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The Oldest Concrete Structures That Have Lasted
Concrete is a common building material that is used prolifically in the construction of many buildings and infrastructure projects. The strength, durability, and flexibility of this material has added to its popularity. Yet concrete has actually been around since ancient times – some of the oldest buildings that humans created are built with early forms of concrete. These are some of the most impressive and longest-lasting buildings that have been made with concrete.
The Pyramids, Giza, Egypt
One of the first forms of concrete used that still exists today can be found in the Pyramids at Giza, Egypt, which were built around 3,000 BC. While the Pyramids are constructed of bricks made from mud and straw, the mortar used between the bricks was created from gypsum and lime (from heated limestone), which would harden and set much like modern cement mortars.
The Colosseum and Pantheon, Rome, Italy
The Roman Empire was known for their impressive architecture, many of which were built using cement and concrete that is very similar to that used today. To create the mortar used for their concrete, the Romans combined pozzolans (fine volcanic ash, which was readily available in Italy), lime, and water.
To build a load-bearing wall, they created rudimentary formwork using wood, stacked rocks, or bricks – or a combination of these – onto which they laid a layer of aggregates or broken bricks. The pozzolan mortar was then poured into the form and tamped to consolidate the concrete. Layer by layer, the process was repeated until the wall or slab was completed. Interestingly, the higher layers used lighter-weight aggregates to reduce the weight of the concrete – travertine was used for the foundation layers, while light tuff and pumice were used for higher layers.
Both the Colosseum and Pantheon are excellent examples of the longevity and adaptability of concrete. The Colosseum has concrete vaults, and also uses a cement mortar made from limestone and clay for between the bricks. The Colosseum was completed in 80 A.D., having taken ten years to build.
Meanwhile, the Roman Pantheon boasts the largest unreinforced solid concrete dome in the world, with a diameter of 43.4m. Built between 126-128 A.D., this is an impressive record to have held for nearly 2,000 years, particularly when considering that the dome does not use steel concrete reinforcement or any supports. In fact, the clear span of the dome was not substantially surpassed until the adoption of steel reinforced concrete, according to the research of David Moore, P.E.
Eddystone Lighthouse, Cornwall, UK
While these early forms of concrete had been used in ancient times, the art of making concrete fell out of favour and this construction method was not used again for many years until the mid-eighteenth century. John Smeaton, a British civil engineer, undertook extensive testing of various limes available at the time. Through his research, he discovered that the hydraulicity of lime was related to different minerals which were either present in the limestone or added, such as pozzolans. He combined this hydraulic lime with powdered brick and pebbles to create the first form of modern concrete, which was used to build the Eddystone Lighthouse in 1759 along with stone masonry. The benefit of Smeaton’s hydraulic lime was that the mortar and concrete set rapidly despite the wet conditions of the site. This early research led to the invention of modern-day Portland cement. Developed in 1824 by Joseph Aspdin of England, it quickly became the dominant cement used in construction.
72 rue Charles Michels, St. Denis, France
In 1853, François Coignet – a French industrialist – built a four-storey house in St. Denis, France. While Coignet had previously built unreinforced concrete houses – many of which are still standing today – the building at 72 rue Charles Michels was the world’s first reinforced concrete structure. The building uses iron reinforcement as opposed to steel, and whilst currently empty, the building has been listed as a French historic monument since 1998.
Alvord Lake Bridge, San Francisco, USA
This bridge was the first reinforced concrete bridge to be built in the USA, having been constructed in 1889 by Ernest L. Ransome. This structure uses steel reinforcing bars and survived the 1906 San Francisco earthquake and many others as well, and can still be found within the Golden Gate Park today. Ransome invented his own reinforcement, which took the form of square bars made of cold-twisted steel. These bars are embedded within the underside of the arch and are bent to the same curved profile. The Alvord Lake Bridge features a 29-foot-long (8.84-metre) span; however, by the 1900s, reinforced concrete bridges were being built with spans of 100 feet (30.58 metres) or more.
Court Street, Bellefontaine, USA
Located along the local courthouse’s southern face is the first and oldest concrete street in the USA. Court Street was built in 1891 in Bellefontaine, Ohio and is still in service today. Although the first concrete pavement in the world was first built in Inverness, Scotland in 1865 and parts of this road are still in use, Court Street is noteworthy for its high strength. Tests showed the pavement achieved a breaking strength of 8,000 pounds per square inch (55MPa), which is much stronger than the majority of concrete used today.
The Ingalls Building, Cincinnati, USA
Built in 1903, the Ingalls Building was the world’s first reinforced concrete high-rise building. Boasting 16 storeys, the structure is 180 feet (54 metres) tall, which was a feat of engineering for the time. The lower strength and stiffness of concrete in comparison to steel meant that building tall structures in concrete was difficult, particularly before the elastic theory of structures was developed for reinforced concrete.
Warren LeMay from Cincinnati, OH, United States, CC0, via Wikimedia Commons
Centennial Hall, Wroclaw, Poland
The Centennial Hall in Wrocław, Poland (then Breslau, Germany) was built in 1913 of reinforced concrete. Designed by the architect Max Berg, the hall features a reinforced concrete dome with a span of 65 metres (216 feet). Today, the hall has been designated a World Heritage site, with many visitors each year.
Concrete Stands the Test of Time
With structures thousands of years old, even before the invention of modern forms of concrete, it’s clear that concrete is a durable and long-lasting material. With concrete structures, the question is not so much, will it last, but rather, how long will it last? If these structures are any indication, the answer could be: much longer than anyone expected.