What are the main factors for the poor flow properties of self-flowing refractory castables?

Artesian refractory castables, as can be seen from the name, fluidity is one of the most important properties, and the factors that determine its fluidity are mainly as follows:

1. Add water. Artesian castables are particularly sensitive to water addition, insufficient water addition, artesian value is too small, materials cannot flow normally to fill in the blanks, bubbles cannot be discharged; If the amount of water added is too large, it will cause the aggregate to sink, resulting in the separation of the aggregate from the matrix, and too much moisture will damage the density and strength of the material, as well as erosion resistance and wear resistance, etc.

2. Particle gradation. Raw materials: (1) aggregate: special grade bauxite (2) powder: special grade bauxite powder, pure calcium aluminate cement, a-Al₂O₃ micro powder. The fluidity of the artesian material comes from the cement slurry, < the 1mm part is more mud, the fluidity is good, and too much powder requires a large amount of water, so it is advantageous to increase the particle composition of 1~0mm. Particle size composition range with good fluidity: >1mm35-50%, 1~0mm15~30%, less than 0.088mm35~50%.

3. Coarse particle gradation and critical particle size. In the case of grading: >1mm 40%, 1~0mm 20%, < 0.088mm 40%, the coarse particle amount is large, the fluidity is good. Theoretically, the larger the particles in the > 1mm component, the smaller the contact area with the mud, and the smaller the flow resistance, the fluidity is good.

4. The influence of cement. With the increase of cement consumption, the self-flow rate increases the water demand, the fluidity becomes poor, and it is not conducive to the high temperature strength. On the other hand, the amount of cement is too small, and the temperature intensity is low, so the amount of cement added should be 5%.

5. The influence of white mud. The addition of white mud instead of part of the special grade bauxite powder is beneficial to the fluidity, the material of the clay is not too sticky, and the fluidity is improved quickly, the white mud is used as an auxiliary binder, the drying strength and the strength after burning at 1000 °C are significantly improved, and at high temperature, white mud helps the production of mullite and improves the thermal shock stability.

6. The influence of ultrafine powder. In the low cement castable, silica powder plays an important role, it is good for reducing the amount of water added, improving the hydration bonding strength, and can improve the compressive strength by increasing the amount of silicon powder.

In addition, 0.8~1.2‰ sodium hexametaphosphate is added to the artesian material, and the flow value of the artesian material reaches the best. It can act as both a dispersant and a water reduction, and these two properties are significantly better than sodium tripolyphosphate.

Self-flowing refractory castables are not small particles, add water more fluidity is good, it needs to be formulated by adding different binders, not only good fluidity, but also high strength.