Cheryl's Guide to Concrete Contractors

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Three Important Stages Of Installing Exposed Aggregate

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Whether you're building a new patio or resurfacing a driveway or path, installing exposed aggregate is a great way to add colour and texture. Here are three stages in the process.

Choosing Aggregates

Your choice of aggregates is crucial. Consider the colours of your home and the landscape when making your decisions to coordinate the surface with your environment. The hues of crushed natural stones such as limestone, quartz and granite depend on their origin—offering choices including delicate rose quartz, dark blue granite and charcoal limestone. Rocks, river pebbles, coloured glass and seashells are all options. 

The size and shape of the embellishments affect the final result also, both aesthetically and functionally. Rounder decorations create a smoother surface, while angular objects add texture. Ask your contractor about the best size and shape for your project. Some are better than others for around swimming pools, for instance, where you need a surface that is barefoot friendly while also providing traction.

Laying Aggregates

When constructing your driveway or pool deck, the contractors will submerge the aggregates within the cement. They might seed them into laid unset concrete, placing or sprinkling the elements by hand or shovel, before pushing them underneath. Alternatively, you can choose to combine the decorative pieces within the cement mixture before laying. As the aggregates disperse throughout rather than near the top, this technique uses more, which can increase costs. If you favour this method but want economy, you can lay an exposed aggregate overlay on top of a plain concrete slab. Because the overlayer is thinner, this works best with smaller embellishments.

Exposing The Aggregates

After adding the coloured pieces, the contractors wait a period before removing the topmost cement to reveal and bring the decorations to light. Using water and a broom, they spray and brush the exposed aggregate. Timing is crucial—too soon, and it will dislodge the pieces. Too late, and the mortar will be set and immovable. Spraying a surface retarder can delay the setting process, providing an extended window of time to remove the topmost mortar, sometimes up to 24 hours. An alternate method is sandblasting, which erodes the surface. This can dull and roughen the aggregates, however. Though at the same time, it increases traction for an exceptionally non-slip surface.

The main advantage of exposed aggregate is that it has the durability of concrete but with added visual interest to enhance and complement your home and landscape. And you can create a wide variety of textures and colours by selecting between aggregates.