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Aggregates Explained

In order to learn more about concrete and its properties, we must first take a look at aggregates to understand the role it plays in giving concrete it’s all-too familiar characteristics and properties, making it such a reliable material to work with.

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What are aggregates?

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Aggregates are rock or mineral fragments that come in all shapes and sizes. As a purely natural material, aggregates are differentiated by grades, such as 1-3mm, 2-5mm etc. that are all suitable for different uses – we’ll discuss this further later on in the article.

Classified as either normal weight, lightweight or heavyweight, they are either a coarse or fine consistency and undergo a process of: washing, drying, screening, grading and bagging, prior to use.

What are aggregates made from?

They originate from bed rocks and can vary largely in structure and texture. Aggregates are a mass of fragments or particles that can be compacted together and are widely used as a reliable construction material. Around 80% of aggregates are derived from sedimentary rocks, for instance sandstone, and some from metamorphic rocks, such as gneiss.

What are aggregates used for?  

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Aggregates can be, and are, used for a whole range of purposes. This can either be for construction purposes, such as laying a sub-base or for decorative purposes, such as landscaping.

When mixed with water and cement, aggregates are a vital ingredient for concrete. Not only do aggregates give body to the concrete itself, but they also helps reduce shrinkage and occupy as much as 70-80% of the concrete mix.

In terms of concrete, the size of the aggregate particle is rather important and can affect the following things: water demand, concrete content and microcracking.

Aside from concrete, aggregates are commonly used for driveways, pathways, patios and borders, to name a few.

Examples of aggregates

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There are a range of different aggregates available for different uses. Here is a list of the aggregates we stock at Neil Sullivan & Sons, and a brief description of what they are commonly used for:

Gravel and Stone Smooth, round stones with a nice appearance are ideal for patios and pathways. Gravel is often used for road constructions and foundations.

Building Stone  Mainly used for construction purposes, such as building walls and sometimes roads too. Alternatively, when crushed, the stone can be used to make concrete.

Ballast – Mixed with cement and water to create concrete that can be used for things such as sub-bases e.g. shed bases.

Slate Chippings These are mainly used for decorative purposes, such as a replacement for lawns in gardens. As the formation of the particles are angular, and therefore able to withstand heavy weight, slate chippings can also be used for driveways.

Pea Gravel – Largely used for aesthetic purposes e.g. landscaping and walkways.

To find out more about our range of different aggregates, or for advice on which type is most suitable for your requirements, please don’t hesitate to get in touch with the team at Neil Sullivan & Sons.


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