Any suggestion for a non-combustible polymeric or inorganic etc. adhesive with high temperature resistancy (500 or 600 deg), with mechanical properties at structural level?
You could try silicone(polysiloxane) , altough you should be careful about the medium of your test. Silicone is solouble in som non-polar liquids, for instance tolouen.
there are some commercial products that intended for gluing and masking fractures and immediate repairs of metal or ceramic materials working in temperatures up to 1200° C. Excellent for repairing car silencers, exhaust pipes and for sealing exhaust conduits from fireplaces and furnaces. Resistant to flames and combustion gases and some chemicals.
You can find at: https://chemistik.eu/en/products/household-adhesives/