I know that dusting -- the development of a powdered material at the surface of concrete -- is associated with weak concrete at the surface. I've also learned several ways to prevent dusting during new construction. However, besides grinding the surface, I've never heard of any methods to correct dusting once it has occurred. Are there any?
According to ACI 332, "Guide to Residential Cast-in-Place Concrete Construction," dusting can be remedied by applying dilute solutions of a floor-sealing product based on sodium metasilicate (water glass) or silicofluorides. When using water glass, apply three or four coats, allowing the previous coat to dry before applying the next coat. For the first two coats, use four parts water to one part silicate. The third coat should be a 3-to-1 solution. The treatment is completed as soon as the concrete surface gains a glossy finish. Zinc, sodium and magnesium silicofluoride sealers are applied in the same manner as water glass. These compounds can be used individually or in combination, but a mixture of 20% zinc and 80% magnesium gives excellent results. For the first application, dissolve 1 pound of silicofluoride in 1 gallon of water. For subsequent coatings, use 2 pounds per gallon of water. Mop the floor with water shortly after each coat dries to remove encrusted salts. It is important to note that sealing products will not convert a poor-quality floor into a good-quality floor. They simply are a means of upgrading a dusting floor while improving its wear resistance.