Concrete popouts

A popout is exactly what it looks like: a particle near the surface increased in volume, and the thin cover of concrete above it had nowhere to go but off. The cone-shaped crater with a fractured aggregate particle at its base is the signature, and it is one of the more specific patterns concrete produces.

Individually they are almost always cosmetic. What is worth reading is the pattern — how many, how large, whether they are still appearing.

What it is

Some aggregate particles absorb water and expand, or contain material that reacts and expands. When such a particle sits close to the surface, the expansion breaks the thin layer of concrete covering it and lifts a conical piece away.

The crater is characteristically shallow, roughly circular, and wider at the surface than at depth — a cone rather than a hole. The offending particle is often still visible at the bottom, sometimes split.

Size tends to track the particle size. Fine aggregate produces small popouts a few millimetres across; larger stone can produce craters an inch or more wide.

What seeing this cannot establish

• A popout tells you about one particle. It says nothing about the strength or durability of the slab as a whole.
• Popouts and small spalls look similar to a casual glance. The cone shape and the particle at the base distinguish them, and it matters because spalling has different associations.
• Whether more will appear cannot be predicted from those already present, because it depends on particles you cannot see.

What this can be associated with

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

• Aggregate particles that expand on wetting, or that contain reactive material, sitting close to the surface
• Freeze-thaw cycling, which can be associated with popouts appearing at a particle that has taken up water
• Insufficient cover over coarse aggregate near the finished surface
• Exposure to persistent wetting, which gives absorptive particles the water they need to expand

What you can safely check yourself

• Look at the shape. A cone wider at the top than the bottom, with a particle at its base, is a popout rather than a spall.
• Count them over a measured area — say a square metre — and note the figure. Density is more informative than the presence of a few.
• Photograph a representative crater close up with something for scale, and the wider area for pattern.
• Note whether new ones are appearing. Mark the existing ones with chalk and check back after a freeze-thaw season.
• Note whether they concentrate where water sits, which supports a wetting association.
• Check whether anything catches on them — a bare foot, a mower wheel, a shovel.

When this is frequently cosmetic

• Scattered small popouts in an exterior slab with no other surface deterioration
• Popouts on a driveway or utility slab where they are visible but nothing catches on them

When professional evaluation matters more

• Popouts are numerous and dense enough that the surface is becoming rough or losing material generally
• New ones continue to appear season after season
• They coincide with scaling, spalling or a dusting surface, which together suggest a broader durability question
• They are on a surface where a smooth finish matters — a pool deck, a barefoot area, an interior floor

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.

• A count over a measured area, with the area stated
• Close-up and wide photographs
• Chalk marks on existing popouts and a dated follow-up photograph
• A note of whether the area stays wet and whether salt is used
• The slab's approximate age

Questions to ask whoever comes out

• Are these popouts or small spalls, and does the difference change what you would do?
• Does the density here justify doing anything, or is this cosmetic?
• If patched, will the repairs be visible?
• Would you expect more to appear, and does that affect the timing of any resurfacing?
• If I resurface, does the existing surface need any specific preparation because of these?

Where estimates for this commonly differ in scope

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

• Individual patching and resurfacing an area are very different prices for what a homeowner may describe the same way.
• Where popouts are dense, an estimate may propose an overlay. That is an appearance and durability decision rather than a repair of the popouts.
• Colour and texture matching for individual patches is rarely promised explicitly and rarely achieved perfectly.

Who tends to do this work

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

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