polypropylene fibres for use in home brew castable

[jersey bob souvlaki]

Hi. I saw two things recommended for reinforcing home brew castable - stainless steel needles and polypropylene fibres. Looks like i'm not going to be able to find the needles but I found these fibres:https://www.isomat.gr/wp-content/upl...ENE-FIBERS.pdf
Would anyone like to comment on their usefullness for making the inner dome of a cast oven, please? thanks, bob.

[Toomulla]

The terms needles and fibres are used interchangeably. SS will provide some long term reinforcement polypropylene will not.

[david s]

The correct term for the ss needles is "melt extract fibres", but commonly called needles.
The polypropelene fibres provide good compressive strength in standard concrete but lousy flexural strength. In castable refractory they melt at 160C and provide a network of tiny pipes to assist in water removal. Because they are so fine the density and strength of the casting is not affected. Approx 1:500 by volume is required, as they are so fine, but even dispersal is essential which requires about double the amount of normal mixing.

[jersey bob souvlaki]

I misspoke when I talked about reinforcing with the polypropylene. david s had said that "proprietary castables contain fibres that burn away at low temp leaving tiny pipes that water can escape through to prevent blowing." What I meant about the polypropylene was that it would improve the home brew mixture and help in preventing one type of problem.
Also, I've searched and haven't found anyone mention a suitable substitute for the stainless steel needles.

[jersey bob souvlaki]

Thanks for the responses. David replied as I was typing my correction. I was wondering if those particular polypropelene fibres looked good for that purpose.

[cnegrelli]

I paid about $10 per pound for the SS needles here in Denver. On a 32 in oven, using 2% by weight, that's 6.5 lbs, or $65.

The thought of a slumping, crumbling build made that an easy decision. I mixed up the castable first to desired consistency with last part done with hands. Then I added sprinkles of SS needles and worked that hard with a hoe.