My workshop/storeroom was an extension to my house, and the thick concrete slab floor is slowly crumbling away as I walk around.

I've tried using a vacuum cleaner, but honestly I could literally suck up the entire slab if I kept going.

Is there a way to seal the concrete to bring the floor to a semi flat surface again?

The two options I've thought of are

1. Wet the floor and lay another layer of concrete to level it and to stop the crumbling.
2. Try use liquid polyurethane to both level out the uneven surface and to stop the crumbling.

I'm wondering what the best way is to go about this?

I don't actually need/ want to do the entire area as I have heavy workbenches etc that I made large than the door.... And have nowhere else to temporarily store things. Just need to do + - 8sqm in the middle of the floor.

Thanks!