Exposed-aggregate concrete offers a timeless concrete finish that’s as beautiful as it is practical and durable.
This decorative style of custom concrete is common here in Whatcom County; you’ll see it most often on patios, driveways and retaining walls. Because it makes a good non-slip surface, you might even see aggregate concrete on the rare Bellingham pool deck.
There are several methods concrete contractors use to get the job done, but they all have important similarities.
How does the aggregate get into the concrete?
You can either have the concrete mixed with aggregate before it’s poured, or you can work the aggregate into the surface — this is called “seeding” the concrete — after it has been poured and finished.
One benefit of seeding concrete with aggregate is that a wider range of aggregate colors and styles are available. In fact, you could even choose something other than gravel to seed the concrete with, such as beach glass or coins.
Project feature: Aggregate concrete patio
increases usability of garden area
How is the aggregate exposed?
Essentially, when you create exposed-aggregate concrete, you’re removing the surface layer of concrete paste to reveal the aggregate underneath.
After the concrete is poured and finished and the aggregate is in place just under the surface, the next step is to remove that top layer of mortar. This is typically done in one of three ways:
- The first method is to wait until the concrete is hardened just enough to keep the aggregate embedded in the concrete and then brushing or washing the surface mortar away. This method requires precise timing and is best for smaller aggregate concrete jobs.
- The second method requires a chemical retardant that keeps the top layer of mortar from hardening when the rest of the concrete sets. This allows concrete contractors up to a day, typically, to remove the top mortar layer. The chemical spray must be applied immediately after the concrete is poured and finished.
- A third method for aggregate exposure is sandblasting after the concrete has hardened, but this isn’t done often, as this method can damage the aggregate in addition to removing the mortar.
Whatever the method, the end result is a classic decorative style of concrete evocative of old-world cobblestone or mosaic paths.
Custom Concrete Contracting services all of Whatcom and Skagit counties, including Blaine, Lynden, Ferndale, Bellingham, Mount Vernon and everywhere in between. For help with your next aggregate concrete project, please give us a call.