What is Volcanic ash (pozzolana)?

Volcanic ash, also known as pozzolana, is like a special kind of sand that comes from volcanoes.

Imagine you're playing in the sandbox at the park. Normally, the sand is just plain old sand, it’s good for building castles, but not much more. Now imagine if this sand had superpowers: when mixed with water and another type of powder called lime, it could become as strong as bricks or concrete!

That’s what volcanic ash does. It comes from tiny bits of rock that are shot out of a volcano during an eruption, like how you throw tiny pebbles into the air when you're playing at the beach.

When volcanic ash mixes with lime and water, something interesting happens, they stick together really well, creating a super-strong material. This is used to make concrete that lasts for hundreds of years!

People have been using this special sand for thousands of years, even in ancient Rome! They called it pozzolana, after the town of Pozzuoli near Mount Vesuvius, one of the most famous volcanoes in the world.