Crazing
A network of fine, shallow, interconnected cracks resembling cracked glass or dried mud, confined to the surface skin of a slab.
What does crazing mean?
Crazing is caused by rapid drying and shrinkage of the very top layer, often from finishing with water on the surface, curing that was skipped or applied intermittently, or a sudden temperature drop. It is cosmetic and does not affect structural performance, but it becomes highly visible when the slab is wet or when a sealer is applied. Once present it cannot be removed without grinding or resurfacing.
In practice
Crazing that was invisible on a dry garage floor suddenly shows up as a spiderweb pattern the day a sealer goes on.