What is the production principle of castables and refractory plastics?

As two important types of amorphous refractory materials, castables and refractory plastics have significant differences in their production principles in terms of raw material composition, bonding mechanisms, and process routes. The following is a comparative analysis of the production principles of the two:

1、 Production principle of castables

Ingredient Composition

Aggregates and powders: refractory aggregates such as corundum, high alumina alumina, mullite, etc. (accounting for 60% -85%) are mainly used, and fine powders (such as SiO ₂ micro powder, Al ₂ O3 powder) are used to fill the pores.

Bonding agent: Hydraulic (Portland cement), air hardening (water glass) or fire hardening (phosphate) bonding agent, which forms strength through hydration reaction, chemical bonding or high-temperature sintering.

Admixtures: Water reducing agents, coagulants, etc. regulate fluidity or setting time.

Core Process Principles

Liquidity forming: By adding water (5% -8%) and stirring, a high fluidity slurry is formed. The mold is filled by vibration casting, and the initial strength is achieved through hydration reaction or chemical cross-linking of the binder.

Graded particle design: The aggregate adopts a three-level grading system (coarse, medium, and fine particles).

Maintenance and baking: After demolding, it needs to be naturally cured for more than 24 hours, and then dehydrated and hardened according to the 72 hour baking curve.

key equipment

Forced mixer (mixing), vibrating rod (compacting), high-temperature baking kiln.

2、 Production principle of refractory plastic

Ingredient Composition

Aggregate and clay: Aggregate accounts for 70% -85%, while clay (10% -25%) serves as a plastic carrier, imparting plasticity and preservation.

Bonding agent: Adhesive bonding (tar, asphalt) or chemical bonding (phosphate), formed by heating and sintering clay or carbonizing organic bonding agents to form strength.

Additives: Plasticizer (oxalic acid), preservative (lignosulfonate) extend plasticity.

Core Process Principles

Plastic forming: After mixing, it forms a paste like texture (with a water content of 5% -10%), which is compacted by pounding or squeezing, relying on the adhesion of clay and mechanical interlocking between particles to maintain its shape.

Trapped materials and exhaust: After mixing, the materials need to be trapped for 24 hours to eliminate bubbles. During construction, exhaust holes should be pierced to prevent baking and bursting.

High temperature sintering: During baking, the clay dehydrates and vitrifies, and the binder carbonizes or reacts with phosphate to form high temperature strength.

key equipment

Mixing machine (kneading), squeezing machine (forming), air hammer (pounding).

3、 Comparative Summary

Characteristics of castables: Fire resistant and plastic forming principle, flowability slurry+vibration compacted plastic mud+pounding/extrusion compaction bonding mechanism, hydration/chemical bonding (at room temperature), adhesion+sintering (at high temperature) process, core particle size distribution optimization, rapid dehydration clay plastic control, trapped material exhaust, suitable for complex shapes, overall pouring (such as boiler lining), local repair or irregular parts (such as pipe bends)

4、 Technological development trends

Castable material: Developing towards self leveling and low cement direction, reducing water addition while improving high temperature performance.

Plastic: Develop environmentally friendly binders (such as resin replacing tar) to extend shelf life and reduce baking energy consumption.

The fundamental difference in production principles between the two lies in the selection of binder types and molding methods, which need to be comprehensively selected based on construction efficiency, cost, and working conditions.