Cured concrete is slightly conductive, in the millions of ohm range for a small spot. But if you were to wet a large area, then you are making contact over a large number of "points", each of whgich is slightly conductive, but altogether those millions of tiny points have a low enough resistance to allow current levels high enough to kill youif they go through your heart. Ir, you may just fall down and hit your head and knock yourself silly.