MUNDANE MYSTERIES: Cement Vs. Concrete

We walk on sidewalks all the time, so much so that we usually don’t ever think about the stuff we’re stepping on: the rigid, smooth, gray hard stuff under our feet. But, have you ever stopped to wonder what the proper name for that stuff is? Is it concrete, or is it cement? And, what’s the difference between the two?

Well, while they’re often interchangeable, concrete & cement actually describe different yet related elements of the blocks, flooring, and walls that comprise so many common structures. Basically, concrete is the gray, gritty building material used in construction, while cement is an ingredient used in concrete.

Cement’s a mixture of dry powder that looks very different from the wet sludge poured out of cement trucks. Cement is made from minerals that have been crushed up & blended together. Just what minerals cement’s made from can vary: clay and limestone are regularly used nowadays, but anything from seashells to volcanic ash also works. Once the ingredients are mixed together the first time, though, they’re fired in a kiln at 2642°F, forming strong new compounds, before being cooled, crushed, and combined again.

That mixture alone is useless, though. Before it can be used in various construction projects, the cement has to be mixed with water & what’s called an “aggregate”, like sand, so that it forms a moldable paste. THAT substance is known as concrete. It fills whatever mold it’s poured into & hardens fast into a solid, stone-like form. And that’s, in part, why it’s the most widely-used building material on the planet.

So, whether you’re drawing your initials into a wet slab of sidewalk, power-hosing your patio, or maybe admiring Brutalist architecture, that’s concrete you’re involved with. But, if you’re ever handling some chalky gray powder that hasn’t been mixed with water, that’s what you call cement.

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