While I was King of my Condo association we had a similar problem with a wrecked public sidewalk in front of our building. One call to my city councilman and the next morning the City road crew was on the job digging up & replacing heaved sidewalk.
They really hate it when peds fall down and sue the City.
It’s good enough. The only issue is the switch, check that you find the switch comfortable to use, I have a cheap grinder and the switch is getting hard to use, but the thing cut through a cast iron bathtub easily enough.
My neighbor had the same problem years ago. He got a guy with a backhoe to yank it out of the ground and toss it in the woods behind his house. It’s still there waiting for some future historian to figure it out.
Unfortunately you have a metal pipe in the concrete. If that was not there I’d suggest breaking up the concrete using expansive concrete. Mix it up and pour in the hole and as dries and expands it will break up the concrete block. It’s probably not strong enough to break open that steel pipe though. It’s cool stuff, drill vertical holes in the concrete, pour the mix in and it will break it apart. It will break solid rock also. I used it after cutting a door way between my two basements after building an addition. I was left with a door sized slab of concrete on the floor and broke it up into manageable pieces that way.
I love my sawzall. I’ve lent it out a few times, but will remember to remind future borrowers to wear gloves when using it. I lent it to a friend who didn’t wear gloves and he ended up with some horrible blisters on his one hand. His wife is pissed off at me because of this. 
That’s your superpower, Bro
I wish I had a pole. Festivus pole, fireworks launcher, spooky Halloween prop (gallows, slenderman) support, condor nest base. Fun all year.
I once saw (!) some maintenance guys at a factory cut off anchor bolts in the floor. A sawzall with a longish thin metal blade and a skilled operator made a tough job look really easy. A concrete filled pipe will be more difficult.
I was unfamiliar with expansive concrete, so thanks for the new knowledge. It does seem to come with prerequisites: some money ($50 for 11 lbs of powder), and some serious drilling equipment to put deep 1-1/4” holes in stone/concrete.
Still, there that hunk of old concrete porch under my deck that mocks me anytime I replace deck joists. My brother-in-law has a demo-drill, so maybe someday I could have a bunch of movable chunks.
A rather large demo drill and wide core bits are needed for holes 2" wide or more. You can rent those from Home Depot and others. It’s noisy, dusty, and kinda fun too. It’s cool to come back and see the concrete cracked up like a broken mirror.
Nice thing about the grinder vs sawzall is the grinder doesn’t much care about hitting the concrete, whereas you can write off a sawzall blade in a hot second.
Quote from a friend (who concurs):
"I would like to point out that this is not a Milwaukee SawzSome. Nor is it a Milwaukee SawzMost. This is a Milwaukee SawzAll.
I love my grinder. It’s a Makita 4" which is sufficient but I’d suggest the more common 4-1/2" size. I have a larger grinder also, but this one sees a lot of work for cutting and grinding metal and masonry. When I’m welding I keep a wire cup on it for cleaning slag, it’s nice and light, easy to use with one hand. And it’s help for 30 years so far while many other cheap tools did not survive. Just sayin’ while were talkin’ ‘bout lovin’ tools.
I’ve got your expansive powder right here. It’s called dynamite 
Stranger
A strong wind would have taken that tree down. Not much use with concrete except to detonate a high explosive.
Detonation cord is a high explosive (typically PETN, RDX, or HMX) and a few turns will both fracture the steel pipe and shatter the filler concrete inside.
Stranger
Can’t say about that particular use. It’s often used to clean boilers, would seem to be too destructive for that purpose based on your assessment, however, I’m not familiar will different types of such cord and their use.
Applications
A large portion of MDC / MDF manufactured at PSEMC is loaded into higher assemblies and components used in multiple aircraft, missile, munition, space and commercial applications.
Detonating Explosive Transfer Lines (ETLs)
Aircraft, Missiles, Space & Oil/Gas
- Shield Mild Detonating Cord (SMDC)
- High Pressure Shielded Mild Detonating Cord (HP-SMDC)
- Flexible Confined Detonating Cord (FCDC)
- Confined Detonating Cord (CDC)
- Flexible Detonating Cord (FDC)
Expanding Tube Assembly (XTAs)
Aircraft, Missiles & Space
- Emergency Canopy Release Lines (ECRLs)
- Stage Separation Assembly
- Underwater Severance Assembly
- ETRS Ring
Canopy Fracturing Assemblies
Window Cutting Assemblies (WCAs)
Skin Severance Assemblies (SSA)
Gun Conical Charge Initiation Cord
Munition/Weapon Initiation
Stranger
I suggest buying a face shield at Harbor Freight.
Angle grinders are very useful tools. They do throw a lot debris. Go slow and don’t force the cut. You can break a disc and that’s another reason for a face shield.
It will easily cut pipe. A 15 minute job. Tool rental stores sometimes have angle grinders.
Great advice in general. I got hot in the face with rocks a few times while weed whacking. I started wearing protective glasses even though they were uncomfortable. I’ve replaced my glasses a few times when a rock shattered them.