Differing from non cement refractory castable, which uses chemical binder or polymerization binder, no cement castable adopts oxides, synthesized compound micro powder or collosol as binder, which’s chemical composition is the same as castable main material. No cement castable has low impurity content, so the refractoriness and slag corrosion resistance is higher than cement refractory castable. What’s more, there will generate self bonding during using and can contribute to enhancing high temperature structural strength.
Silica micro powder bonded castable, clay bonded castable, silicon collosol or alumino silicate bonded castable all belong to no cement refractory castable. No cement castable is composed of refractory aggregate and fines, oxides micro powder or collosol, little amount of dispersant and adequate delayed action coagulant.
The micro powder should be less than 10μm, the finer the micro powder is, the better the coagulation effect is. The oxides micro powder used in for no cement castable are SiO2, Al2O3, Cr2O3, ZrO2, MgO and green refractory clay powder, etc.
No Cement High Alumina Castable Parameters
Item
70%~89% Al2O3, less than 0.2% CaO
110℃, 24h
1500℃, 3h
Bulk Density(110℃, 24h) g/cm3
2.7~2.8
2.65~2.75
Modulus of Rupture (110℃, 24h) Mpa
3.5~4.5
13~15
compression strength (110℃, 24h) Mpa
12~15
90~100
Linear change rate(1350℃) %
0 ~ -0.05
+0.5~+1.0
The physical property of oxides bonded no cement castable or collosol bonded no cement castable is similar to low cement castable and ultra low cement castable. But as impurity content is lower and low melting point eutectics is fewer in no cement castable, the refractoriness and high temperature structural strength is better than low cement and ultra low cement castable. No cement castable will form ceramic bonding during sintering and the bonding strength is gradually increased with the raise of heat treatment temperature. Differing from calcium aluminate cement bonded castable, no cement castable have higher strength after middle and high temperature heat treatment than low temperature dried.
No Cement Castable Application
What kind of binder should be chose for no cement castable depends on chemical composition of aggregate, for instance, corundum castable should use active alumina, or alumina micro powder added with silica micro powder as binder. Aluminum silicate castable should use silica micro powder or silicon collosol as binder. The coagulation and hardening speed of no cement castable is slower than calcium aluminate cement bonded castable, structural strength after room temperature maintenance is relatively lower, so it is suitable for the direct casting of integral inner lining. The max working temperature of no cement castable is higher than cement bonded castable, is usually used as high temperature vessels inner linings which’s working condition is more harsh, such as induction furnaces integral inner lining, ladles integral inner linings, etc.
