Concrete grain storage vessels, Buffalo, NY
It is nearly impossible to consider concrete as anything other than solid. Its very presence at any scale evokes a sense of permanence, which is obviously why we commonly refer to unchangeable things as concrete things. Unlike other common building materials such as wood, steel or glass, concrete seems to prevent change, alteration or replacement. It seems all we can do is add, and we certainly cannot move concrete things, at least not without considerable effort. The material is heavy of course, and hard, and seems to survive all but the salt of winter or the very shifting of the ground upon which it rests.
The solidity and permanence of concrete is ultimately the result of a chemical reaction between a combination of ingredients; it is a work of alchemy in that it pulls naturally occurring elements together, transforms them and produces a new result. As described by Sigfried Giedion:
“It is not extracted from nature as a compact material. Its meaning is: artificial composition. Its origin: the laboratory. From slender iron rods, cement, sand and gravel, from an ‘aggregate body,’ vast building complexes can suddenly crystallize into a single stone monolith…”(1)
The four base ingredients, as mentioned above, are cement, water, sand and aggregate in the form of small to large rock. A chemical reaction known as hydration takes place as water is added to cement. The curing cement holds the sand and aggregate together, and their varying sizes fill in the voids to ensure a solid section. The induced chemical reaction results in the crystallization of the cement, which ensures a tight grip between all parts.
1. Giedion, Sigfried. Building in France, Building in Iron, Building in Ferro-Concrete. Los Angeles: Getty Research Institute, 1995.
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