Refractory cement is a powerful and quick-setting binder, also known as high alumina cement. The written language is called aluminate cement. It has a wide range of uses and applications. According to the brand and material, it is divided into: calcium aluminate cement, barium aluminate cement and barium zirconium aluminate cement. It is also used as a binder or admixture for amorphous refractories.
Refractory cement is a good binder or admixture for unshaped refractory castables, and it is also used more. It should be pointed out that the aluminate cement national standard GB/T 201-2015 stipulates that its code is CA, and it is divided into four categories according to the percentage of AL2O3 content: CA-50, 50%≤AL2O3＜60%: CA-60, 60%≤ AL2O3 <68%: CA-70, 68%≤AL2O3 <77% and CA-80, 77%≤AL2O3. Referred to as CA-50 cement, and so on. The total sulfur and chlorine contents are both ≤0.1%.
Fineness of refractory cement: the specific surface area is not less than 300㎡/Kg or 0.045mm, and the sieve residue is not more than 20%. The initial setting time of CA-60 cement shall not be earlier than 60min, and the other grades shall not be earlier than 30min; the final setting time of CA-60 cement shall not be later than 18h, and the other grades shall not be later than 6h. The main mineral composition of CA-50 cement is CA, which belongs to fast-hardening and early-strength cement, and its refractoriness is ≥1460℃.
The variety of refractory castables produced by refractory cement (Zhengzhou Hongtai Refractory Co., Ltd.) as a binder is relatively low. The mix ratio is different, the performance is different, the construction method and maintenance system are also different, but the factors affecting the performance are basically similar the same. Cement is one of the important components of refractory castables. It is an important material that determines strength and also affects other properties. Different types and amounts of cement have different effects on performance.
For example, the cement dosage of CA-50 cement high alumina refractory castable has obvious influence on its performance. The refractory aggregate and powder are both secondary bauxite clinker, the ratio of aggregate to powder and cement is 70:30, and the amount of water added is 10%. With the increase of cement dosage, the compressive strength at room temperature increases. When the compressive strength after burning at 1200 °C is 40%~65% lower than the drying compressive strength, the refractoriness and softening temperature under load continue to decrease, and the linear shrinkage after burning also increases with the of increase. This is due to the high impurity content and low refractoriness of CA-50 cement. When the dosage increases, the amount of liquid phase in the castable heating process is large, resulting in a decrease in performance. Therefore, under the condition of ensuring the strength at room temperature, the amount of CA-50 cement should be reduced as much as possible to improve the high temperature performance of the refractory castable. When the amount of cement is reduced, the refractory powder should be appropriately increased, so that the combined amount of cement and powder can fully wrap the refractory aggregate, and the refractory castable can obtain the maximum compactness. Commonly used cement dosage is 10%~12%
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