Exposed aggregate: how the finish is actually made

Exposed aggregate is a decorative finish where the cement paste at the surface is removed to reveal the stone in the mix. Blasting is one way to achieve it, and the control you have over depth is the whole skill.

Three depths

• Light etch. Just the surface paste removed. A subtle texture, mostly used for slip resistance.
• Medium exposure. The tops of the aggregate visible. The most common decorative choice.
• Deep exposure. Stone standing proud. Dramatic, but it needs enough cover in the original pour or you undermine the aggregate.

What decides the result

Media, pressure, standoff, and how consistently the operator moves. Uneven technique on a decorative slab shows permanently as banding or blotching, which is why a test area matters more here than almost anywhere else.

The mix matters more than the method

You can only expose the stone that is in the pour. A slab with fine aggregate will never look like one with river rock, however deep you go. On existing concrete, what is in there is what you get.

Common on driveways and walks through Ross Glen, Southridge and Crescent Heights, and it is the finish people most often damage by hiring pressure instead of technique.