I have had to break up a large area of fairly thick dense concrete slab- which I knew was overlying some huge old stone slabs which I didn’t want to damage. A gentle approach required! The technique I used was based on stitch drilling, similar to how they split rock off a face in a quarry. Believe it or not, it only took quite mild taps with the 12lb sledge on those two stubby chisels each time, turn and turn about, for the crack to open along the line of weakness created by those holes, which I pitched at about 2 inches. Note the tell-tale “bite marks” along all the worked edges. A most satisfying technique.
