eli5 how does cement and concrete become hard if it’s only rocks and water
In: 12
A) It’s not just “rocks and water,” it’s some very specific kinds of rocks, refined in specific ways.
B) Terminology matters.
* **Aggregate** is the gravel and sand mixed in specific proportions with the cement and water to give it bulk and physical structure.
* **Cement** is the fine powder substance that acts as a binder for the aggregate.
* **Concrete** is the name for the end product of mixing aggregate, cement, and water.
Cement works because of specific chemical reactions that cause it to fill the spaces between the aggregate and then harden or “cure” in a way that holds everything together and (ideally) keeps out water/ice to prevent erosion. There are lots of different kinds of cement, but most commonly it’s limestone (Calcium carbonate) that’s heated to high temperatures to change its chemical composition so that in the future, when it’s mixed with water, it will react with carbon dioxide or similar to form a cohesive whole.
https://en.wikipedia.org/wiki/Cement#Chemistry
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