The dust that goes away on its own
Fresh concrete finishes its cure over weeks, not days, and a fine dust the first couple of times you sweep a new slab is part of that. It thins out and stops within the first month as the surface fully cures. That is normal, and it is not the same thing as a slab that keeps producing powder long after.
The dust that does not stop
True dusting is a weak, powdery top layer that wears away under normal use and keeps coming back no matter how often you sweep it. It usually traces to bleed water or laitance, the thin, weak film of cement and fines that rises to the top of the slab, getting troweled back into the surface instead of allowed to leave. A surface finished with too much water in the mix, or troweled too early while that water was still working its way up, ends up with a top skin that never had the strength the rest of the slab has.
- Dust that fades out over the first month: normal curing
- Dust that keeps returning under traffic: a weak top layer
Why the cure itself matters here too
A slab that dries out too fast in its first day or two, especially in sun and wind, cures into a weaker top layer even when nothing about the finish was rushed. That connects dusting back to the same early curing window that governs cracking and color, just showing up as a powder underfoot instead.
A wet cure, keeping the surface damp through those first critical days rather than letting it flash dry, gives that top layer the water it needs to keep reacting instead of quitting early. Skipping that step on a hot, windy pour day is one of the more common, and more avoidable, ways a slab ends up with a soft skin.
What actually helps, and what only covers it up
A sealer or a cure and seal product can hold down surface dust on some floors by binding that weak top layer together. It is a real help, but it is not a fix for why the surface finished soft in the first place. Getting an honest answer on that takes someone looking at the slab, not a guess over the phone.
Where dusting shows up most often
Garage floors and basement slabs dust more visibly than a broom finished driveway does, mostly because tires and shoes track the powder onto a floor you look at every day instead of leaving it out where wind and rain carry it off. That does not mean an outdoor slab cannot have the same weak top layer. It is just harder to notice until it starts feeling rough or chalky underfoot.