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Our concrete is dusty. What can we do? Print E-mail
Chalking or powdering of the concrete slab is called dusting. These surfaces typically powder under any kind of traffic and can easily be scratched by a nail or even by sweeping.

The concrete floor will dust as the wearing surface is weak.  This can be caused by any of the following:

  • finishing applied when the bleed water was still on the surface (reworking water back in to the top 6mm of the slab produces a very high water to mortar ratio and therefore a low strength layer)

  • floating or trowelling in of condensation in to the concrete (per above)

  • inadequate ventilation of confined spaces where engines or other sources of carbion dioxide are present.  The presence of CO2 may cause a chemical reaction known as carbonation, greatly reducing the strength and hardness of the concrete.

  • insufficient or no curing, leading to a very soft surface skin which easily dusts

  • inadequate protection of the fresh concrete from wind, snow, etc which hinders proper curing

If you have dusting on your concrete, there are a few things that you can do to alleviate the symptoms.  Please note that this will not fix any strength issues in the concrete slab, only the surface dusting.

You can apply a chemical floor hardener such as zinc or magnesium flurosilicate per the instructions that will come with these materials.  If the dusting persists, use hardeners with cement properties.

In severe cases, you can wet-grind a concrete floor and then reapply a top layer of cement which should bond properly.