I am preparing concrete slab surface for leveling it. I removed the tiles first, and grinded away the remaining thinset mostly nearby the boundary of tiles. Here is the picture of the current situation:
The white area is where the grinder touched. The dark area is the original surface of the slab. My questions are:
1) Should I also grind the dark area to expose fresh surface?
2) If I do not grind the dark area, will it affect the leveling process and quality using the floor leveling compound? I remember before pouring the leveling compound, the concrete surface needs to be sealed. Will the dark area affect the sealing procedure?