From ancient times to Mars and beyond. This is the fascinating history of concrete and our exploration of the future.
Concrete can be a little controversial - it is a power and water guzzling process, but as you’ll see below there are opportunities to be creative and sustainable with this very necessary construction material.
Although concrete and cement are sometimes used interchangeably, cement is actually an ingredient in concrete. It was developed by the Ancient Romans, by mixing lime, water and volcanic ash.
Cement is the powder form which you would add water to to create a paste. When the a rougher aggregate like gravel or sand is added, that is when you have concrete.
"Concrete is made when you add water and a rough aggregate to the cement."
The largest concrete structure in the world is Three Gorges Dam. Built in 2003, it stands at 607 ft tall and 7,575 ft long! You can find it crossing the Yangtze River in China.
2 billion tonnes of cement are produced every year and as an ingredient in concrete it is the most used man made construction material in the world.
But how did we get here?
At its origins, what we understand by concrete and cement, can be traced back to Ancient Rome. Crushed limestone mixed with sand and water created our early cement - the dry mix without the rough aggregates mentioned earlier. Historians and US scientists have explored Roman cement around the Pozzuoli Bay, near to where Pliny the Elder a 1st century Roman scholar lived, and they have discovered the secret of the durability of Roman cement.
"Crushed limestone mixed with sand and water created our early mortar."
Pliny the Elder wrote about the use of volcanic ash in cement but as historians and scientists have discovered is it was smarter than that.
Roman’s mixed lime and volcanic ash to create cement. Then they would mix sea water with them which triggered a chemical reaction. The water would hydrate the lime which then reacted with the ash cement. All of this mixed together created a calcium-aluminum-silicate-hydrate, or C-A-S-H, bond. This bond was incredibly strong.
China also has a rich history attributed to its construction materials and methods.
For instance, the Great Wall of China is one of the most impressive structures in the world. It has truly passed the test of time. But, how did they do this? The strength of the mortar can be attributed to sticky rice.
"The strength of the mortar used on the Great Wall of China can be attributed to sticky rice."
By combining a sticky rice soup with slaked lime they created a type of mortar that was far stronger than any other of its time. What gave the mortar its strength was amylopectin, a form of complex carbohydrate found in rice and starchy foods.
It was one of the most innovative advances of its time.
From the 1700s we can see a more direct path to the type of concrete we use today.
John Smeaton, an 18th century engineer, was tasked with building a lighthouse and he needed a quick drying cement. It was during this time that he developed hydraulic mortar. It’s a quick drying cement that stops water and leaks. The hydraulicity is directly related to the levels of clay in the limestone used.
"Hydraulicity in concrete is directly related to the levels of clay in the limestone."
It’s perhaps the first contemporary indicator of the cement we work with today.
It is the 19th century invention of Portland cement that brings us to now.
Inventor John Aspdin, invented his own version of Smeaton’s cement by burning up ground chalk and crushed clay in a lime kiln. They were burned until the carbon dioxide evaporated leaving behind a strong cement.
"Aspdin's version was developed by burning ground chalk and crushed clay in a lime kiln until the carbon dioxide evaporated leaving behind a strong cement."
Aspdin and Smeaton’s developments have led us to the concrete we use today, but what’s next for the world’s most used construction material?
Bioactive concrete is a type of dense and porous concrete with damp ledges to create a perfect environment for plant life to grow and flourish. Much like living walls, bioactive concrete has multiple positive uses including air purification, insulation and emotional benefits known as biophilia. Biophilia is the theory that we as humans benefit from being around nature and plant life.
Then there’s light emitting concrete. It absorbs and radiates natural or artificial light creating this beautiful glow in the dark effect. The brainchild of Dr Jose Carlos Rubio Avalos of the UMSNH of Morelia, it is a response to the need for more dynamic construction materials. In a world where we are working hard to find more creative and eco friendly ways to sustain our lifestyles this could be one of the answers we are looking for.
Lin Wan and colleagues at Northwestern University in the US have come up with martian concrete. That’s right! We are getting ever closer to our future in space. The key ingredient would be sulphur. This sulphur would then be heated up to 240 degrees celsius until it formed a liquid. Then we mix martian soil, which would act as an aggregate, with the liquid sulphur. As the liquid solidifies it binds the aggregate making concrete!
With a rich history and an exciting future, concrete is an incredible construction material.