May 21, 2026 · viseray
Tabular Alumina for Refractories: Properties and Selection Guide
Tabular alumina is the gold standard aggregate for high-performance refractories. Understand its properties, how it compares to calcined and reactive alumina, and how to select the right grade.
What Makes Tabular Alumina Different
Tabular alumina is produced by sintering calcined alumina at temperatures above 1900°C — near its melting point. The result is a dense, hard, almost fully alpha-phase aggregate with a characteristic tablet-like crystal morphology. This extreme processing is what gives tabular alumina its unique properties.
Key Properties
- Alpha-Al₂O₃ ≥ 98% — essentially all alpha phase. No phase transformation, no associated volume change in service.
- Apparent porosity < 5% — dense, with closed spherical pores. Low porosity means low slag and metal penetration.
- Bulk density 3.5–3.6 g/cm³ — high density contributes to high thermal mass and wear resistance.
- Refractoriness > 1800°C — suitable for the most demanding high-temperature applications.
- Thermal shock resistance — the closed porosity structure absorbs thermal stress, making tabular alumina far more thermal-shock-resistant than fused alumina.
Tabular vs Calcined vs Fused Alumina
| Property | Tabular Alumina | Calcined Alumina | Fused Alumina |
|---|---|---|---|
| Alpha-Al₂O₃ content | ≥ 98% | 92–96% | ≥ 99% |
| Apparent porosity | 2–5% | High (powder) | < 1% |
| Crystal morphology | Tabular (plate-like) | Equiaxed | Blocky, glassy |
| Thermal shock resistance | Excellent | N/A (fine powder) | Poor |
| Typical use | Aggregate (0.2–6 mm) | Matrix fines | Abrasives, monolithics |
Tabular alumina sits between calcined and fused: more phase-stable than calcined, far more thermal-shock-resistant than fused.
Grade Selection
Tabular alumina is graded by particle size fraction, not by chemistry. Standard size fractions:
| Grade | Size (mm) | Typical Application |
|---|---|---|
| 6–10 / 3–6 / 1–3 | Coarse aggregates | Steel ladle castables, precast impact pads |
| 0.5–1 / 0.2–0.6 | Medium aggregates | Shotcrete, gunning mixes, repair materials |
| 0–0.5 / 0–0.2 | Fine fractions | Self-flow castables, mortar joints |
| 0–0.045 (325 mesh) | Superfine filler | Low-cement castable matrix, along with reactive alumina |
The key to a dense castable is the right aggregate grading curve. A typical Andreasen or Dinger-Funk packing model will use 3–4 size fractions of tabular alumina, with the matrix filled by calcined or reactive alumina fines.
Combining Tabular Aggregate with Reactive Matrix
The best-performing low-cement castables use tabular alumina as the aggregate skeleton and reactive alumina as the matrix component:
- Tabular aggregate provides volume stability, thermal shock resistance, and wear resistance.
- Reactive alumina fines (D50 1–5 μm, BET 3–8 m²/g) fill the voids between tabular particles and sinter during first heat-up, bonding the structure together.
- Calcined alumina fines (D50 5–30 μm, BET < 2 m²/g) act as intermediate fillers, improving particle packing without excessive water demand.
This is why viseray offers all three types — tabular, reactive, and calcined — as coordinated grades for refractory formulation.
Practical Tip
When you receive tabular alumina, check the particle size distribution before use. Fines generated during transport can shift the grading curve and throw off your packing design. A quick sieve analysis on each shipment prevents this.
For full specifications and grade availability, see our tabular alumina product page, or contact our technical team with your application requirements.