It’s hard to put an exact time period on when concrete was the first invented as it depends on what you consider ‘concrete’. Ancient materials which are similar were made using gypsum or limestone. When sand and water are added to these, they become mortar, a plaster-like material used to glue stones together. Over many years, this mix has been improved upon, morphing into modern concrete.
The first ‘concrete’ was created at around 1300 BC when Middle Eastern builders realised that coating the outside of their fortresses with a thin, damp layer of burned limestone, it reacted with the air to form a hard surface. This wasn’t by any means concrete, but it was the very beginnings of cement.
Early cement-like materials included mortar-crushed, burned limestone with sand and water. This was used for building with a stone instead of casting in a mold – which is the contemporary way of using concrete.
As one of the main components in concrete, cement has been around for some time. Around 12 million years ago in the area we now call Israel, natural deposits were created due to reactions between limestone and oil shale from spontaneous combustion. But – cement is not concrete, it is just one part of it.
The Early Use of Concrete
The first concrete-like structures were built by the Bedouins or Nabataea traders who occupied regions of Syria and Jordan in around 6500 BC. They later found the advantageous use of hydraulic lime (cement which hardens underwater). By 700 BC they were supplying mortar to construct rubble houses with concrete floors and underground waterproof cisterns. These cisterns were a secret and huge part of how they stayed alive in the desert.
By 600 BC the Greeks found a material which developed hydraulic properties when combined with lime. This was no match to the Romans, however, who were very successful with their early concrete. This was not flowing, but more of a cemented rubble.
In around 300 BC the Egyptians used a mud and straw mix to create bricks. When building the pyramids they also used gypsum and lime mortars. At around the same time, the northern Chinese used their own form of cement in building the great wall. Testing has shown that the main ingredient on the mortar used for this was a glutinous and sticky rice.
Read about some impressive concrete structures here.
Concrete today is created using Portland cement, a mixture of fine and coarse aggregates of sand, stone and water. Chemicals are also added to control how it sets, but these are mainly used in construction in environmental extremes.
Concrete can be modified according to the different settings and forces it will need to resist. The ingredients of concrete and the proportions of the ingredients used is referred to as ‘the design mix’.