ammonium nitrate won't burn on it's own, it's an oxidizer
McVeigh used ammonium nitrate and diesel in 55 gal barrels i believe , detonated by dynamite
The dynamite gives a sharp jolt to the fuel and nitrate causing the nitrate to release massive amounts of oxygen. Hence a fuel air explosive
In Beirut that building could have burned to the ground on the ammonium nitrate and it would have simply melted.
i know that
impossible
i've use blow torches on ammonium nitrate – I even set a pot over direct fire to melt it
While we're on the subject, take a plastic coke bottle and fill it half full of ammonium nitrate then almost full of water and shake it. Does anyone know what you get?