Making screw in concrete hold better

[ATTACH]79105[/ATTACH]I need help identifying this small piece of hardware. There are two on my laundry room wall and would like to know what it was used for.

Greetings and salutations. First timer here and I've got an issue. Years ago my father had a friends son do some work in the basement. This included laying down some vinyl floor tiles. The guy doing the job over engineered the crap out of it to the point where he used Tapcom (I'm assuming they're Tapcom cause they're blue) masonry screws to adhere the 3/4" plywood to the concrete slab. The tiles were then glued to the plywood. Well, recently we had to have that flooring pulled up and that left behind a veritable sea of blue screw heads. I have a Porter Cable oscillating tool and gave it a try to remove the screw heads. It took me three wood/metal blades and two "grinding" attachments to get through 5 or 6 screw heads. The wood/metal blades were literally removed of teeth and the grinding attachment lost all of its grinding compound. I'm thinking these screws are made from depleted uranium of something. Has anyone gone through something like this? Would an angle grinder be a better option? Thanks. *EDIT* The screws have a Phillips head, not the hex head and the Philips head is full of dried adhesive. As a result, we can't back them out with a driver.