Concrete is one of those things that would be difficult to live without in modern society. It is inexpensive, easily shaped and rock solid once it cures. We use it for roads, bridges, sidewalks, building foundations, skyscrapers, dams, pipes, subway tunnels, runways, parking decks… The list is long.
Concrete is made from cement, sand, gravel and water. But where does the cement come from? Here’s the answer:
You start with limestone from a limestone quarry. It is crushed and heated in a rotary kiln to remove carbon dioxide and fuse the materials to form clinker. The clinker is ground into a fine powder. This is cement.
[[[Jump to previous question - what is Google Wave?]]]