The recipe for Roman concrete was described around 30 BC. C. by Marco Vitruvius Pollio, engineer of Octavian, who became Emperor Augustus. This not-so-secret ingredient was volcanic ash, which the Romans combined with lime to form mortar.
This material, known as opus caementicium, was used in construction in Ancient Rome and was based on a hydraulically setting cement. It is durable due to its incorporation of pozzolanic ash, which prevents cracks from spreading. By the middle of the 1st century, it was frequently used, often with brick cladding, although variations in aggregate allowed different material arrangements. Other innovative developments in the material, called the concrete revolution, contributed to structurally complicated forms, such as the Pantheon Dome, the largest and oldest unreinforced concrete dome in the world.
The precursor of concrete was invented around 1300 BC. C., when builders in the Middle East discovered that when they coated the exterior of their fortresses with crushed clay and the walls of their houses with a thin, wet layer of burnt limestone, it chemically reacted with gases in the air to form a hard, protective surface. This was not concrete, but it was the beginning of cement development. Roman concrete consists of an aggregate and a hydraulic mortar, a binder mixed with water that hardens over time.
When combined with aggregate materials and water and allowed to harden, cement is now extraordinarily strong. These mixed cements also produce C-A-S-H, but their long-term performance could not be determined until Monteiro's team analyzed the Roman concrete. Built by Emperor Hadrian of Rome and completed in AD 125. C., the Pantheon has the largest unreinforced concrete dome ever built. Five years later, Ransome built the Lake Alvord Bridge in Golden Gate Park, the world's first reinforced concrete bridge.
Jackson and his colleagues have been studying the chemical composition of concrete made with Pozzolane Rosse. In addition to being more durable than Portland cement, Roman concrete also seems to be more sustainable to produce. After the fall of the Roman Empire in 476 AD. C., techniques for making pozzolanic cement were lost until the discovery in 1414 of manuscripts describing these techniques reignited interest in building with concrete. Recent research by American and Italian scientists has shown that the concrete used to make Roman ports in the Mediterranean was stronger than modern concrete (known as Portland cement).
Probably the most accomplished person when it came to building with concrete shell techniques was Felix Candela, a Spanish mathematician-engineer-architect who practiced mainly in Mexico City.Composed of aggregate and a two-part cementitious system, it differs significantly from modern concrete. These minerals, similar to the crystals of volcanic rocks, formed intertwined plates in voids within the old concrete, making it stronger over time. The period of time during which concrete was invented depends on how the term “concrete” is interpreted. He analyzed the chemistry of the ruins of four sites along Italy's Mediterranean coast, discovering that Roman concrete was made from rare volcanic ash, minerals, lime and pieces of volcanic rock.