Exposed aggregate caused by surface deterioration

Possibly, and that is the first thing to establish. Exposed aggregate is a deliberate decorative finish, achieved by removing the surface paste while the concrete is young to reveal the stone. It is also what a worn-out surface looks like once the paste has gone.

The distinction matters because one is a finish to maintain and the other is deterioration to address, and they are told apart by uniformity rather than by the presence of stone.

What it is

In concrete, coarse aggregate is bound in cement paste, and the finished surface is normally paste with the stone below it. Where the paste is removed — by design, by wear, or by deterioration — the stone becomes the surface.

A deliberate finish is uniform. The exposure is consistent across the slab, the stone is often selected and rounded, and the profile is even, because it was done at once and on purpose.

Deterioration is not uniform. It concentrates where wear and weather have been worst — the wheel tracks of a driveway, the walking line across a patio, the bottom of a slope where water runs — and the exposure varies in depth across the slab.

What seeing this cannot establish

• The presence of exposed stone does not establish deterioration. Pattern does.
• The depth of paste loss is not readable from a photograph, and it matters because it affects both the remaining cover over reinforcement and how much material an overlay needs.
• Whether the loss is continuing cannot be established from a single observation.

What this can be associated with

Candidate explanations, not findings. Nobody can establish which applies to your concrete without seeing it.

• Long-term abrasion from traffic, particularly vehicle tyres on the same line
• Freeze-thaw and de-icing salt action removing surface paste progressively
• Water running consistently over the same area, which can be associated with paste loss along the flow path
• A weak surface layer from finishing or curing that abraded faster than sound concrete would
• Pressure washing at high pressure, which can be associated with accelerated paste removal

What you can safely check yourself

• Compare the affected area with a part of the slab that is sheltered or untrafficked — under a step, at the edge, beneath something that has always sat there. If that area still has paste, the exposure is wear rather than design.
• Check whether the exposure is uniform or follows a pattern of use. Wheel tracks and walking lines are the giveaway.
• Photograph both the exposed area and the sheltered reference area, in the same frame if possible.
• Feel whether the stone is proud of the surrounding paste. Progressive loss leaves stone standing above a receding paste level.
• Note whether the surface still sheds material when rubbed.
• Note whether high-pressure washing has been used on it.

When this is frequently cosmetic

• Even, stable exposure with no further material loss, particularly where it could plausibly be the original finish
• Light exposure in wheel tracks on a driveway that is otherwise sound and draining

When professional evaluation matters more

• The exposure is deepening between dated observations
• Coarse aggregate is becoming loose or coming out, leaving voids
• The slab is thin and paste loss is meaningfully reducing cover
• The surface has become uncomfortable or unsafe underfoot where that matters — a pool deck, a barefoot area
• Exposure coincides with scaling, pitting or crumbling, which together suggest broader surface failure

When replacement enters the conversation

• Aggregate is coming out rather than merely being exposed
• Loss is extensive and the remaining surface is not a sound base for an overlay
• Cover over reinforcement has been meaningfully reduced across an area

Evidence worth having before you ask for estimates

Every item here is something you can produce without tools or risk, and every one of them makes an estimate more accurate.

• Paired photographs of the affected area and a sheltered reference area
• A note of whether the pattern follows use lines
• Whether stone is proud of the paste, and whether any is loose
• A note of pressure-washing history and salt use
• The slab's age and, if known, its original finish

Questions to ask whoever comes out

• Is this the original finish or is it wear? What are you comparing against?
• If it is wear, has it stabilised or is it continuing?
• Is the existing surface sound enough to bond an overlay to, and how are you checking?
• Would sealing help here, or is there not enough paste left for that to be the right move?
• If we resurface, what happens where the aggregate is standing proud?

Where estimates for this commonly differ in scope

These are the places two prices for apparently the same work stop being comparable.

• Sealing, resurfacing and replacement all get offered for this and address it very differently.
• Surface preparation for an overlay on an aggregate-exposed slab differs from preparation on a paste surface, and estimates rarely say which they have priced.
• If the original finish was decorative, matching it in a repair is a specialist job and should be priced as one.

Who tends to do this work

• A decorative or specialty concrete finisher
• A concrete repair specialist

ConcreteOwner does not inspect, certify or approve contractors. This describes which trade usually holds this work, not a recommendation of anybody in particular.