I am using a 750 mm x 750 mm x 200 mm slab with 12 mm rebar placed at every 150 mm. I am bit confused about how I can create an anode and cathode for this slab? And I am using impressed current as a corrosion acceleration method.
I believe your slabs are in aqueous environment. Make electrodes (Pb ally, Pb_In alloy. Platinized titanium etc.) and fix on concrete via neoprene rubber gasket to isolate environment and the connection. Now you can apply voltageas required. Current density has to be checked and fixed for perfect protection
I like to add, Impressed current is the amount of electricity/potential needed for transforming corroding surface from anode to cathode or to cathodic potential zone. Electrolyte must be there. Autocontrol unit allows the current to pass as required for maintaing the substrate in cathodic potential zone.