Concrete

Concrete is an important material for making different buildings and structures. It is a composite made of Portland cement, sand, gravel or aggregate, and water in varying proportions depending on the task.

Concrete is used more than any other man-made material in the world.^[2] As of 2006, about 7.5 billion cubic meters of concrete are made each year—more than one cubic meter for every person on Earth.^[3]

The ingredients are mixed together into a paste, a bit like making dough for bread. The concrete is then poured into a frame. After a few hours it sets hard. Concrete solidifies due to a chemical reaction known as hydration. The water reacts with the cement, which bonds the other components together, eventually creating a strong stone-like material.

link source : https://simple.wikipedia.org/wiki/Concrete