Locating the right Refractory mortar suppliers for your growing business Refractory mortar is simply a type of clay that can withstand high temperatures. Usually, it is made by mixing cement and fireclay, other ingredients like sand and some compounds like calcium aluminate are used to make it highly heat resistant. It is very useful for building structures that will be exposed to high temperatures like furnaces. International Ceramics is one such reliable brand that has pioneered this art with perfection.