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Exposed aggregate is much sought-after material for patios, swimming pools, pool decks, driveways, pathways, sidewalks, plazas, and steps. In this short read, we’re going to bring you up to speed with what this landscaping material is, what it costs, its pros, cons, and more.
When the top outer layer of cement paste is removed to expose the decorative aggregate below, we get what is popularly known as exposed aggregate concrete, These aggregates can be either seeded into the concrete mix or batched into it.
Commonly used examples of aggregates include decorative stones, crushed glass, gravel, crushed stones, pea stone, quartz, basalts, limestone, and granite. The texture of these aggregates could be either coarse or fine and can vary in size and shape as well.
The reason exposed aggregate concrete has gained such popularity as a landscaping material for various purposes is that it is durable, slip-resistant and has visual appeal.
Methods for creating exposed aggregates
There are multiple methods used to create exposed aggregates. Here’s a brief description of each of those methods.
- The most common method is called the standard type. This method involves mixing or batching aggregates into the concrete mix.
- The second method is called either topping or concrete overlay. In this method, the aggregates are first mixed into a concrete overlay batch before being applied on top of an existing concrete slab. This is the method used to refurbish an existing concrete slab by applying between an inch or 1.5 inches of aggregate mix on top.
- In the seeded method of creating exposed aggregates, the aggregates are placed by hand on the surface of freshly poured concrete and floated into it.
- The polished method, also known as honing, is the most commonly used method when you want to use exposed aggregates on interior surfaces. This method is like a mix between topping and the standard method.
In this method, the top layer of concrete is either ground or sanded until a natural stone and flat matte finish has been achieved.
To expose the aggregates in the concrete, the top layer is often sprayed with water and then the thin layer of cement paste is brushed until the aggregates are visible.
Alternatively, another way of achieving the exposed aggregate finish is when the top layer is sprayed with a surface retardant that slows down the curing while the layer of concrete below hardens. The top layer is then washed off to expose the aggregates.
How to seal exposed aggregate concrete
It is essential to seal exposed aggregate concrete to protect it against damage by spalling, freeze, thaw, dusting efflorescence, abrasion and staining. Sealing the concrete also highlights and enhances the colors and depth of the aggregates. This is achieved by choosing a sealant with a high gloss, wet look.
While choosing a sealer for the aggregate concrete, it is important to keep in mind that the sealer ought to be UV resistant, nonyellowing, and capable of repelling oil, water, grease, and stains.
Experts work with either one of the two following exposed aggregate sealers:
- Water repellent concrete sealers work below the surface, helping the concrete aggregates repel water as well as avoid staining and deterioration. This sealer has a lifespan of around 7-10 years and does not alter the appearance of the aggregates.
- Acrylic concrete sealers bring out the depth and colors of the aggregates by giving them a glossy, wet look. While they do protect the concrete against dusting, staining, water and can be used on both cured and uncured concrete, the sealer will have to be reapplied every one to five years.
Pros of exposed aggregate concrete
Exposed aggregate concrete as decorative concrete is a great fit for patios and other outdoor uses because it has such great visual appeal. Not only is it sure to add to your home’s curb value, but it can also easily match with practically any architectural style and exterior decor.
Read more: Best plants for curb appeal
Exposed aggregate concrete is basically concrete. Just because it is a decorative variety does not mean it lacks any structural integrity. In fact, it has been known to last 40 years or longer, which makes it more durable than stamped concrete, which is another type of decorative concrete.
Even under wet conditions and under the duress of heavy foot traffic, the texture and anti-slip qualities of this material ring true, making your patios and pool decks that much safer during the rains as well.
Exposed aggregate concrete is capable of dealing with all kinds of extreme weather conditions.
Exposed aggregate concrete patios are easy to install and the material itself is not very expensive.
Maintaining exposed aggregate concrete surfaces is fairly simple. The surface will need to be cleaned with water regularly and re-sealed every three to five years to maintain the glossy appearance.
Cons of exposed aggregate concrete
If not installed properly, the exposed stones and other aggregates in the material are liable to be damaged, causing severe problems in the long run. Moving heavy furniture over the surface and water are just two of the things that could damage the aggregates and cause pitting on the surface. Once the top layer is damaged, the rest of the concrete breaks down easily.
Difficult to repair
The most difficult part of repairing this material is blending in the patched aggregates with the already existing floor.
Maintenance needs to be regular
Maintaining exposed aggregate concrete needs to be a regular activity. You will need to clean the surface with a wire brush and a powerful hose to clean all the dust and grime off and keep it ship shape.
Exposed aggregate patios costs
The average cost of the material itself varies from $1.90 to $2.18 per square foot, with the national average being $2.04. At those rates, the cost of materials alone for a 100 square foot patio would cost you between a low of $125 to a high of $235, depending on the quality of materials you choose.
Labor will add between a minimum of $150 to a maximum of $500, depending on where you live and how experienced your concrete contractors are. This will bring the total cost of a 100 square foot patio to between $275 and $735.