A porous or reactive stone near the surface, such as some cherts, shales or iron-bearing particles, swells from freezing, ASR or chemical change and pushes out a conical chip, usually 1/4 in to 2 in across. Split fragments of the guilty stone usually sit at the base of the crater, which separates a popout from scaling or a spall. Popouts are mostly cosmetic but point to an aggregate quality problem on exterior work.
Driveway's got popouts all over it, and every one has a busted piece of chert at the bottom.
Also heard as
- pop-out
- pop-outs
Related terms
Aggregate
The sand, gravel and crushed stone that make up 60 to 75 percent of a concrete mix by volume.
ASR
Alkali-silica reaction, a slow internal reaction between cement alkalis and certain aggregates that cracks concrete.
Scaling
Thin patches of surface mortar coming off a slab, usually after freeze-thaw cycles with deicing salt.