Low Cement Refractory Castable

Low cement castable is made of CA-70 cement as a binder, mixed with refractory aggregate and powder or admixture in proportion, and then mixed with water, formed and cured. It is characterized by fast hardening, high strength, low price, easy to obtain and convenient construction. When aluminum silicate materials are used to prepare refractory castables, it has a certain ability to resist sulfate erosion. The use temperature of this castable is about 1400℃. In the past, CA-70 cement refractory castable was widely used in thermal equipment such as steel rolling heating furnaces, which can realize mechanized furnace construction and have a long service life; now, this low cement castable is mainly used in kilns such as heating furnaces, boilers and petrochemical industrial furnaces, and is also used in metallurgical systems and low-temperature thermal equipment, and has achieved good results.

Low cement castable has the characteristics of fast hardening and high strength. After molding and standard curing, it has high compressive strength. This is because the hydration heat released by the high content of CA in cement promotes the rapid hydration reaction of CA2.

 

The maximum use temperature of low cement castable is about 1500℃, which can meet the use requirements of general industrial kilns. After 1200℃, due to the continuous increase in the amount of liquid phase, sintering has occurred, and the castable forms a ceramic bond, so the strength increases with the increase of heating temperature; the load softening temperature and refractoriness are high. Low cement castable is a relatively good furnace building material.

Main physical and chemical indicators of low cement castable (I)

The main mineral phase of low-cement refractory castables is CA2. Compared with CA-50 cement, it is characterized by slow hydration speed, high strength in the later stage and high refractoriness. Therefore, when CA-70 cement is used to prepare refractory castables and cured under normal temperature and humid conditions, it also shows low early strength and high strength in the later stage. If it is cured at a higher temperature or with steam, it can also achieve the effect of fast hardening and high strength. In addition, due to the high content of CA2, more aluminum gel is formed after hydration, so more active alumina is produced after heating and new minerals are formed, which is beneficial to improve the performance of refractory castables.

Low-cement refractory castables are mainly used in high-temperature areas, so alumina clinker with high Al2O3 content is often used as refractory aggregate and powder, and materials such as corundum, mullite and chromium slag can also be used. The critical particle size of refractory aggregate can be 15mm or 10mm, depending on the thickness of the lining. In order to improve its construction performance and high-temperature performance, admixtures should be used.

After the low cement refractory castable is formed and initially set, two methods can be used for curing: standard curing and steam curing. Different curing methods have different room temperature compressive strength.

The refractoriness of low cement refractory castable is relatively high, generally around 1790℃; due to its high strength, it also has good wear resistance.

Main physical and chemical indicators of low cement castable (II)

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