Shawn is correct, it's been called ABC now for probably 20 years. No, I don't know what it stands for! Sometimes, material name depends on the Quarry. Today I hauled "3/4 ROC". A New name to me! It's "Non Spec" ABC. It's always been "Process Pit", to me & Most Quarry's. But the PP shows a lot of dirt in it, while This Non Spec seems to just be 3/4 rock & fines.
You can also get the same grades in re-cycled concrete. It's all up to it's Use, & what someone is willing [or not] to pay for. If it's to be Inspected, That's a different Story. As for the pipe, metal or plastic corrugated, If installed Correctly, it's as strong as concrete pipe. Just like an egg, or round object, if there is equal pressure on all sides, it's Very hard to crush! I'm sure I have driven over such pipes, & bridges, where I Didn't know what was under me. Troy, your's looks sufficient, but If I knew about it, I'd advise the Owner that he is Responsible, & maybe have it in writing. I see no problem in the rebar & concrete, other than "is it necessary"? One other question, would be, How Long will the present pipe Last? You do Mega rebar/concrete structure on top & sides, & say the pipe rots out in 10 years. I don't know. To put That much into it, you might want to start with a Concrete pipe. Wider, larger, & flared ends. Just some thoughts!