Roman concrete

Opus caementicium ( in German usually Opus caementitium written except in archaeological reference books, also known as cast masonry) is the Latin term for a concrete- like substance, with which the Romans proved to be more than 2000 years ago, building foundations fastened. In particular, water pipes and piers were lined with the opus caementitium to achieve a certain resistance to water. Large parts of the Colosseum in Rome consist of opus caementitium, but also the Roman domed buildings with huge spans (eg the Pantheon in Rome: dome 43 meters in diameter) were made ​​possible by the use of opus caementitium. It is a precursor of today's concrete.

Opus caementitium was mixed of stone, sand and calcined limestone, were being buried as a supplement pozzolans. Only through the incorporation of pozzolans received the opus caementitium those hydraulic properties, whereby said mixture cured by the addition of water to a pressure-resistant stone - similar to our current concrete. Opus caementitium therefore cures even under water. By adding water to the burnt lime reacted under intense heat and the resulting opus caementitium was hot or cold formed and processed, the lime ingredients were highly corrosive and could result in contact with the eyes to blindness.

The opus caementitium made ​​man independent of the form of boulders and the painstaking carving of stone, for the first time the molds were poured. In this case, the space of an outer and inner, clean brick with cut stone bowl was filled with opus caementitium. This cast masonry / cavity masonry called opus implectum. Frequently were inserted as compensation layers and improve the stability of the shells regular layers of bricks (bricks leading).

Also the Phoenicians ( > 1300 BC ) mixed their mortars with pozzolans to reach the solidification under water.

In the Middle Ages it was from partly from the use of opus caementitium because the knowledge had been lost by the effect of pozzolans or they were not available. Nevertheless, locally degraded Trass was often used as an aggregate.