Table salt is commonly used by stove builders for sealing and repair,
to improve the adhesion of mixtures and due to its relatively low melting point of about 801°C.
Usually it is mixed with clay, wood ash or both.
At higher temperatures the mixture may turn into ceramic.
crushed clay and wood ash in equal proportions;
a quarter of table salt;
water to make a stiff paste.
Recipe for fixing cast iron stoves:
You can seal cracks in a wood stove with this simple old-time homemade cement: Put a cupful of wood ashes in an old can, add about half a cup of salt, and slowly stir in enough water to make a stiff paste. Plaster the broken places in the metal with this mixture. Then build a fire and bake the sealer hard. Your repair job will last quite well if you don't bump the mended spots.
Source: Mother Earth News
Thanks for the explanation Karl. I'm very glad that you called, maybe telepathy still works. I highly value your knowledge and advice. For the test, I built a j-tube stove made of fireclay tiles, as a glue I used a paste of wooden ash and salt. After several hours of operation, the glue hardened really like a ceramic. I wonder if it's a chemical process or just the salt hardens and done. Karl please, could you add a link to Mother Earth News? Well thank you.