Alkali-aggregate reaction

Alright kiddo, so you know how we use concrete to build things like roads, bridges, and buildings? Well, sometimes the materials that are used to make the concrete can have a little reaction that creates some problems.

When we make concrete, we mix different things together like sand, gravel, and cement. Sometimes, there can be a problem when we use certain types of rocks in the mix. These rocks are called aggregates, and the problem happens when they react with something called alkali.

Alkali is a chemical that's in things like cement and water. When it comes in contact with certain types of aggregates, like some types of rocks, it can cause a reaction. This reaction causes the concrete to expand and crack over time, which can be dangerous.

This problem is called alkali-aggregate reaction, and it can happen in different ways. Sometimes it happens quickly, and other times it can take years to show up. Engineers and scientists have to be very careful when they're making concrete and using certain types of aggregates so that they don't cause this reaction.

So, that's the basic idea of alkali-aggregate reaction. It's when certain types of rocks in concrete can cause a reaction with chemicals in the mix, which can make the concrete crack and become unsafe over time.