Brief analysis of main factors affecting bleeding of refractory castables

The bleeding of the refractory castable is related to many factors, such as the choice of raw materials, particle gradation, construction process, and the setting and hardening time of the material. The speed of the particles is directly proportional to the square of the size of the particles, proportional to the density difference between the particles and the castable, and inversely proportional to the viscosity of the castable. Therefore, the larger the particle size of the particles, the worse the secretion of the castable, and the The greater the density difference of the castable, the more severe the bleeding, and the smaller the viscosity of the castable, the easier it is for bleeding.

 

① The effect of vibration on bleeding. During the construction process, the castable is in a fluidized state. At this time, the free water in the castable is easily overflowed under the pressure. Therefore, the vibration time should be controlled reasonably, until the slurry on the surface of the castable and most of the gas are discharged. Avoid prolonged vibration to avoid bleeding.

② The effect of coagulation and hardening time on bleeding. Bleeding of refractory castables usually appears within 30 minutes after molding is completed, but there is also a phenomenon of bleeding after 60 minutes or even 90 minutes after molding is completed. The reason is related to the admixture used in the material. The commonly used admixtures for castables are dispersants, coagulants and coagulants, dispersants with retarding properties, and dispersants with accelerating properties, either individually or in combination.
 

No matter how you add it, you first need to ensure that it has a dispersed water reduction effect. For the former, which shows bleeding in 30 minutes, in addition to the particle gradation, it is also related to the choice of dispersant. The effect of the dispersant is poor, and the slurry stays in a floating state for a short time, causing the particles to sink and bleed For the latter, the most important thing is related to the selection of coagulant. The coagulation is too slow, which causes the particles to sink and bleed.
 

Therefore, under the premise of ensuring application, the bleeding phenomenon of the castable can be effectively controlled by controlling the setting time.