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An underground mithraeum in Ostia

History of cement: An underground mithraeum in the Roman port town of Ostia

History of cement

Cement is a very hard kind of rock that people make themselves. People all over Asia and North Africa used cement as a mortar to stick bricks together, or to make a hard floor, from the Stone Age onward, for instance in the Great Wall of China (about 200 BC).

Roman architecture
More about limestone
All our ancient Rome articles

What is cement made of?

But builders didn’t use cement by itself as a building material until the Roman Empire. You start with lime and powdered clay, and you add water.

Where does clay come from?

You mix it all up, and it turns into this soft squishy stuff, a lot like gray Playdough. Then you make it into whatever shape you want, or pour it into a mold, and let it dry. When it is dry it will be hard (like Playdoh) and even if you get it wet it won’t get soft again.

Is it cement or concrete?

If you want a stronger building material, you can add sand or gravel to your cement, and that makes concrete.

More about concrete

Cement in the Roman Empire

Architects in the Roman Empire used cement and concrete as a main building material beginning in the reign of Nero, about 60 AD, to build palaces like Nero’s Golden House, temples like the Pantheon, and shopping malls like Trajan’s Market. By using cement, builders could create huge domes and big open spaces with barrel vaults or groin vaults over them. Roman architects even figured out how to use special kinds of volcanic rock to make cement that would set under water, so you could use it to build ports for ships.

What is a barrel vault?
And a groin vault?
What is a dome?

Outside the Roman Empire, though, people did not use cement as a main building material. They went on using cement mainly as a mortar to stick stones or bricks together.

Cement in the Middle Ages

After the fall of Rome, about 500 AD, people didn’t build any big buildings in Europe or North Africa for several hundred years, and they stopped using cement or concrete except as mortar to hold bricks together. Medieval people got a lot of that mortar by burning Roman statues made of marble and limestone. They hated the statues because they weren’t Christian, so they were happy to burn them.

What is marble?
Metamorphic rocks
All our geology articles

Even in West Asia, Late Roman or Byzantine churches like Hagia Sophia, and early mosques like the Dome of the Rock, used cement only as a mortar. By the Middle Ages, people in Britain used coal fires to burn limestone to make cement. Medieval builders used cement mortar to build castles and cathedrals, but they didn’t use cement as a main construction material.

History of coal

Cement and steel – skyscrapers

Cement became much more important again when Besemer figured out how to make tons of steel cheaply in the 1850s.

Medieval and modern steel

With steel beams, you could build concrete-and-steel buildings that were cheaper than stone or wooden buildings and could be much taller.

Learn by Doing: Cement

Cement to concrete

Bibliography and further reading about the history of cement:

Cement to concrete
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