I made no such clarification, but repeated the same point I made from the beginning. I stated that “ANYTHING may be destroyed” in my FIRST response to you. Go back and read it.
Your initial claim is that concrete and rebar is better than steel alone. That is factually wrong, as it depends upon the use. If the argument were about sustaining a pure gravity load, as in a “skyscraper,” then you would be correct in your assertion. However, that is not the case with a wall structure - nor is it even practical from an engineering point of view. Treated steel is more than sufficient to effectively and economically accomplish the task of deterrence.
A steel structure may not be as aesthetically pleasing to the eye as would be concrete - but I don’t give a rat’s tail about aesthetics when it comes to spending my tax dollars - I want efficiency and effectiveness. As engineers are fond of saying: “keep it simple, stupid” And “get the mostest for the leastest!”
There is a kind of steel which oxidizes (rusts) to leave a coating which does not further deteriorate. The term Core 10 popped into my brain, but may not be it. Advantages to the steel wall. It is hard to sneak up behind it and plant explosives, or build a ramp, or raise a ladder without someone seeing. I suspect that visual surveillance could be set up at some distance to scan a fairly long section of fence regularly over time. Also, patrols driving along a fence could see what could not be seen driving along a wall. Of course terrorists are coming in from Canada, and by plane and boat, not from Mexico. I wouldn’t be surprised to find out that there was a bounty payable to coyotes to turn in Muslim terrorists. Also, I doubt that the drug cartels would appreciate the attention and they play even dirtier than the terrorists.