In cold weather the concrete sets slowly, particularly cold concrete in below grade placements. If relative humidity is high, water will condense on the freshly placed concrete. This water condensation, if troweled into the surface, will cause dusting. Inadequate ventilation in close quarters. Carbon dioxide from fossil fuel heaters and engines will cause a chemical reaction upon the surface of the fresh concrete known as carbonation.
Carbonation greatly reduces the strength and hardness of the affected concrete surface.
Last, Inadequate protection of freshly placed concrete from the elements, rain, snow, wind. To prevent dusting, use concrete with a moderate slump. However, concrete with a higher slump may be used providing the mixture is designed to produce the required strength without excessive bleeding or segregation. Never sprinkle or trowel dry cement powder into the surface of fresh concrete to absorb bleed water. Remove bleed water dragging a hose across the surface.