Refractory castable is a new type of refractory material. Its formulation varies depending on the specific location of the industrial kiln to be lined. The grade, impurity content, and sintering quality of the refractory materials also affect the performance of the castable. So, what is alkali-resistant castable, and how is it classified? Let’s explore it below.

Alkali-resistant castable refers to a pourable refractory material that can resist corrosion by alkali metal oxides (such as K₂O and Na₂O) at medium and high temperatures. Its composition is similar to that of ordinary calcium aluminate cement-bonded castables, consisting of a mixture of alkali-resistant refractory aggregates, powders, binders, and admixtures. Based on different service conditions and environments, alkali-resistant castable is divided into lightweight alkali-resistant castable and heavy alkali-resistant castable. Those with a porosity greater than 45% are classified as lightweight alkali-resistant castable, while those with a porosity less than 45% are heavy alkali-resistant castable. Heavy alkali-resistant castable can be further divided into medium-temperature alkali-resistant castable and high-temperature alkali-resistant castable.

The aggregates used in lightweight alkali-resistant refractory castable include alkali-resistant ceramsite, clay-based porous clinker, waste porcelain, and high-strength expanded perlite, with calcium aluminate cement or sodium silicate as the binder.

Alkali-resistant materials can use high-silica refractory raw materials. At high temperatures, these materials react with alkali metal oxides to form a high-viscosity liquid phase, creating a dense glaze-like protective layer that prevents further penetration and corrosion by molten alkali metals. The aggregates for heavy alkali-resistant refractory castable include clay clinker and waste porcelain. The binder and alkali-resistant powders are the same as those used in lightweight alkali-resistant castable, with calcium aluminate cement generally serving as the binder.