How Are Aggregates Used in Concrete?

As you already know, there are a plethora of ways to use aggregate rocks for residential, commercial, and industrial purposes. They do everything from protecting bridges and coastlines to providing aesthetic enhancements around home gardens.

What about poured concrete? How do aggregate rocks fit into the mix?

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How Are Aggregates Used in Concrete?

Aggregate materials may comprise as much as 80% of concrete mixtures. That may surprise some folks, but it’s a testament to the effectiveness of various rock materials.

What are aggregates?

These are granular substances that support concrete by holding the mix together to achieve its solid form. It can be as fine as sand or as coarse as gravel or stone. At any rate, there’s a lot you can do with the right balance of cement, aggregates, and water.

Here’s a quick reference for how to mix those materials at appropriate rates.

Typical Mix Proportions

  • Aggregates – Between 60 to 80%
  • Cement – Between 7 to 15%
  • Water – Between 14 to 18%
  • Air – Between 2 to 8%

Critical Mixing Issues (Why You Need a Pro to Do This)

  1. Quality Aggregates – Although aggregates are terrific for use along with concrete, you still have to select the right kind. The best-quality aggregates contain clean and durable particles, free of other chemicals, clay coatings, or any other foreign contaminants. Perhaps for obvious reasons, you don’t want the soft/porous kind for cement mixing.
  2. Moisture Levels – All concrete mixing requires plenty of attention to moisture levels. Aggregates absorb water, so a concrete professional would need to account for the way it affects the water-concrete ratio. 
  3. Coarse or Fine Aggregates – You can use either coarse or fine aggregates or some combination of both. For finer rocks, select those that fit a fineness modulus (FM) between 2.3 and 3.1. Anything too fine will require too much water for the mixture. As for coarse aggregates, the sizing depends more on their shape, reinforcement, and proximity to reinforcement materials. They shouldn’t be too close to the steel rebar, and cannot go beyond one-third the depth of the concrete slab.

Other Mixing Factors

Whether you use aggregates for the task, all the other rules for pouring and mixing concrete still apply. The typical curing time for cement mixtures is about 28 days.

However, especially in our neck of the woods (Florida), you have to factor in the outdoor temperature and ambient humidity. Therefore, it’s not a DIY-friendly type of job.

We hope you enjoyed this and learned more about how to integrate aggregate materials into concrete mixtures. You can learn all about aggregate materials, like Rip Rap, by partnering with the dedicated professionals at Delta Aggregate. We’ve used almost every rock imaginable for various jobs (big or small) at some point or another.

Find out more about our service by calling our Immokalee location at 815-791-8377.