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In a First, America Dropped 30,000-Pound Bunker-Busters—But Iran’s Concrete May Be Unbreakable, Scientists Say (www.popularmechanics.com)
submitted 1 year ago by to c/technology@lemmy.world
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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.”

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[–] 1 point 1 year ago

There was a "etch your VIN in your car window glass" campaign around here years back, they had a liquid solution of HF that they were wiping across printed stencils to do the glass etching. The fact that its natural state is a gas just makes it all the nastier to handle - and possibly even more effective at diffusing through the cracks to cause hydrogen embrittlement of any steel reinforcement it may come into contact with.

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