I recently visited a factory that makes prefabricated concrete parts. I was astounded by the amount of handwork and artistry is involved in making the pieces, just as I was at the plywood factory . It turns out that brick - which has the connotation of being close to the hand and human scale - is in fact the construction piece that can be fabricated with the least human contact. (see here ) Concrete, the actual substance of cement mixed with aggregate, is the least of the ingredients. Prefabricated concrete parts are actually made of a lot of carpentry and a lot of metalwork. The density of metal was impressive. Each rod has to be bent to the right shape and tied into place with wire. The bending of the metal is done mostly by machine, especially for the repetitive pieces. But the wiring is done by hand. I watched a worker deftly twist many pieces using a kind of large crochet hook. Reinforced concrete is probably the construction technique that has had the most impact on