The Romans might have made it better, but right now cement is one of the world’s most used materials, period.
Concrete is one of those technologies that was used for centuries—in this case, by the Romans—and then had to be invented again centuries later. But once we rediscovered it, we were hooked. The only thing that humans consume more of, by volume, than water is cement, concrete’s key ingredient. We use so much of the stuff that the cement industry is responsible, all on its own, for 5 percent of global carbon dioxide emissions.
The idea is simple enough: you mix together small particles (like sand) and slightly bigger particles (like tiny pebbles) with water and some sort of paste that will set and keep the whole thing together. (It’s this last bit that’s the tricky part.) The Romans made concrete of lime and volcanic rock, and they had some pretty good ideas about what it should be used for:
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