Is limestone combustible

Answer 1

According to Wikipedia,limestone begins to break down into Calcium Oxide (CaO3; quicklime, mixed with water to create lime mortar) and Carbon Dioxide (CO2) at 825oC/1517oF. Another source (?) says it's 840oC/1544oF. The article at http://www.docbrown.info/page01/ExIndChem/ExIndChem.htm says heating limestone in a kiln at over 900oC/1652oF will cause it to break down into CaO3 and CO2.

To be on the safe side, I'd go with the lowest temperature, 825oC/1517oF, or even 800oC/1472oF.

Typical temperatures inside a metal wood stove will be 204-438oC/400-1000oFor more, but they can be higher (leading to better combustion) in the firebox of a masonry heater, whose walls absorb heat slowly enough to allow the buildup of much higher temperatures. I imagine limestone is a very bad idea for the walls of the firebox itself!

Typical temperatures in a house fire are at least 593oC/1100oF according to several sources, but I would imagine they are probably less than the 800oC/1472oF safety margin for a typical residential house fire.

For structural or mass-heating applications (e.g. masonry stove exterior), be sure to research the appropriate mortar, taking into account mortar strength relative to the limestone (should be less to avoid cracking of the stone itself due to expansion/contraction) as well as thermal properties.

I cannot guarantee my sources, but this should at least give you some idea of what to expect. I'll come back and update this article when I get the time to do some more serious research.

Interesting, if only slightly relevant:

- Fired adobe houses (built, then fired) (best known through the writings of Nader Khalili)

- Masonry heaters, Russian fireplaces, kachelofens, etc.

- Effects of acid rain on various types of stone - very severe in limestone

Answer 2

No. Limestone is not combustible in any way.