Alkali resistant refractory castable is a mixture of refractory aggregate, powder and binder. After adding water or other liquid, it is suitable for pouring and vibrating construction. It can also be made into prefabricated parts with specified shape and size in advance for building industrial furnace lining. In order to improve the physical and chemical properties and construction performance of refractory castables, appropriate additives such as plasticizer, dispersant, coagulant, retarder, expansive agent, degelling agent and gel agent are often added. In addition, the toughness of the castable used in the place with large mechanical force or strong thermal impact will be increased significantly if a proper amount of stainless steel fiber is added. If inorganic fiber is added to the insulating refractory castable, it can not only enhance its toughness, but also improve its thermal insulation performance. Because the basic material composition of refractory castable (such as aggregate and powder, admixture, binder and admixture), setting and hardening process, construction method, etc., are similar to the concrete in civil engineering, it was also called refractory concrete.

The production process of alkali resistant refractory castable is simple, energy-saving, high construction efficiency and good quality, and the material with excellent performance can be prepared or selected on site according to the needs. Therefore, the refractory castable is a kind of amorphous refractory which is widely used in furnace construction.
Alkali resistant refractory castable is composed of cementitious material, aggregate and admixture, and sometimes coagulant is added.

Refractory aggregate is the main body of refractory concrete. All kinds of refractory materials (clay, high alumina, silica, magnesia, etc.) can be used as refractory aggregate after calcination of clinker or crushing of various waste bricks to a certain extent. The particle size of aggregate has a great influence on the quality of products, so there is a certain limit to the particle size of aggregate, and there is a certain proportion requirement in quantity. The refractory aggregate is equivalent to the gravel and sand of ordinary building concrete. In the proportion of refractory concrete, aggregate generally accounts for 70% - 80%. Among them, coarse aggregate (5-20 mm) accounts for 35% - 45% of the ingredients; fine aggregate (0.15-5 mm) accounts for 30% - 35%.

Cementitious material plays a role of cementation and hardening, so that the products have a certain strength. Can be used as cement: Ordinary portland cement, alumina cement (high sales Cement), magnesium cement, water glass, phosphoric acid, etc. In order to ensure that the concrete has enough fire resistance (the binder is the flux at high temperature, the more the quantity, the lower the fire resistance of the concrete), and to reduce the volume shrinkage in the use process, the amount of the binder should be as small as possible, generally 10% - 25%, and it is hoped that the binder and the bone material can not generate more low melting materials.

Some refractory concrete (such as phosphate refractory concrete) also need to add a small amount of accelerator in the batching to accelerate the hardening and consolidation of concrete.

In order to improve the performance of fire-resistant concrete, such as increasing the strength in the process of temperature rise and reducing the volume shrinkage, 10% - 25% admixture is often added. The raw material of the admixture is the same as the aggregate, which is the finely ground refractory clinker powder, of which 70% - 80% fineness is below 0.088mm.
Refractory castables are usually classified according to the size of porosity, selected binder or bonding method, type of aggregate and construction method.

1. According to porosity, it can be divided into dense refractory castable and heat insulation refractory castable;

2. According to the classification of cementation methods, refractory castables can be divided into four types: hydration combined refractory castables, chemical combined refractory castables (including polymerization combined refractory castables), hydration combined refractory castables (typical representative is low cement combined refractory castables) and agglomeration combined refractory castables.

3. According to the special functions of binders and some materials, they can be divided into the following 7 categories:

(1) Clay combined refractory castable;

(2) Superfine powder (such as silica fume) combined with refractory castable;

(3) Cement combined refractory castable;

(4) Chemical bonded refractory castable;

(5) ρ - Al2O3 (hydrated Al2O3) combined with refractory castable;

(6) Low cement combined refractory castable;

(7) silicon and aluminum sol (sol gel) combined with refractory castables.

4. According to the combination of raw materials, refractory castables can be divided into oxide refractory castables, non oxide refractory castables and composite refractory castables. Oxide refractory castables can be divided into non basic refractory castables and basic refractory castables.

5. According to the construction method, the refractory castables (bodies) can be divided into two categories: vibration type and self flow type.

6. According to whether the refractory castable contains cement component or CaO content, it can be simply divided into ordinary refractory castable, low cement refractory castable, ultra-low cement refractory castable and no cement
Refractory castables mainly include ordinary quality, light weight, low cement, ultra-low cement and other products. According to their different characteristics, they are used for:

A: Blast furnace hot air system, refining device outside the furnace, lifting pipe lining, pretreatment of molten iron, Lance for oxygen and argon blowing of molten steel.

B: Steel making and rolling system, electric furnace top, electric hole triangle area, steel barrel, heating furnace, soaking pit, inner lining of heat treatment furnace, prefabricated block of water-cooled slide rail, burner of blowing port and fire stop port.

C: Cement rotary kiln, cooling cylinder lining, floating glass tank top and bottom lining, petroleum cracking reactor, high temperature wear-resistant lining, high temperature lining in ammonia plant and gas furnace, etc.