Dusting
A powdery, chalky surface that rubs off a hardened slab under traffic, caused by a weak top layer that never properly hydrated or was diluted with water.
What does dusting mean?
The usual causes are finishing bleed water into the surface, sprinkling water to ease troweling, inadequate curing, and carbonation from unvented heaters burning fuel inside an enclosed space during winter placement. The weak layer is thin, so grinding or densifying can often salvage the floor. Dusting is a finishing and curing failure, not a mix strength failure.
In practice
A new garage floor leaving white powder on shoes and tires had its surface ruined during finishing, regardless of what the cylinders broke at.