I accidentally used quickcrete mortar instead of concrete for my countertop. I didn't even notice when pouring it into the mold, the consistency was the same as the concrete sample I had made. It is obviously not sanding down like the sample did. It's sanding down much faster and it's not as hard. My question is...can I sand it down and apply a skim coat of concrete on top of the mortar and resand and finish? How will this hold up?