Raw Materials Used for Manufacturing High Alumina Bricks (Complete Guide)

Raw Materials Used for Manufacturing High Alumina Bricks (Complete Guide) 

High Alumina Bricks are one of the most widely used refractory materials in industries such as steel, cement, glass, and non-ferrous metallurgy. Their performance largely depends on the quality, selection, processing, and proportioning of raw materials. 

High alumina bricks typically contain 48% to 90%+ Al₂O₃, derived mainly from bauxite and other alumina-rich materials. 

1. Bauxite – The Primary Raw Material 

Overview 

Bauxite is the most important raw material for high alumina bricks. It provides the bulk of alumina (Al₂O₃). 

• Composition: Gibbsite, Boehmite, Diaspore
• Role: Forms mullite and corundum phases during firing
• Required purity: High Al₂O₃, low Fe₂O₃ and SiO₂

Major Global Sources 

• Australia (largest reserves)
• Guinea (high-grade bauxite)
• China (Shanxi, Henan, Guizhou)
• India (Odisha, Gujarat, Jharkhand)
• Brazil

Processing Before Use 

• Crushing & screening
• Calcination (1200–1700°C) → removes moisture
• Formation of bauxite clinker
• Grinding into required grain sizes 

👉 Calcination improves density, strength, and refractoriness.

Usage in Brick Grades

Brick Grade	Bauxite Usage
50–60% Al₂O₃	Low-grade calcined bauxite
60–75% Al₂O₃	Medium-grade bauxite
75–90% Al₂O₃	High-grade / Super-grade bauxite

2. Alumina (Fused & Sintered) 

Overview 

Alumina is used when very high purity and performance are required.

• Purity: Up to 98–99% Al₂O₃
• Forms corundum phase → highest refractoriness 

Sources

• Produced globally from bauxite (Bayer process)
• Major producers: China, Australia, USA, India

Application 

Used in 80–90%+ Al₂O₃ bricks 

• Improves: Hot strength
• Slag resistance
• Wear resistance

3. Kaolin / Fireclay (Binder Material)

Overview 

Acts as a binder and plastic material. 

• Provides workability during shaping
• Supplies silica → helps mullite formation 

Sources 

• China (largest producer)
• India (Rajasthan, Gujarat)
• USA
• UK
• Brazil

Processing 

• Washing → removes impurities
• Drying & pulverizing

Role in Bricks 

Used in lower & medium grade bricks

Enhances: 

• Plasticity
• Green strength
• Workability

4. Mullite (Natural / Synthetic) 

Overview 

 Mullite (3Al₂O₃·2SiO₂) is the key high-temperature phase in refractory bricks. 

 Improves: 

• Thermal shock resistance
• Creep resistance
• Stability 

Sources 

• Synthetic production (dominant)
• Natural (rare) 

Processing 

• Produced by: Calcining kaolin
• Fusing alumina + silica 

Application 

Used in premium and high-performance bricks 

5. Corundum (High Purity Alumina Phase)

 Overview 

Corundum is pure crystalline Al₂O₃, used in extreme conditions. 

• Refractoriness: up to 1800°C+ 

Usage 

• Ultra-high grade bricks (90%+ Al₂O₃)
• Steel & glass furnaces 

6. Additives & Minor Raw Materials 

Common Additives: 

• Zircon (ZrO₂) → corrosion resistance
• Chromite → slag resistance
• Graphite → thermal shock resistance
• Phosphate binders 

Raw Material Processing Flow 

Step-by-Step: 

1. Raw material selection
2. Crushing & grinding
3. Calcination (bauxite, clay)
4. Screening & grading
5. Batching
6. Mixing Shaping (pressing)
7. Drying Firing (1400–1800°C) 

Mixing Ratios for Different Grades 

🔹 Low Grade (50–60% Al₂O₃)

• 70–80% Bauxite
• 20–30% Fireclay 

🔹 Medium Grade (60–75% Al₂O₃) 

• 60–70% Bauxite
• 10–20% Clay
• 10–20% Mullite 

🔹 High Grade (75–90% Al₂O₃) 

• 50–60% High-grade bauxite
• 20–30% Alumina
• 10–20% Mullite 

🔹 Super Grade (90%+ Al₂O₃) 

• 60–80% Alumina/Corundum
• 10–20% Mullite
• Minimal clay 

🎯 Raw Material Selection Strategy 

Application	Recommended Raw Material
Cement Kiln	Medium-grade bauxite + clay
Steel Furnace	High-grade bauxite + alumina
Glass Furnace	Corundum + mullite
Extreme Temp (>1700°C)	Fused alumina + corundum

💡 Key Insights for Industry Professionals 

Bauxite quality defines base performance
Alumina & corundum define high-end performance
Mullite improves durability & thermal shock resistance
Clay controls shaping & cost
Raw material purity directly impacts brick life & furnace efficiency 

🏁 Conclusion 

The manufacturing of high alumina bricks is not just about alumina percentage, but about: 

✔ Correct raw material selection
✔ Proper processing
✔ Optimized mixing ratios
✔ Application-specific design 

 Understanding raw materials in depth allows manufacturers to optimize cost, performance, and service life of refractory linings.