You wouldn’t think that concrete could be damaged by fire, but it can be. My client’s fire meted many things on top of his garage floor’s concrete. This caused a significant discoloration of the concrete’s surface, which could not be easily removed. The only solution was to replace the entire floor.
The following photos show part of that process. The first photo shows the damage floor, and the second shows the floor removed after it was jack hammered. I’ll post when the new floor is in so that you can see the difference.