Compressive strength Facts for Kids

Measuring the compressive strength of a steel drum

Compressive strength is how much a material can be squeezed or pushed before it breaks. When a material reaches its limit of compressive strength, it gets crushed. For example, concrete can be very strong when pushed. Many concrete buildings can handle pushing forces greater than 50 MPa (megapascals). But a soft rock like sandstone might only handle 5 or 10 MPa before it breaks.

What is Compression?
- Atoms and Forces
Measuring Compressive Strength
- How the Test Works
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What is Compression?

When you pull on something and it stretches, we say it is under tension. Think of pulling a rubber band. But if you push on something and it gets shorter, it is under compression. Imagine squeezing a sponge.

Atoms and Forces

Inside any solid material, there are tiny particles called atoms. When a material is under tension, these atoms are pulled slightly apart. When it is under compression, the atoms are pushed closer together.

Atoms in solids usually try to stay at a certain distance from each other. So, when they are pulled apart or pushed together, forces appear inside the material. These forces try to bring the atoms back to their normal positions. This is why materials resist both pulling (tension) and pushing (compression).

Measuring Compressive Strength

To find out a material's compressive strength, scientists do a compression test. They use a special machine, similar to one used for pulling tests. But instead of pulling, this machine pushes on the material.

How the Test Works

Usually, a small piece of the material, often shaped like a cylinder, is placed in the machine. The machine then slowly pushes down on the cylinder. As it pushes, the cylinder gets shorter and wider. The machine measures how much force is applied and how much the material changes shape.

The compressive strength is the highest pushing force the material can handle before it completely breaks or crushes. This test helps engineers choose the right materials for buildings, bridges, and other structures that need to withstand heavy loads.