Precast concrete began with the ancient Romans and their refinement of pozzolanas, a natural cement, found in the soil.
Their mixtures of these cements, sand and gravels together made for the earliest invention of concrete. Their idea to pour this mixture into molds for building precast blocks marks the beginning of the idea for precast concrete.
The Roman armies were often kept busy with engineering projects, to prevent them from stirring up trouble at home. Concrete molds were filled locally by the tens of thousands at construction sites.
On the Roman aqueducts, there were hundreds of different forms; corner pieces, narrow, short or long blocks, etc. The individual blocks may have looked like quarried stone, but they were the first uses of precast concrete.