What is the difference between landscape decorative rock and aggregate rock?

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Let’s talk about aggregate.

Firstly, what does the word mean?

The word ‘aggregate’ means a mass or group of things or fragments. But more specifically for our industry it is: 1) the sand or pebbles added to concrete, or 2) crushed rock added to some application for structure, like a paver patio sub-base. It comes from the Latin word ‘aggregat’ which means ‘herded together’.

When you think of aggregate, think about gravel bits inside concrete, gravel bases under a patio or walkway, and sand/pebbles/gravel under a road or gravel under a drainage system (such as a French drain). It’s a construction material that is used for structure, building, it is a ‘filler’.

What is landscape decorative rock?

When you think ‘decorative rock’, think about beauty, display, external, and landscape designs. It is used for visual purposes, to make things look good. Whereas aggregates are used for structure (internal).

What adds confusion to the mix (pun intended), is that some landscapers often also refer to decorative rock used in flower beds as ‘aggregate’, whereas they are actually referred to as landscape decorative rock in this use, since in this case they are being used for aesthetics as opposed to structure. In other words, the same rock can be called both terms.

Still confused?

No problem! Think of it like this, polished rock is decorative landscape rock often used in flower beds, and crushed dusty rock is usually used as an aggregate in building, but NOT always, as it can also be used as a decorative rock.

What are some examples of these types of rock?

As we stated earlier, the same rock can be used for both purposes, so here are some different types of crushed rock which can be used for decoration, or as an aggregate for structure:

Stone dust

A good footer for a retaining wall, but not for use for a sub-base for a paver patio.

21-A (crusher)

You want to use this for a paver patio: 3/4 granite with a smaller aggregate, and stone dust, when it is compacted down, you run plate tamper and it gets very yard.

Concrete sand

It is fine, but it is not strained thoroughly, and there will be small pebble-sized granules. Put this on top of 21-A, and then the pavers go on top.

Pea gravel

Used for Decorative landscaping, and exposed aggregate concrete.

River wash

Used as a draining system as a topper for a French drain, can also be used as decorative landscaping, patio, walkway; used to prevent weeds from growing.

River wash 1″

Because it’s bigger it doesn’t erode as much therefore it is good for patios and walkways.

River wash 4-6″

Used as dry stream bed, an area where you want to divert some water down into a stream.

Source:
[Phoenix Home Services Inc]
northernvirginiaconcrete.com

What does ‘aggregate’ have to do with concrete and cement?

The word ‘aggregate’ is frequently used in conjunction with ‘concrete’. In this case, the aggregate is the sand and larger crushed rock particles that gets mixed into a mix of cement powder and water. Cement it is the glue that holds aggregate together. Cement is a powder, if you mix it with water, it turns into a paste. The small rocks of the aggregate adds bulk to the paste.

What’s the point of the aggregate?

The cement paste acts as a glue to hold the aggregate together. You can just use plain cement and no aggregate, but it would cost more, so by using aggregate as a filler it costs less and is just as strong.

Also cement expands and contracts when hot/cold and dry/wet; by having aggregate, it reduces this so the cement cracks less.

Where should you get YOUR decorative landscape rock?

At Kalamazoo we have a wide selection of rock for your landscaping needs. Check out our catalogs, we’re confident we have the size and color that you need, no matter what type of project you have!