An aerated refractory is provided comprising a mixture containing a phosphate compound, a metal oxide, a calcium containing compound; and an agent for increasing the volume of the mixture. Also provided is a method for protecting a substrate with aerated refractory, the method comprising dry mixing mono-potassium phosphate with a metal oxide and a calcium containing compound (i.e. hydroxyapatite) to produce a homogenous dry mixture; adding water to the mixture to produce a slurry; adding a foaming agent to the slurry; applying the slurry to the substrate; and allowing the slurry to dry.