I've always felt that zeds do way too much damage to blocks. There's no reason to not go for the reinforced concrete and steel, precisely because zeds are so damn destructive. If you're not constantly monitoring your constructions, one can carve tunnels into concrete. Concrete! At the very least, I would think their arms would break before getting much headway. Similarly for something like brick: yeah, if you get enough guys pounding on a brick wall, they can probably take it down without tools. Depending on the foundation, they could probably knock it over before they punch a hole into it.
Maybe the solution is make reinforced concrete and steel more expensive, luxury items, and in general, decrease the amount of damage zeds do to blocks. Then mid-grade materials are still viable and worth maintaining, rather than just the stop-gap. If you want to churn out massive quantities of concrete and steel, then be prepared to invest in forges and mixers (and all the heat they generate).