Materials used in the construction of the Colosseum were chosen carefully. In the below of the building, heavier materials such as tuff and lime were used, which was known as grading.
Roman builders know and discovered different techniques to build this giant edifice. Stronger but lighter mortar, bricks and volcanic stone were used by them.
The Materials used in Colosseum:
- 1 – Travertine: The limestone which was used in the main pillars and walls were strong and brought from Tibur. It was generally white or yellow.
- 2 – Tuff: Tuff is softer than travertine and it brings elasticity. However; since it was not resistant to the fire, the damage was bigger in cases of big fires in Colosseum.
- 3- Concrete: Concrete was invented by the Romans. It was cheap, quick to make, and easy to use. To make concrete, the Romans dropped pieces of rubble into sticky mortar made of lime (a powder of burned chalk or limestone), water, and pozzolana (a volcanic ash). The mortar hardened as it dried, holding the concrete together. Rubble gives concrete its strength. Big lumps of heavy rubble were used in the Colosseum’s foundations. Small lumps of light rubble were used in the upper walls.
- 4- Bricks: Bricks were mixed with water, sand and tiles.
- 5 – Iron / Bronze Clamps: In order to bind stones together these clamps were used.
- 6 – Marble: Marble is used both in decoration and the entrances of the cavea in Colosseum. Some of the columns are also made of marble. The first three marble rows were for the nobles and special guests.
- 7 – Lime: Lime was used as binder for the cement by adding water. It was made of limestone which is heated.
- 8 – Mortar: Mortar is mixture of cement/sand and water. There were two types of mortar: The first one is lime mortar – the one we mentioned above, and pozzolanic mortar – the volcanic ash which is an aluminous material reacted with calcium hydroxide.
- 9 – Stone: Stone was used on the outside walls of Colosseum and the sections of the building that took the most weight. Big lifting cranes hoisted stone blocks into the air. They were powered by roman slaves walking around and around a treadwheel. Inside walls of Colosseum and underground passages (called Hypogeum) were built using heavy concrete and brick. The upper levels were built with less heavy materials, such as wood, bricks, and the lightest concrete.