Needed a few lengths of concrete beam for another firewood store, but nothing in the right length in my pile.
So I had to cut one of the longer ones. This took some figuring. Initially I thought the answer was the big jangle grinder with masonry disc, but that is most definitely not the answer.
The right answer was chiseling through the concrete until the rebar is accessible. Then cutting that.
But! Cutting rebar under load is dangerous. The solution I came up with is to cut it 90% through and then stop and smash it with a hammer or pickaxe until it goes ping.
Much safer than it pinching the cutting wheel and flinging it at your face or ripping the grinder out of your hands.