Structures built by in-situ construction or prefabrication coexisted for centuries: casting structural elements made of loose aggregates or bricks kept together by a binder, versus preparing large units made of stone, were ever alternative solutions. This means that both techniques ca be convenient and find respectively optimum application case by case, according to the performance requirements and ambient conditions. Since 3000 years ago and more, large stone units were cut at the quarry (and possibly finished on site) then assembled into the structure as columns, lintels, slabs, blocks, for public buildings (fig. 1) and city walls, as well as loose gravel or regular bricks were used with a binder for building masonry elements on site. By the end of 19th century, modern concrete appeared, as an artificial stone allowing for being shaped at will. Soon, portions of structures as walls, beams, slabs, poles, etc. were sometimes cast out of their final position, i.e., precast, then assembled and connected into the work. Noticeable were the applications promoted by great engineers: F. Coignet in France, with beams and wall panels, and G. Atterbury, in Britain, with wall panels for housing systems; later on, P.L. Nervi, in Italy, designed and built outstanding vault structures (fig. 2a). Such prefabrication was mainly made at the job site with crafts means, rarely in factories, and cannot be considered yet as properly industrial. Around 1930 E. Freyssinet devised the technique of prestressing concrete elements by tensioning high-strength reinforcing steel wires, which added them capacity and allowed for lighter structures, highly enhancing their performance. He also prefabricated members for his structures. On site prefabrication continued to develop, taking advantage of the new means. As an example, the domes of P.L. Nervi, built at the end of the 1950s for the Olympic games of Rome, reached with precast modular elements an architectural and structural value, impossible with traditional means (fig. 2b). However, only with the mid-20th century real modern industrial prefabrication broke out.
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