How to mix refractory castable with low cement reasonably and scientifically?（2）

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How to mix refractory castable with low cement reasonably and scientifically

(3) Binder for low cement castables
There are many types of binders used in low-cement castables, from early water glass, soft clay to current resins, fine powder sol, etc., the bonding system has changed a lot, but aluminate cement is still the safest to use. The most stable quality and the most widely used binder. According to the provisions of GB202000 "Aluminate Cement", calcium aluminate cement has four varieties of CA-50, CA-60, CA-70 and CA-80, and its main mineral composition is monocalcium aluminate (CA) and dialuminate Monocalcium (CA2), calcium dodecahydrate heptaaluminate (C12A7).

Calcium aluminate cement generally contains CA, CA2, C12A7, different mineral composition, different hydration temperature, and different hydration products. Studies have confirmed that calcium aluminate cement hydrates to form CAH10 and C2AH8, both of which are metastable hydrates, which will be converted to stable hydrates C3AH6. Due to this characteristic, the castable made of aluminate cement will decrease in strength with time and temperature changes. However, under the action of active SiO2 micropowder, the hydration process of calcium aluminate cement can avoid the formation of C2AH8, and directly generate calcite C2ASH8 to improve the normal temperature strength of the castable.

(4) Water reducing agent for low cement castable

Water-reducing agent is a kind of compound that can significantly reduce the water consumption of mixing when it is added to dry materials and mixed with water to keep the flow value of low cement castables basically unchanged, so it is also called water-reducing agent.

Water reducing agents are divided into two categories: inorganic water reducing agents and organic water reducing agents. Inorganic water-reducing agents are mainly electrolyte compounds, which can dissociate cations and anions in water and have conductivity. The inorganic water-reducing agents used as refractory castables mainly include sodium pyrophosphate, sodium polyphosphate, sodium polyphosphate, superpolyphosphate, sodium silicate, sodium carbonate, etc. The most widely used refractory castables are sodium hexametaphosphate and sodium tripolyphosphate.

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