I just did a project like that. Good luck! I tried a torch, just made a mess (smelled great too!) Then hadild success with a propane shop heater pointed at the floor this high amount of heat in a semi large area loosened a good amount. What I ended up with (and worked the best) I picked up a ice chopper at home depot filed it sharp and used my legs in sort of a digging/pushing motion. Saved money on going to the gym too!