Q: I try to do things right, and I've never had a dusting floor before, but now I do. What caused it?

A: Check the following possibilities taken from ACI 302.1R-80, "Guide for Concrete Floor and Slab Construction":

  • an overly wet mix
  • floating or troweling bleed water into the surface
  • clay, dirt or organic materials in the aggregate
  • water applied to the surface during the finishing process
  • using unvented heaters to protect new concrete from cold weather
  • inadequate curing, especially if the weather was dry