- Concrete is a construction material that consists of “aggregate” (crushed stone, sand etc.) which is bonded together with a paste (cement).
- Modern cement is made by heating calcium carbonate (limestone) which then forms calcium oxide (quicklime). Other substances are then added to it and the resulting product consists of calcium silicates.
- Unreinforced concrete has low ductility meaning it is prone to deformation and so it cracks easily. This problem is solved by setting concrete around reinforcing bars (rebars) thereby creating reinforced concrete.
- Reinforced concrete was invented by the French industrialist François Coignet in 1852.
- Unreinforced and reinforced concrete look the same from the outside. But they’re different on the inside.
Here is a photograph of François Coignet: