What are aggregates in concrete?

Aggregates have been used for years in construction for many different purposes, one of it’s main uses being used in concrete. Concrete can be used in many different ways, mainly being used for pavements, roads and grounding in general. Understanding the role of aggregates in concrete is essential to make sure that you are producing good quality materials for your construction projects. 

In this blog, we will discuss what are aggregates in concrete and delve deeper into their role overall. 
If you’re looking for construction aggregates, get in touch with SCB Grab Hire today.

What are aggregates?

There are many different types of aggregates, the majority of which are made from sand and stone, coming in either fine grade or coarse aggregate. Fine grade aggregates are thinner than coarse aggregates, identified as less than 4.75mm or being able to pass through a #4 sieve. On the other hand, coarse aggregates are always greater than 4.75 mm and are retained in a #4 sieve.

Benefits of using aggregate in construction?

  • Cost – Aggregate is often used as a filler within the concrete in order to cut down costs. It is vital to use cement in concrete but by using well-graded aggregates, good strength can be kept. You can get a strong ratio by using 60-80% aggregates for the volume of the concrete. The difference in price is noticeable, with cement costing 8 times the price of stone and sand. 
  • Strength
  • Elastic properties 
  • Thermal properties 
  • Volume stability
  • Dimensional stability 
  • Controlled shrinkage level
  • Cracking prevention

Why is it important to grade aggregate?

Well graded concrete, for example, fine aggregates tend to be better for concrete as they create a stronger finish. Aggregate is used in concrete to fill in the gaps. If you imagine that you have a bag of bowling balls, you could fill the space and make the content denser by adding golf balls, marbles and sand. This is why better-graded aggregates are used because they essentially have the ability to make concrete dense and of good quality.

Content ratios and shape

The shape must be considered when deciding what aggregates to purchase when making concrete. This is because certain rough-textured shapes will need more cement paste than round aggregates. Additionally, rough-textured aggregates will be more difficult to pump. This is why it’s so important to make sure that you choose the right aggregate. For concrete purposes, rounder shaped aggregates are better for concrete purposes. 

Sand is also an important factor when making up concrete. While stone creates a considerable amount of strength to the aggregate, sand offers the element of workability to the mix. It’s vital to make sure that you’re considering what your customer’s needs are when creating concrete. Depending on what the desired needs are, you may decide to oversand. Oversanding is used when pumping concrete to give it a better flow. You may also oversand if you wish to stamp the concrete for more fine detail. 

In summary, you should always first consider the purpose of the concrete, rather than the strength or cost.

Recycled concrete

Recycled concrete is made by removing, crushing and breaking concrete to a good size. Due to its raw look, it is mainly used as a base layer for other construction materials. 

Recycled aggregate can also be used for new concrete, but usually, the only portion used is coarse. You should keep the following factors in consideration when using recycled aggregate for concrete:

  • It will have higher absorption and lower specific gravity than natural aggregate.
  • Will produce concrete with higher drying shrinkage and creep.
  • The chloride content may be a concern if used in reinforced concrete.

Thank you for reading our blog ‘What are aggregates in concrete?’. If you’re looking for aggregates, get in touch with us at SCB grab hire today.

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