Although we think of concrete as a modern building material, it was invented by the Egyptians, who used a primitive form to make bricks, around 5,000 years ago. The Romans developed the material further and used it extensively. They made concrete from a mixture of lime, volcanic ash and used animal products like blood, fat and milk as binding agents.
The best-known example of a Roman building made from concrete is the circular, domed Pantheon in Rome, which was built around the year 200 AD. After the fall of the Roman Empire in 400 AD, concrete was forgotten about for centuries.
What’s in it?
Modern-day concrete, by volume, is usually 60-75% aggregate (a mixture of sand and gravel), 15-20% water, 10-15% cement and 5-8% air. It’s an easy material to make, as the aggregate and water are widely available. Only the cement needs to be transported, but this ingredient isn’t needed in large quantities. Concrete is very versatile and can be shaped in many ways by pouring it into a cast and leaving it to harden.
How useful is it?
Concrete is used everywhere. We see it being used for retaining walls, bridges, building foundations, piers, basement walls and in arches. Architects are using concrete more frequently these days as it’s quite a green building material and can be used decoratively as well as structurally. The fact that concrete can set even when underwater makes it invaluable for use in dams and the submerged parts of bridges.
Concrete is used almost as much as water
Around 10 billion tonnes of concrete are made and used every year around the world. Worldwide, the concrete industry is worth more than £23.5 billion, and more than 70% of people in the world live in a dwelling structure that uses concrete. The good news for these people is that concrete gets stronger as it gets older.
Concrete is surprisingly environmentally friendly
We’re used to thinking of concrete as the main player in the modern-day, dystopian urban jungle, but it’s actually very good for the planet in many ways. The colour of concrete means that it reflects up to 50% more light than tarmac or asphalt, which can reduce the temperatures in big cities by as much as 7%.
It’s also the best material to have around in a disaster as it withstands floodwater, drought and minor earthquakes, especially if reinforced by steel rods. During the First World War there was a shortage of the steel usually used to make ship hulls, so a Norwegian innovation saw ships, tug boats and barges made from concrete! Concrete can float because, in some mixtures, the buoyancy is greater than the weight of the material.