DIY & Home Improvement

Elbow grease and razor blades.

Go to a "flooring supply store" If you PM me your zip code I'll find you one near by.

What you want to ask for is a "stand up razor scraper" and a box of 8-10 inch blades.

They sell ones that are small that you use on your hands and knees with a 4 inch blade, but unless its a very small area your back and knees will be glad you spent a few bucks more on the "stand up" ten inch version.

Then scrape scrape scrape changing blades often. For heat you can try a blow dryer or rent a "heat gun"

You may even be able to rent the scraper.

DO NOT under any circumstances use "Something that can be mopped on that will penetrate and dissolve the glue" if you plan to adhere anything (even stain) to the floor anytime soon. It may not seem like it but concrete is very porous and anything that will dissolve the adhesive will prevent anything new from sticking to it.

If you plan a new floating floor, then go for the adhesive remover. Make sure you're well ventilated!

PLAN B: Find a flooring installer with the proper tools to send his apprentice over to do it. Expect to pay about $25 an hour for this depending on where you live.

On edit: Tip the apprentice, he's likely making $10 an hour or less.