One of these with an 18" blade will go all the way through way faster than a little Sawzall.
The TS 800 STIHL Cutquik® cut-off machine features a magnesium guard making the machine a full 0.7 pounds lighter than the previous model. The TS 800 features a 16” cutting wheel, the largest size we offer in a handheld design. It’s also fuel efficient, with enough power to
cut through asphalt, concrete, rebar, iron, and steel with ease.
The wall has 6" bollards and the 16" blade only does 5.6" so take the blade guard off and it will take an 18" blade no prob. Don't even need electricity.