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Why Are Aggregates Used in Concrete?

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    Posted on 21st December 2017 by Hintons

    As one of the main ingredients in concrete, the aggregates you use will influence the overall properties of the mix – from consistency and workability to strength and durability. But exactly why are aggregates used in concrete?

    The size, shape and amount of aggregates used in a mix are all important factors to consider, and in this article we’ll look at the effect aggregates can have on concrete.

    Not just filler

    Going by volume, aggregates make up roughly 60-80% of a typical concrete mix, and is often seen as a filler material – there to give the mix more substance but not much else. However, aggregates are far more than mere filler.

    Something as simple as the size, shape and texture of your aggregates will influence your mix. You’ll usually have a choice between using finer, smoother aggregates – such as sand or natural gravel – and more angular and rough aggregates such as crushed stone.

    Finer, smoother aggregates generally produce better workability of the mix, while rougher and larger aggregates are good for higher strength mixes – but may prove more difficult to work with.


    Workability of concrete mix refers to how easy it is to mix, transport, lay and compact. A mix with high workability means it is easy to work with – it can be poured and mixed without difficulty. Workability is directly influenced by the amount and type of aggregates chosen.

    Workability increases with smaller, finer and rounded aggregates, but uniformity is also important. If your aggregates are consistent in size, more cement is needed to bond the aggregates together because there is greater space between the aggregates. For mixes using aggregates of varying sizes, spaces are more easily filled – reducing the amount of cement paste required.

    Not only does this impact workability, it also directly affects strength and overall cost. The more space to fill, the more cement required and the less workable the concrete. Cement is the most expensive part of the mix, so the more cement needed, the higher the price of the mix.

    The relationship between the ingredients of a concrete mix is interdependent, so aggregates need to be selected carefully to attain the mix you desire for your project.

    Finding the right balance

    While reducing the cost of concrete sounds appealing, the right balance needs to be met otherwise the mix will not match your requirements. Overloading a mix with aggregates will make it cheaper, but it will also make it significantly harder to work with. The cement paste won’t bind the aggregates together and this weakens the mix.

    For an ideal balance, you need to choose the right proportion of aggregates to minimise the amount of cement required, while preserving the necessary strength for your project. The proportion of ingredients depends on the type of aggregates you’re using, their size, shape and texture as well as their natural moisture content. Your concrete provider will happily advise you on all of these factors.

    Aggregates are important

    Thinking of aggregates as filler material will sabotage your concrete mix. If you’re looking for concrete for a building project – whether it’s a driveway, patio, shed foundations or something more substantial – your choice of aggregates will affect your concrete from initial mixing to the final pour and compaction.

    Most importantly, your aggregates need to be of a high quality. Aggregates should come quality assured, ensuring that they meet the requirements necessary for use in construction concrete mixes. This goes for recycled aggregates as well as raw mined aggregates, such as gravel, sandstone and crushed stone.

    When selecting aggregates for your project, you should only use reliable and reputable suppliers. At Hinton’s Grabs and Skip Hire, we only supply quality aggregates that are processed at our concrete plant, mixed precisely to meet your project demands.

    For a prompt supply of construction aggregates in London and Croydon, look no further than Hintons Waste. We can deliver your aggregates to your worksite or you can collect aggregates directly from us. Whatever your requirements, we can help you find the ideal selection of aggregates for your concrete mix, so to enquire about our aggregates and hardcore services, simply contact us today.


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