Introduction of Refractory Castable
Structure and Type of Refractory Castable.
Refractory castable is a mixture composed of refractory aggregate, powder and binder. After adding water or other liquids, it is suitable for pouring and vibration construction. It can also be made into prefabricated parts with specified shape and size in advance to build 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, if an appropriate amount of stainless steel fiber is added to the refractory castable used in the parts with large mechanical force or strong thermal impact, the toughness of the material will be significantly increased. If inorganic fiber is added into the heat insulation and refractory castable, it can not only enhance the toughness, but also help to improve its heat insulation performance. Because the basic material composition (such as aggregate and powder, admixture, binder and admixture), setting and hardening process and construction method of refractory castable are similar to those of concrete in civil engineering, it was also called refractory concrete.
Refractory castable has the advantages of simple production process, labor saving and energy saving, high construction efficiency and good quality. Materials with excellent performance can be prepared or selected on site according to needs. Therefore, refractory castable is an amorphous refractory with large dosage and wide application range in furnace building engineering.
Structure of Refractory Castable
Refractory castable is composed of binder, aggregate and admixture, and sometimes accelerator is added.
Refractory aggregate is the main body of refractory concrete. Various refractory materials (clay, high alumina, silica, magnesium, etc.), calcined clinker or various waste bricks can be used as refractory aggregate when broken to a certain extent. The particle size of aggregate has a great impact on the quality of products. Therefore, in addition to certain restrictions on the particle size of aggregate, there are also certain proportion requirements in quantity. The refractory aggregate is equivalent to the gravel and sand of ordinary building concrete. In the batching of refractory concrete, aggregate generally accounts for 70% ~ 80%. Among them, coarse aggregate (5 ~ 20mm) accounts for 35% ~ 45% in batching; Fine aggregate (0.15 ~ 5mm) accounts for 30% ~ 35%.
The cementitious material plays the role of cementation and hardening, so that the product has a certain strength. Cementitious materials include ordinary portland cement, bauxite cement (high sales Cement), magnesium cement, sodium silicate, phosphoric acid, etc. In order to ensure that the concrete has sufficient fire resistance (the more the amount of cement is the flux at high temperature, the lower the fire resistance of the concrete), and to reduce the volume shrinkage during use, the amount of cement should be as small as possible, generally 10% ~ 25%, and it is hoped that cement and bone can not produce more low melt.
Some refractory concrete (such as phosphate refractory concrete) must also add a small amount of accelerator in the batching to accelerate the hardening and consolidation of concrete.
In order to improve the performance of refractory concrete, such as increasing the strength in the process of heating up and reducing the volume shrinkage, 10% ~ 25% admixture is often added. The raw material of the admixture is the same as that of the aggregate. It is finely ground refractory clinker powder, of which 70% ~ 80% fineness is less than 0.088mm.
Classification of Refractory Castable
Refractory castables are usually classified according to the size of porosity, selected binder or combination mode, type of aggregate and construction mode.
1. According to porosity, it can be divided into dense refractory castable and thermal insulation refractory castable;
2. According to the classification of cementation mode, refractory castables can be divided into four types: hydrated bonded refractory castables, chemically bonded (including polymerization bonded) refractory castables, hydrated and polymerized refractory castables (typically low cement bonded refractory castables) and agglomerated bonded refractory castables.
3. According to the special functions of binders and some materials, they can be divided into the following 7 categories:
(1) Clay bonded refractory castable;
(2) Ultra fine powder (such as silica fume) combined with refractory castable;
(3) Cement bonded refractory castable;
(4) Chemically bonded refractory castable;
(5) ρ- Al2O3 (hydrated Al2O3) bonded refractory castable;
(6) Low cement bonded 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 subdivided into non alkaline refractory castables and alkaline refractory castables.
5. According to the construction method, the refractory castable (body) can be divided into vibration construction refractory castable and self flowing refractory castable.
6. According to whether the refractory castables contain cement or CaO content, they can be simply divided into four categories: ordinary refractory castables, low cement refractory castables, ultra-low cement refractory castables and cementless refractory castables.