Exposed aggregate is a very popular type of concrete nowadays. Its wide array of styles and colour/pebble combinations makes it very attractive to suit both classic and modern homes. As opposed to other types of concrete, exposed aggregate is both a decorative type as well as practical. It is highly durable and slip-resistant, adding an extra layer of ease for the wetter seasons. But what is actually involved in the process of laying down an exposed aggregate driveway?
Selecting the aggregates
As I’m sure you’ll want your driveway to look the part as well as work the part, this is an important stage. The aggregates are the minerals that will give the concrete its colour and aesthetic. You can basically combine an endless amount of minerals to achieve the look you’re going for, whether it’s to match a certain part of your front yard or to just completely contrast it.
This is when you’ll also be able to choose the shapes, how smooth they’ll be, their opaqueness as well as their texture. Remember, there is an almost countless number of combinations that you can utilise when it comes to exposed aggregate driveways, so take your time and think about what you want because chances are it’ll be able to be done.
Pouring the base
Now that you have your aggregate selected, the base can be poured and spread. This is a standard concrete pouring technique except you’ll want to leave the top inch unfilled for now. Continue to fill your concrete forms up to a ¼ of an inch from the top layer. The reason we leave an inch on top is for the aggregate and stones to be put in later.
You’ll want an even surface on top. This is a process that involves a lot of patience and careful work – if you overwork it then it will result in an uneven surface. So, make sure you screed the surface very carefully to achieve a smooth and even layer.
Thick, soft cement is the aim of this part. You’ll want the surface layer to be mostly hard, but not too hard that you won’t be able to press the aggregates into it in the next step. All moisture must be cleared from the concrete forms to be able to move on so keep an eye on moisture build-ups. If your concrete is uneven, then it will show when the water builds up more so in the lower area.
Forming the top layer
Now it’s time to start making the real magic. Grab a bucket full of pea gravel and lay it over the cured cement. The desired outcome should be for the gravel to simply sit on top of the cement, it should not sink without applied pressure. Spread the gravel using a brush. The gravel must be spread across the entire form and cover the cement entirely.
Pressing the stones
This is when you start to see the decorative side of the exposed aggregate driveway come to life. Take a piece of wood and begin pressing and tapping the gravel into the concrete gently. This is the stage where you’ll visibly start to see that some areas do need more gravel so don’t be afraid to add some.
The concrete will have hardened much more by this point. You can start laying down the mortar on top of the pushed down stones now, but it is imperative that there are no build-ups of mortar and that it is all evenly spread across the concrete form. Use brushes with hard bristles to distribute the mortar whilst still tapping the stones further into the concrete.
You will need to use a gravel rolling machine to then roll the gravel over the forms. As long as you don’t stamp your feet hard on the surface or twist your heels, you’re able to walk on top of the forms at the stage. The purpose of this is to compress the gravel and mortar as much as possible in preparation for the final stage.
Exposing the aggregate
This final step will utilise a combination of water pressure and brushes/brooms to achieve the desired outcome. Use a broom or brush to go over the concrete form, exposing the aggregate beneath. Using a hose at a low angle is the other part to this. The pressure of the water will chip off the mortar, leaving the aggregate to be exposed. If any of the pebbles are dislodged, then stop and wait for a while before continuing.
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