We did one at the beginning of the year, first I would test to make sure there in no asbestos in the black mastic. If it clears testing then its going to get messy, cover everything and make sure that you include post cleaning in your estimate. We used 9" grinders with vac ports attached to concrete vacuums.
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http://www.jondon.com/equipment-acc...r-prep-equipment/concrete-vacuum-systems.html) you can rent the set up at home depot but the vacuums are all beat up to hell and you still make a mess. Make sure you cover the smoke detectors or you will get a visit from the fire department (we did at 8 pm). It took 4 guys about 10 hours to grind about 600 square feet and 4 ladies and a guy 6 hours to clean up the mess. Also make sure you have knee pads because all of it is done on your knees. Or you can sub it out to a concrete guy that have the a 30K machine.
http://www.vanguardconcretecoating.com/diamond-grinding.htm