After removing Bootcamp, my Hard Disk has around 80GB missing
I'm guessing that OS X probably mis-partitioned it when removing the Bootcamp partition, and the old Windows partition is either free space or corrupt. Either way, you can try to go to Disk Utility or boot into Recovery(like @klanomoath said) and check to see how the partitions are setup. You can then resize the Macintosh HD to use any free space, and erase any corrupt or unneeded partitions.