Dusting refers to the formation of a loose powder caused by the disintegration of the top surface of the concrete due to an extremely weak surface. Some causes for dusting might be: Finishing operations are performed while there is bleed water on the top surface of the slab. Concrete was not properly cured resulting in an extremely weak surface. Concrete was exposed to carbon dioxide while still in plastic state. Below are some ways to reduce the likelihood of such problems:
-Don’t finish concrete while bleed water is on the surface. When bleed water is worked back into the surface it elevates the water/cement ratio of the surface layer which dramatically reduces the surface strength.
-Proper curing practices as soon as possible and for proper period of time
-Avoid placing concrete on vapor barriers since they can extend the bleeding period into initial set/finishing period
-Ensure that if heating devices are used, room/building is properly ventilated to avoid carbon dioxide buildup while concrete is still plastic.
-Adding water to concrete can weaken the surface and increase dusting problems.