I have an old concrete patio in the back of my house. This patio has until recently been covered by a small deck, but for several reasons I've decided to replace the deck with synthetic outdoor flooring material that can go on top of the concrete, sitting on top of plastic grid stand-offs. Unfortunately it requires is that the underlying stratum be reasonably smooth.
Having removed the old deck, I've discovered that the concrete has an old iron pipe embedded within it, as can be seen in the attached picture. The pipe is clearly disused - one end of it is open to the elements. I suspect that there used to be, or still is, a heating oil tank under the patio, as is common in my part of the world, and the pipe connected to it. I have no idea what would compel someone to just pour a concrete pad and ignore the pipe (never mind decommissioning the oil tank itself), but there it is. The pipe is quite substantial - the metal is some 1/4 inch thick, and the part above ground is about 18 inches long.
The pipe presents a challenge to my plan of laying down the plastic flooring onto the patio, since it protrudes about an inch and a half at highest, and will surely interfere. I am trying to figure out a way to get rid of the metal, that does not involve busting out the concrete and pouring it anew.
My best idea so far has been to fit a cut-off disk into my angle grinder and cut around the "water line" of the concrete around the pipe. I tried it out and it was a failure - the metal is thick enough that my 4.5" grinder and thick-ish cut off wheel just get bogged down. I plan to try again with a thin cut-off wheel, but I am not super-optimistic. I've also considered renting out a big concrete saw and cutting out the area containing the pipe - however I don't think it would be a good idea to use the saw to cut through the pipe itself given its thickness, and given that I can't see where the pipe is under the concrete, that could involve taking out a substantial part of the patio to be safe, which would also interfere with my plans.
Are there any other options I could consider here? I am willing to borrow or rent tools to accomplish this safely (and hopefully quickly).