Concrete has a solid history
When we think of discoveries and inventions that have become milestones in the history of mankind, a long list comes to mind. From fire and the round wheel to smartphones and artificial intelligence, countless inventions have changed human lives.
Among such great inventions, there is a rather inconspicuous one that is not talked about as much as the others – a great invention that helped humans build everything from skyscrapers to most of the structures we see in the world today and played a crucial role in the development of civilisation and cultures. The invention we are talking about is concrete.
It is said that concrete is prehistoric. Though not in the form we see today, the use of concrete dates back to the time when humans left caves to build stone houses. In the early days, they used a mixture of mud and clay to fill the gaps between the stone blocks used for building dwellings. This provided protection against the cold and wind, and also increased the durability and reliability of the structures.
Around 6500 BC, the Nabataeans, a class of traders who lived in Syria and Jordan, began to use materials similar to the type of concrete we see today. The walls, floors, and water tanks of the houses were built using a material similar to our modern day concrete. There is evidence that the Egyptians, the Chinese, and the Babylonians carried out construction work using early forms of concrete. In those days, buildings and structures were built by mixing straw with mud. This precursor of concrete was also used in the construction of the pyramids and the Great Wall of China.
The addition of straw ensured mouldability as well as robustness. Limestone mortar was also used in construction during this time.
Researchers have estimated that about 5 million tonnes of limestone was used in the construction of the Great Pyramid of Giza.
Significant changes in the shape and appearance of concrete happened during the time of the Greek Empire.
It is safe to say that concrete as a construction material became ubiquitous by the time of the Roman civilization. The creation of architectural wonders the world marvels at even after 2,000 years happened during this period. Declared by UNESCO as a perfect example of human genius, numerous structures such as the Pont du Gard Aqueduct, the Pantheon, and the Colosseum are symbols of Roman architecture and culture.
Since contemporary engineers guarantee a lifespan of only a hundred or two hundred years for modern-day architecture, it was only natural that research would be undertaken to discover the secret of the longevity of first-century Roman architecture that spans over two millennia. Researchers discovered that the secret of the strength of these historical structures was the composition of the concrete mix used by the Romans for construction.
The main ingredient in Roman concrete was something called Pozzolana ash, which formed after volcanic eruptions. Known as ‘Opus caementicium’ in Latin, this concrete created a revolution during the Roman civilization. It is said that seawater was used in the concrete mix and that many strange things like ponytails and animal fat and blood were added to opus caementicium. However, liable facts regarding the same are not yet available.
With the same kind of concrete, the Romans built roads that could rival their modern counterparts. Many parts of such roads can be seen even today.
The 142-foot-diameter dome of the Pantheon building is made entirely of the same concrete. The Pantheon, believed to have been constructed in 126 AD, remained the largest dome in the world for about 1,300 years until the Italian Renaissance. This Roman dome is the only one that has survived to this day without undergoing any strengthening or other renovations.
By the second half of the 5th century, the Roman Empire collapsed, and it was completely wiped out by 476 AD. The secret of Roman concrete was also lost with the end of the Roman Empire. Opus caementicium and Roman architecture were alien to the world until the discovery of relevant archives in 1414.
John Smeaton, a British engineer, made the concrete mix that is used in construction work today. This important turning point in the history of concrete occurred in 1756, which was 1,800 years after the fall of the Roman Empire. Smeaton, who took charge of the reconstruction of the Eddystone Lighthouse, faced a major challenge.
The cement we see today was developed by an Englishman named Joseph Aspdin. He patented his invention in 1824 as Portland cement.
The first lighthouse was built in 1699 on Eddystone Rocks, about 22 kilometres off the coast of Plymouth in England. It was the first construction of its kind in the world. The lighthouse, made of wood, however, did not last long. The second lighthouse was built in 1708, but it suffered the same fate as the first one. Smeaton undertook the third phase of construction of the Eddystone Lighthouse, which was a great help to sailors.
Many factors, including strong waves and salt water, affect adversely the construction of a lighthouse, so the materials used in the construction should be able to withstand them. Smeaton heated limestone to a high degree and pulverised it to produce a powder that was similar to today’s cement. This material, called hydraulic lime, was water-resistant and was ideal for the construction of the lighthouse.
The cement we see today was developed by an Englishman named Joseph Aspdin. He patented his invention in 1824 as Portland cement. Though many people had made cement in a similar ways over the years, Aspdin earned the reputation of being the inventor of modern cement after obtaining a patent. His cement was named Aspdin Portland Cement because its shape on solidifying was similar to that of Portland stones in England. Portland cement revolutionised the construction industry.
Portland cement, which was used only industrially in the early 19th century, began to be widely used in house construction from 1850s. The method of construction where iron frames were embedded in concrete was also developed during this period. A Frenchman named Joseph Monier is known for conducting experiments in this regard. In 1867, Monier patented this style of construction. The invention of steel and the possibility of reinforcing concrete with iron and steel led to new changes in the construction industry.
The Ingalls Building, a 16-story skyscraper built in 1902 in Cincinnati, Ohio, in the United States, was the tallest building built at the time. The purpose of the structure was to build trust among the people regarding the strength of concrete.
Renowned scientist Thomas Alva Edison was instrumental in promoting construction of concrete houses. Concrete houses built by Edison in 1908 can still be seen in the United States even today.
The environmental impact of producing and using concrete is a hot topic of discussion today. Many within the scientific community are suggesting a return to the Roman opus caementicium.
The invention of concrete mixing machines and ready-mix concrete accelerated the growth of the construction sector. Concrete was used in the construction of houses, roads, multi-storey buildings and dams. Today, any structure in the world – be it small or large – is made of concrete.
According to a report in The Guardian newspaper in 2019, concrete is responsible for 8 per cent of the world’s carbon emissions. It is also a testament to the extent to which concrete is used today. It is estimated that after water, concrete is the most widely used material by humans. That is the extent to which the world is dependent on this material.
The environmental impact of producing and using concrete is a hot topic of discussion today. Many within the scientific community are suggesting a return to the Roman opus caementicium. Roman constructions and Roman concrete were relatively environment-friendly because of the direct use of natural resources. Pozzolana, the main ingredient in the Roman concrete, is still available today, and researchers are working to make the right amount of Roman concrete in order to use it extensively in the construction industry, thereby reducing the level of pollution and building more sustainable structures.
Now put on your thinking hats and think about the following questions for a couple of minutes.
How do you describe the role played by Joseph Aspdin in the invention of cement?
Can you think of the ways in which the invention of concrete changed human lives?
Can you think of the reasons for scientific community suggesting a return to the Roman opus caementicium?
Write down your thoughts and discuss them with your students, children and your colleagues. Listen to their views and compare them with your own. As you listen to others, note how similar or different your views are to others’.
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