Roof Deck?

[TTRR11]

I'm working on a reroof project for a school & ran across an issue with the existing roof deck for one particular area.
Building was built in the 50's. Added on over the years several times.

Someone took roof cores & didnt take note of the materiality of this particular core.
I have some photos & some existing drawings that kind of talk about what the existing deck may be.

The person who took the core thinks it is insulation over lightweight insulating concrete over tectum...about 7.5" thick total.
Photos seem to suggest something different. There were other cores taken at other roofs & maybe there was some confusion.

Original 50's drawings say "Porex" (see images in link below)

Drawings from a reroof project from a few years ago (2005), supposedly took a core & said that it is "dense poured gypsum"

Photos & Images:

https://www.dropbox.com/sh/2brhj7zqlkvhe64/AAAC7ijSGe2aO0SEfzHBPAw0a?dl=0

The core photos are two of the same.
Underside photos show clearly a tectum deck, but the adjacent area is below where the roof-top core was taken.
It has a smooth surface that doesnt suggest LWC on a tectum deck.

Any idea of what this deck might be?
Any help would be greatly appreciated.

Thanks

 

[JAE]

Based on your Dropbox link I'd think that this is a tectum type sheathing on bulb tees with a poured LW concrete or insulating concrete topping.

The one detail says "Precast" but that might be an architect's uncertain terminology.

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