I presume you are referring to the expanding bolt type where a stud protrudes from the floor? I don't believe there is any easy way to remove these other than to break out the concrete to allow extraction- but this depends on the type of fixing involved. Some of the older Rawlpbolts had a heavy steel casing which tended not to deform (unlike some modern counterparts) when being tightened insitu. Simply loosening the nut and tapping the projecting stud was sufficient to allow extraction and reuse of the fixing. Try it and see! The quick solution of course is to cut the stud off flush with the floor using a cut off disc in a grinder, any remaining stub can be punched below the surface with a hammer and punch.