Common Causes: A concrete floor dusts under traffic because the wearing surface is weak. There are at least five identifiable causes of dusting:

• Carbon dioxide from open unvented heaters, gasoline engines, ready mix trucks, etc.
• Premature floating and/or troweling especially when condensation from warm humid air forms on cold concrete.
• Inadequate or improper curing.
• Excess amounts of clay or silt in the concrete.
• Inadequate protection of freshly placed concrete from rain, snow or drying winds.

Prevention:

• Use low-slump concrete (4-inch max.)
• Do not perform any finishing operations with bleed water present on the surface.
• Avoid placement directly on poly or non-absorptive sub-grades.
• Use proper curing methods to retain moisture in concrete for the first 3-7 days.
• Use vented heaters.
• Open building for ventilation during production.

Repairs:

• Sandblast, shotblast or use a high pressure washer to remove the surface layer.
• Apply a commercially available chemical floor hardener, such as sodium silicate, metallic zinc, or magnesium fluosilicate to thoroughly dried concrete. If some dusting persists, coat with latex, epoxy sealers or cement paint.