The following video shows how to safely remove Black Mastic from a Concrete floor.  

For more information on SealGreen visit SGR1500 Mastic and Adhesive Remover for Concrete - With Oil Cleaner/Degreaser

For more information on the SealGreen Mastic Remover Tool Kit visit - Tool Kit

Video - https://youtu.be/He3Xn3B1fuQ