Limestone floor Phil 25 Feb 2012 11:35 EST

Hi guys i'm working on a limestone floor on the second floor of a large building and the limestone is slowly pitting and the holes are full of powder 12 yrs old no coatings. Most of the floor when I tap it sounds like a dull thud not hollow but not crisp like other areas. Could this be from vapor Or poor mix on setting? All areas are the same, two floors
I'm just cleaning and filling for now but would like to sell some testing also. Thanks Phil  pic to follow
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