Exposed aggregate is created by removing the top layer on concrete from a surface to reveal the texture and colors of small stones underneath. This type of pavement is more unique and ornamental than a flat concrete slab, but it also has several disadvantages to consider before installing it.
Exposed aggregate can be as strong and durable as the concrete that holds the aggregate together, but the decorative stones on top are more vulnerable to damage. Harsh weather, heavy objects and water damage can loosen or dislodge surface stones, leaving rough pits in the surface. Once the aggregate begins to wear away, the damage spreads quickly as surface water weakens the bond between the aggregate and concrete.
Patching a section of exposed aggregate is more complicated than repairing cracks in concrete. The biggest challenge is blending in the patched surface with the rest of the pavement. Consider tinting the concrete patch compound to match the older concrete, and then fill the hole as you would with a concrete surface. Instead of feathering the new concrete over the surrounding area to level it out, only add enough compound to fill the hole. Then pack stones into the new concrete. Take the time to find to find aggregate that matches your existing surface as closely as possible.
There are several ways to install exposed aggregate, and each method has its own challenges. The oldest way to expose aggregate involves using a brush and broom to remove the top layer of mortar. You must work carefully so you don't overexpose the aggregate or loosen the concrete bond. Another common method is using a chemical surface retarder to delay the set time for easy surface removal. But this method exposes your lawn and plants to harsh chemicals.
Cleaning exposed aggregate is not as simple as hosing off a concrete slab. Debris and dirt get compacted between the textured surfaces, requiring a wire brush or strong hose to remove. Whether the surface is a driveway, walkway or patio, sealing it every two years will dramatically increase its strength and longevity.