From humble soil to trendy slate chippings, aggregates can be found EVERYWHERE! The dictionary definition of aggregates is granular materials that don’t stick or clump together, sounds pretty boring, right? Well, these materials are the foundation of much of our modern world and play a more important role than you might realise. In this guide, we’ll look at some different types of aggregates and show you how they’re made.

Aggregates Stoke-on-Trent — *Some piles of chrushed material*

A material world.

Whilst you might think of construction or landscaping when you hear the term aggregates, the reality is that almost all products are made using aggregates as their base material.

Choosing the right aggregate is important as each one has different qualities that make it suitable for different applications. These qualities may include strength, texture, shape, colour, and resistance to wear.

Most aggregates you’d use today are made from a group of minerals commonly referred to as feldspar, which make up the majority of the earth’s crust. These minerals are used in everything from ceramics to paint. Let’s take a look at some of the better-known minerals that make up feldspar.

Granite, which is originally made from quartz and other minerals is widely used in construction due to its strength and toughness. You’ll find this in roads, concrete, and drainage systems.

Gypsum, which is mainly made up of sulphur and calcium has many uses, you’ll find this commonly used in plaster and cement, but also in toothpaste and shampoo!

Dolomite is made up mainly of calcium and magnesium and is used as a base material to create magnesia which is commonly used to produce glass, ceramics, and even bricks.

All aggregates must be collected from the earth in their raw form and processed into usable materials, now that you’ve seen where the materials come from, lets take a look at how they are processed and manufactured.

Aggregate production.

The first step in our process is to extract the base material from Mother Earth, Mother Earth doesn’t want us to have any of her precious minerals, so we have to use drastic measures such as explosives and heavy diggers to wrench them from her grasp. This process is commonly referred to as “mining” or “quarrying” (a quarry is basically an open top mine i.e. it isn’t down a tunnel or mineshaft).

Once the rock has been broken up with explosives or machinery its transported away from the area (which is commonly called the “face”), by trucks or large conveyors into a processing area. Most quarries will have what is called a “primary crusher”, this is a machine which smashes the large pieces of rock into smaller, more manageable, chunks.

After primary crushing, the material then goes through a process known as “screening”, if you’ve ever tried your hand at baking, you will probably have used a sieve. Screening is a similar process where the material is separated out depending on its size.

This process of crushing and screening is repeated until the rock is separated out to the required size, in the case of gravel, the usable material can be made in stages depending on the size of pebble the customer requires, whether that is 20mm, 40mm, etc. The material will probably be transported away from the quarries to specialist screening companies using large boats or trains to complete this process.

Size matters

As you can see aggregates are essentially mined material that is broken down and then mixed together to create a usable material. As materials are crushed and screened, they can be separated into different types, depending on where they are in the process.

If we look at construction aggregates there are 3 main types of aggregates used, these are natural, secondary, and recycled.

Natural or primary aggregates are materials that have had minimal processing, these can include crushed rock, gravel, and sand.

Secondary aggregates are generally made by combining industrial waste materials such as slag and other by-products with virgin materials such as china clay to create a new aggregate.

Recycled aggregates are made by reworking old construction materials such as concrete, tarmac, and glass.

Different types of construction aggregates

Out of all the industries you’ll find that construction uses the most aggregates. Up to 80% of concrete is made up of aggregates, when you think of a building estate or housing block that’s a lot of aggregates! The six most common aggregates you’ll find used in construction are MOT Type 1, gravel, top soil, ballast, sand, and crushed concrete.

MOT Type 1- You’ll find this aggregate used as a base material for driveways, roads, playgrounds and everything in between! Proper Type 1 is certified as having the correct properties for this use and is made from crushed rubble and concrete. You’ll find a mixture of different sized pieces of material from 40mm down to dust. This material compacts well and is very strong once compacted.

Gravel- You’ve seen gravel used everywhere from driveways to soakaways, this aggregate is a naturally formed material that is generally sorted into pieces of the same size. You can also make gravel by crushing larger rocks. It’s a tough, hard-wearing material with excellent drainage properties.

Top soil- Good old dirt! This is another primary aggregate that is generally just screened to separate any clumps or weeds out. You’d use this aggregate in gardens to help nurture plants as this is the soil that contains all the nutrients your plants need to grow.

Ballast- You’d use ballast mainly in concrete mixes, it’s made up of a combination of crushed stone and sand. Sometimes you may also find some clumps of clay in ballast.

Sand- This aggregate is made up of stone that nature has ground down into fine particles over the course of a few thousand years! You’ll find sand used extensively in brickwork, driveways, and concrete mixtures.

Crushed concrete- This is a recycled aggregate used in similar applications to MOT Type 1, the only difference with this aggregate is that it is not certified. Beware- many companies sell crushed concrete as Type 1!

That concludes our guide to aggregate manufacture, hopefully, you’ve learned how aggregates are made and discovered some of their common uses. If you’d like to learn more, please check out our sources and related reading sections below and if you have any questions, you can leave a comment or contact the team here, we love talking rubbish!

Sources

https://www.kandbcrushers.co.uk/the-process-of-manufacturing-aggregate/

https://www.generalkinematics.com/blog/aggregate-manufacturing-process/

https://www.aggregate.com/blog/essential-guide-construction-aggregates

Further reading

https://www.sixtownswaste.co.uk/blog/how-demolition-works

https://www.sixtownswaste.co.uk/blog/what-is-construction-waste

https://www.sixtownswaste.co.uk/blog/skip-hire-v-grab-lorry-which-is-the-best-option-for-you

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