If I had a better shop I would leave the floor concrete. Mine has a wooden floor which doesn't allow me to grind indoors. ( isn't a problem in summer but this winter could be a hassle ). Place a few rubber mats as Stan says and you should be OK.
Most of the knives I've made that have had flaws were junked. One became my shop knife. If it has a flaw that I know is there I just can't sell it. Thats why its taken me so long to finish knives, I'm trying to get them the best they can be.