Magnesia refractory castables usually use sintered or fused magnesia as aggregate and powder, with particle size grades of 5-2.5mm33%, 2.5-1.2mm22%, 1.2-0.6mm25%, 0.6-0.15mm20%. The concentration of 30% sodium hexaphosphate solution is used as binder, high alumina cement as accelerator, iron scale or clay powder as sintering agent
The preparation process is to mix the refractory aggregate with two-thirds of the binder for about 3 minutes. After all the aggregate surfaces are wet, add the refractory powder and mix evenly. Finally, add the remaining binder, accelerator and sintering agent and continue mixing for about 5 minutes. After vibration molding, it shall be cured naturally for 3 days without watering. Sodium hexametaphosphate solution binder shall be used as little as possible to ensure the high temperature performance of the material
