Cement vs. Concrete

Cement is the base aggregate. It’s limestone, silica, and some other things. It’s a very fine powder.

Cement, when mixed with other things, makes concrete. You mix it with sand, rocks, and water.

So, the sidewalk in front of your house is technically concrete, not cement. Cement is just one ingredient in it.

From a page from MIT entitled Explained: Cement vs. Concrete – Their Differences, and Opportunities for Sustainability:

“Cement is then brought to sites where it is mixed with water, where it becomes cement paste,” explains Professor Franz-Josef Ulm, faculty director of the MIT Concrete Sustainability Hub (CSHub). “If you add sand to that paste it becomes mortar. And if you add to the mortar large aggregates – stones of a diameter of up to an inch – it becomes concrete.”

From another page at the Concrete Contractors Association entitled Whats the Difference Between Cement and Concrete?

Concrete is basically a mixture of aggregates and paste. The aggregates are sand and gravel or crushed stone; the paste is water and portland cement.

“Portland cement” is the most common type of cement, named for a type of stone from the Isle of Portland, in England.

Why I Looked It Up

I built a house in the Domincan Republic in the summer of 2022. To pour the concrete base, I spent two hours mixing the following:

• Bucket of cement
• Bucket of water
• Bucket of sand
• Bucket of rocks (kind of a gravel mixture)
• Bucket of sand
• Bucket of rocks
• Bucket of sand
• Bucket of rocks

So, eight buckets went into every load. Only one of which was about a half-full of cement, which was a very fine powder (and the lightest of the three buckets to lift).