Alban Hills volcano some 456,000 years ago. The area features three pozzolanic (cement-like) deposits, known as Pozzolane Rosse, Pozzolane Nere and Pozzolanelle. “Of these, the type that makes a harsh, grating, rasping noise when rubbed vigorously in the hand is best,” the ancient Roman writer and architect Vitruvius wrote in his De Architectura, a 10-volume treatise on architecture.
Find more information on this at the Discovery.com website.