Concrete: Durable through History (and then some)
Concrete is known for its strength, low cost and especially its durability. All three are well earned, but none more than the durability of concrete. There is a building in Yugoslavia made from concrete that is still standing – almost 8,000 years after it was built! Many ancient civilizations knew of the wonders of concrete, though they may not have known what made it work. The techniques and the ingredients have remained surprisingly similar over the millennia from the time when the ancients mixed stone dust with water.
Build like an Egyptian
The ancient Egyptians were pioneering in their use of synthetic building materials, using crushed lime and gypsum mixed with water and various aggregates to make building materials and decorative sculptures. They were famous for their use of clay, whether for building structures, pots, religious figures or any other number of uses.
However, recently there have been suggestions that the Egyptians may have used concrete for some of their most famous structures, including the Pyramids. Traditionally archaeologists have maintained that the pyramids are constructed entirely of limestone blocks that were quarried offsite and then laboriously brought to the construction site. Some archeologists are now claiming that some of the blocks, specifically the supporting structures and the upper blocks where it would be incredibly difficult to raise the immensely heavy limestone blocks, are made from concrete blocks made with limestone cement.
When in Rome
Walk through Rome today and you will see structures that were made from concrete during the height of the Roman Empire, many of which are still standing in close to perfect condition. The Romans perfected the use of pozzolana cement, made from stone quarried in Pozzuoli, Italy. Many of the most famous buildings of Rome were made from cement, such as the Pantheon, the Appian Way, many Roman baths and quite a few aqueducts that were built across the empire to convey water to the city. Lime was used as the main ingredient to create the cement, with various aggregates such as sand or the aforementioned pozzolana.
The Romans were very creative with their use of admixtures to make the cement stronger, lighter and longer lasting. Some of the most popular additions were animal fat, milk and blood.
The Lost Art
Like many of the techniques of the arts and sciences, the use of concrete as a building material was largely lost after the fall of Rome. Throughout the Middle Ages, some of the largest and most ornate cathedrals, mosques and churches were built across Europe and the Middle East. However, the builders almost exclusively used quarried stone that was cut to fit the structure as needed. Concrete was used as a mortar to build the religious buildings, as well as many castles and other large edifices, but not rediscovered as a primary building material until the 18th and 19th centuries. In the early 19th century, portland cement reintroduced concrete into mainstream construction and it has remained a common building material ever since.