Previously, a yield strength of 5,000 pounds per square inch (psi) was enough for concrete to be rated as “high strength,” with the best going up to 10,000 psi. The new UHPC can withstand 40,000 psi or more.
The greater strength is achieved by turning concrete into a composite material with the addition of steel or other fibers. These fibers hold the concrete together and prevent cracks from spreading throughout it, negating the brittleness. “Instead of getting a few large cracks in a concrete panel, you get lots of smaller cracks,” says Barnett. “The fibers give it more fracture energy.”
The reality is that “tactical” and “strategic” are functionally meaningless adjectives when applied to weapons or systems.
Theoretically, “tactical” refers to how a military unit engages another military unit. It is how a commander wins a battle against an enemy unit.
“Strategic” refers to how a nation engages another nation. It is how a government wins a war.
The term “tactical nuke” referred to something that a lower level commander could have been authorized to use under his own judgment. If Soviet tanks were rolling across Europe during the cold war, commanders may have been granted the discretion to use small nuclear weapons to halt their advance.
Since the the doctrine of Mutually Assured Destruction was established, there has been no such thing as a “tactical” nuke. Any wartime use of a nuclear weapon of any kind demands an escalation to total annihilation. I used the term “tactical” ironically, to refer to a pre-“MAD” doctrine that can no longer exist.
In declaring that conventional bombs cannot penetrate this fixed bunker, it seems that someone is pushing for unconventional warfare. The reality is that this bunker is not impenetrable. It shares the same weakness as any bunker: getting into and out of it. Bomb the entrances to the bunker, and it will take months or years to tunnel back in. Whatever they are doing inside it, they won’t be doing until they manage to dig it up again.