Honeycombing
Voids in hardened concrete where the paste failed to fill between stones, leaving a rough, open, rock-pile appearance. Usually caused by inadequate consolidation.
What does honeycombing mean?
Honeycombing at the surface is often a symptom of deeper voids that compromise cover over reinforcement and open a path for water and corrosion. Contributing causes include harsh mixes, congested rebar, dropping concrete too far, leaky forms that let paste escape, and simply skipping vibration. Repairs range from patching cosmetic areas to structural evaluation when the voids are extensive.
In practice
It shows up the moment the forms come off a wall, and how deep it goes determines whether it is a patch or a problem.