A use for swarf chips

[Frank S]

I seem to remember that's exactly what vault building companies do to make the pre-fab panels,
adding swarf to the pretty dry concrete mix, vibrating the molds for hours.
I did a fast check and that's about what I found.

Thus purportedly getting more 10 times more ruggedness from today's 3" panel than the old 18" conventional concrete pour.
Then as an added benefit - the swarf probably also diverting the heat from a villain's torch -
making the wall "impossible to cut".
What they actually add to the mix is shrouded in the mystery of "proprietary info", of course...

-So, what swarf are they actually using?
Stainless for ruggedness? Aluminum for heat conductivity? "Tungsten swarf", if even existant, for the highest melting point?

Link: How bank vault is made - material, history, used, parts, product, industry, History, Raw Materials, Design

a long time ago I made a gun vault for a friend of mine out of 3/8" thick steel and lined it with 2 1/2" of concrete the door had a 7 bolt lock system but the real clincher was as I poured the concrete in the door I added crushed carbide cutters and ball bearings in the area where the combination lock mounted and swarf throughout the pours of sides of the entire vault The hinges were concealed inside of the box as opposed to the way most vaults are made then the interior was finished by another friend with 1" thick cedar finished inside dimensions were 72" tall 24" wide and 18" deep making it 80' x 32'x26" outside all dimensions approximate I have no idea how much it weighed but I would guess well over a ton. I told him when we set the combination to make dang sure it was something that he could never forget because a lock smith who would normally know where to drill into the door near the combination lock would never be able to drill the hole. the only way into that safe would have been to completely destroy it by cutting it up. He owned 3 guns that required the federal tax stamp to own one of them worth well over half a million dollars in 1998 money or so he said I never saw them.
I probably still have some of the drawings I made while designing the hinge and lock system somewhere on one of my hard drives