What is Aggregate? (Rocks, Sand, Gravel)

What is Aggregate? (Rocks, Sand, Gravel Explained)

Aggregate is the inert filler—rocks, sand, and gravel—that makes up 60-75% of concrete volume. While it's called "filler," aggregate actually provides most of concrete's strength. Understanding aggregate helps you understand how concrete works.

What is Aggregate?

Aggregate is the stone component of concrete:

• Rocks and gravel: Coarse aggregate (larger stones)
• Sand: Fine aggregate (small particles)
• Inert material: Doesn't react chemically (unlike cement)
• Volume: Makes up 60-75% of concrete volume

Types of Aggregate

Coarse Aggregate: Rocks and gravel (typically 3/4 inch to 1.5 inches)

Fine Aggregate: Sand (small particles that fill spaces between coarse aggregate)

Why Aggregate Matters

Aggregate provides concrete's strength:

• Structural strength: Rocks provide compressive strength
• Volume: Makes up most of concrete (more economical than cement)
• Durability: Hard rocks create durable concrete
• Strength: Concrete strength depends heavily on aggregate quality

How Aggregate Works

Cement paste binds aggregate together:

1. Cement paste: Cement and water create paste
2. Binds aggregate: Paste holds rocks and sand together
3. Creates composite: Together, they create strong material
4. Aggregate provides strength: Rocks carry the load

The Bottom Line

Aggregate is the inert filler (rocks, sand, gravel) that makes up 60-75% of concrete volume. Despite being called "filler," aggregate provides most of concrete's strength—the rocks and sand carry the structural loads. Cement paste binds aggregate together, but aggregate does the heavy lifting. Understanding aggregate helps you understand why concrete is strong and how mix designs work.

Need quality concrete? Contact Local Concrete Contractor. We use quality aggregate in our mixes to ensure strong, durable concrete for your project.