For concrete to have strength it requires both reinforcement and thickness. The reinforcement needs to have a couple inches of cover concrete to properly imbed it for protection of the steel and to provide the hinge strength to put the steel in tension in the event of stress or strain. Just putting a couple of inches up is going to just cost you volume, as it is neither thick enough to imbed the steel, or to provide any strength. Typical concrete walls will be 6 to 8 inches thick.
Zone 7 A/B
Keep your words sweet. You never know when you may have to eat them.
Richard