Reddit reviews Bean-e-doo Mastic Remover 1 Gallon by Franmar Chemical

I can help you with this. The secret is soybeans. Actually, a mastic remover made of soybeans:

https://www.amazon.com/Mastic-Remover-Gallon-Franmar-Chemical/dp/B0006NL1JA

Kind of expensive, but it saves so much time that it actually becomes a bargain. Melts that stuff like butter, and cleanup is easy. I used a wet vac to suck up most of it, and then wet it over twice more with hot water and then the vac. Once done, you really could not tell it was ever there.

This really depends on two major factors: 1) is the mastic primarily ON the concrete or soaked INTO the concrete, and 2) what you will put over the concrete floor as subfloor or final finish.

Solvents work best, but are toxic, smell bad and you should really be wearing a half face respirator with proper cartridge when using the stuff. Effective yet a pain to work with.

Here is an example:
http://www.zoro.com/value-brand-low-odor-asbestos-mastic-remover-5-gal-3uac3/i/G4330952/?utm_source=Bing&utm_medium=cpc&utm_campaign=PLA

and another

http://www.cronincompany.com/MSDS/Parabond/Parabond%20Detach.pdf

Lots of folks want to ‘go green’ and use either a soy or citrus based alternative.

These work, just not as well. The main drawback here is you may need multiple applications, and still need to scrape the most stubborn patches.

Soy based includes the one mentioned below – it has various brands including Franmar (mentioned below), Seal Green and others

http://sealgreen.com/Mastic-and-Adhesive-remover-for-concrete.aspx

This product also used to be called Bean-e-doo (soy bean). It works, but – in addition to the drawbacks listed above – it does leave a residue which may make future glue-on finishes very difficult. These complaints, and others, are listed here:

http://www.amazon.com/Bean-e-doo-Mastic-Remover-1-Gallon/product-reviews/B0006NL1JA/ref=cm_cr_pr_viewpnt_rgt?filterByStar=critical&pageNumber=1

The citrus and soy based products work (though you often need to buy twice as much as the mfrs recommend to get the job done). Also, they work best for mastic that is primarily ON the concrete, not for the stuff that has deeply penetrated; you need a harder solvent for that issue.

The other person mentioned leaving it in place and laying new product over (e.g. pad and carpet). I am guessing there is a reason you don’t want to do leave the mastic, so I provide another option: seal it.

Concrete mastic (‘thin set') or especially a polymer-enhanced concrete leveler (parabond, red devil) are possible good options. You don’t want to use these if you apply a water sealant to the concrete (some folks seal basement concrete for water intrusion issues), but otherwise they have many great applications.

don't be shy to call the manufacturers (DAP, para-chem) for the best application/product for your situation; they can be very helpful...

It is up to you. I personally would use mastic remover: https://www.amazon.com/Mastic-Remover-Gallon-Franmar-Chemical/dp/B0006NL1JA, remove it with a shop vac after it has dissolved, and then lay the planks over it.