What's the Difference Between Cement and Concrete?

We get asked this question sometimes. A lot of people use the terms concrete and cement interchangeably. But they are not the same thing. In fact, cement is an ingredient of concrete.

The earlier known forms of cement were made with limestone and ash, back as long ago as 12,000 years. The Gobekli temple site in Turkey is at least that many years old, and excavations have found that the builders were using a form of cement as a mortar and joiner.

Our ancestors discovered that they could make cement by using a mix of crushed limestone, fire ashes or volcanic ash, clay, and iron. Lots of different types of material can go into cement, but limestone is a key ingredient because of the high calcium content. Many different forms of cement exist.

In 1824 Portland cement was invented. This is the most commonly used modern form of cement, and it is produced through extremely high heat which breaks down limestone, shale, sand, and iron ore into a fine powdery cement.

To make concrete, Portland cement is mixed with sand or gravel, and water. It’s the water that is key to the concrete process, as instead of simply hydrating the mix, it sets off a chemical reaction that cures it. As the concrete cures, it hardens. It can take days or even months before the curing process is complete and the concrete is at full strength. The chemical reaction that cures concrete actually gets quite hot in the process.

If only sand is added to the cement and water, congratulations, you have made mortar or a form of grout. Concrete is made when sand, gravel, cement, and water are mixed together. Some new forms of concrete mix in lighter perlite or vermiculite to make a lightweight and insulating concrete. Other additives can create other specialized properties as well.

Not all concrete is equal. The Romans used a form of concrete that included volcanic ashes and tuff (volcanic rock). Some of their buildings, like the Pantheon and the Colosseum are still standing. We still to this day cannot recreate their recipe for concrete. You may notice that some modern concrete structures are already cracking and breaking down. It turns out we are still figuring out the best ways to produce cement and mix concrete.

The simplest way to explain the difference between concrete and cement is to say that cement is an ingredient in concrete. And it’s true. But given the variety of ways to make cement, and the variety of ways to mix concrete, the real answer is a little more complex.