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Analysis of the reasons for the performance decline of refractory castable
A series of performances decline for the refractory castable are due to:
1. In order to completely hydrate the cement,excessive addition of water (10%~15%) during stirring results in high apparent porosity and low density of ceramic refractory castable.
2. The calcium aluminate hydrate has strong dehydration and recrystallization effects in the middle temperature stage, which destroys the microstructure of the hard spots in the castable, and makes the strength of the refractory castable drops sharply in the middle temperature stage.
3. The cementitious binder will bring more calcium into the castable, resulting in a decrease for the refractoriness under load and a deterioration of the thermal shock resistance index of the ceramified refractory castable . In view of the problem of poor high temperature performance of ordinary refractory castable, low cement castable refractory effectively avoid the regret of high temperature performance. The so-called low-cement castable refractory have a cement content of less than 8%, while less than 4% are called ultra-low cement refractory castable.
In contrast, the deficiencies described above for conventional refractory castable translate into the advantages of low cement refractory castable.Its structure is dense.It has a low apparent porosity, high refractoriness and refractoriness under load, high temperature strength, and good thermal shock resistance.However, due to its low cement content, the condensation time is so long, the early strength is low, that it is particularly unfavorable in winter and low temperature conditions for construction. Therefore, we should pay full attention when laying bricks.