Temperature differences in material, heat expansion and contraction shrinkage of edges with cooling downwards. I have seen a couple that use portland cement and perlite that people say work well, but others say not to use those because it will cause cracking and crumbling. The first three components are mixed together thoroughly. Refractory concrete mixture ingredients recipe for mixing by hand and concrete in building pizza ovens. ... Measure out the perlite and add it to the mixing tub. mix stuff. I used a 1-gallon bucket to measure the parts. You should see no trace of the kaowool in the mix. Mixing high temp refractory - adding perlite? This is a really good formula for insulating refractory cement made from materials you can get anywhere. The concrete or screed should be laid, levelled and then covered with a polythene membrane and allowed to cure for at least 18 hours. ... Perlite and furnace cement refractories are OK for melting aluminium, but the perlite starts to break down around the brass temperature mark. The refractory mix is composed of Portland cement (1.5 parts), silica sand (2 parts), perlite (1.5 parts) and fireclay (2 parts). high-temp furnace cement + perlite (4:1 ratio) is a recipe for refractory cement (i think) i plan on using that mix (unless someone tells me not to?) This Pure Cement - no rocks or sand) 2 parts silica sand (The same stuff you use for your GreenSand) 1.5 parts perlite (Pure - not a blend of other things meant for plants. Internal lining boards attached to prevent mixing material abrasion on drum, replaceable high wear resistance liners could continue to be used, low maintenance cost and long service life. Mix it completely until there is no dry perlite. (that stuff is nasty to breathe) Add the clay mix to the mixing tub. If you've not found your way there, alloyavenue.com has any amount of info on DIY metal casting. There are much more outstanding features mixing refractory cement with perlite machine than common concrete mixer, Both the mixing speed and homogeneity are very high. "NOT" Vermiculite either!) Best DIY refractory cement recipe Best DIY refractory cement recipe. Heat differences in materials. How to make heat resistant concrete type for buildig wood fired pizza ovens and similar applications where heat and heating is present.