Best for cleaning concrete shop floor

Remember that stuff eats the mortar! When we do concrete walls and we tried to give it that old look we'd peel the panels off a little early and put that acid on it. It's exactly what it sounds like , acid and it will burn through anything. Like your concrete floor!
that's why it works... taking a layer off and the stains with it. Do it too often and the cream of the concrete will be gone.