About Burnt Dolomite (Dead-Burnt / Sintered)
Burnt dolomite, also called dead-burnt or sintered dolomite, is dolomite fired well beyond calcination temperature, typically at 1,600 °C or more. At that temperature the lime and magnesia crystals grow and the porous calcine shrinks into a dense clinker. The product shares the CaO–MgO chemistry of calcined dolomite but behaves very differently: low porosity, high bulk density and much lower reactivity with water and slag.
Those properties make burnt dolomite a refractory material rather than a flux. It is the grain in dolomite bricks and basic monolithic linings for steel ladles, AOD and VOD converters and cement kiln burning zones. It is also the main component of gunning, ramming and fettling masses used to repair the hearth and banks of electric arc furnaces between heats. Its basic chemistry is regarded as favourable for clean-steel practice, since the lime component is compatible with the desulphurising slags used in secondary refining.
Obsidian Minerals supplies burnt dolomite as graded grain fractions, with bulk density, chemistry and size agreed against the refractory producer's or melt shop's specification. Free lime in the grain can still hydrate slowly in humid air, so the product is packed in moisture-barrier bags and should be kept dry and used in rotation.
Typical specifications
| Parameter | Typical Value | Test Method |
|---|---|---|
| CaO | 55–60 % | XRF (internal method) |
| MgO | 37–41 % | XRF (internal method) |
| SiO₂ | ≤ 1.0 % | XRF (internal method) |
| Fe₂O₃ | ≤ 1.5 % | XRF (internal method) |
| Loss on ignition | ≤ 0.5 % | Internal method |
| Bulk density (grain) | ≥ 3.0 g/cm³ | ASTM C357 |
| Apparent porosity | typically 3–6 % | Internal method |
| Grain fractions | 0–1, 1–3, 3–5, 5–10 mm or as specified | Sieve analysis |
Typical values for guidance. Guaranteed bulk density, chemistry and grading are stated on the Technical Data Sheet and batch CoA.
Key features & benefits
High bulk density
Typical grain bulk density of 3.0 g/cm³ or higher reflects well-sintered burnt dolomite with a closed structure, which limits slag penetration and improves erosion resistance in the lining.
Low porosity, low reactivity
Dead burning removes almost all carbon dioxide and closes the crystal structure, so the grain reacts far more slowly with water and slag than light-burnt calcined dolomite.
Basic, steel-compatible chemistry
The balanced CaO–MgO composition is chemically compatible with basic steelmaking slags and is widely used in ladles and converters that produce low-sulphur and clean steel grades.
Graded fractions for mixes
Defined grain fractions let refractory producers and melt shops build dense packing curves for pressed bricks, gunning mixes and ramming masses, with fewer voids after installation.
Hydration control
Low residual LOI and dense grain reduce, though do not eliminate, hydration risk. Moisture-barrier packaging protects the material during export transit and storage before use.
Applications
EAF hearth fettling and repair
Thrown or gunned onto the hearth and slag line between heats, the grain sinters into the hot lining and restores worn areas, helping extend furnace campaign life.
Gunning and ramming masses
The main aggregate in basic gunning and ramming mixes for converters, ladles and furnace hearths, where dense grain and controlled sizing give a compact, slag-resistant repair.
Dolomite bricks and basic linings
Grain for pressed, pitch- or resin-bonded dolomite bricks used in steel ladles and AOD and VOD converters, and for monolithic basic working linings in secondary steelmaking vessels.
Cement kiln refractories
Dolomite bricks made from sintered grain are used in the burning zone of rotary cement kilns, where they help form and hold a protective clinker coating on the hot face of the lining.
Usage & handling
- Fettling consumption depends on furnace size and practice; plants usually set an addition per heat from trials and adjust it to observed hearth wear.
- Keep grain dry until use; damp material hydrates, loses density and breaks down into fines.
- Use the oldest stock first and reseal part-used bags immediately.
- Wear dust masks, eye protection and gloves, as the grain is alkaline and dusty.
Packaging & supply
- 1 MT and 1.2 MT jumbo bags with moisture-barrier liner
- 25 kg and 50 kg lined bags for gunning-mix producers and trial quantities
- TDS, MSDS/SDS and batch CoA with every consignment
Frequently asked questions
What is burnt dolomite?
Burnt dolomite is dolomite fired at sintering temperature, typically 1,600 °C or more, until it becomes a dense clinker of lime and magnesia crystals. It is also known as dead-burnt or sintered dolomite. Its high density and low porosity make it a basic refractory material for steelmaking vessels, furnace repair mixes and cement kilns.
Why does bulk density matter for burnt dolomite?
Bulk density is a direct indicator of how completely the grain has sintered. Denser grain has fewer open pores, so molten slag and metal penetrate it less and the lining or repair lasts longer. Lower-density grain also hydrates more readily in storage. That is why bulk density is a key acceptance parameter on refractory specifications.
Can burnt dolomite be used as a flux in the converter?
It is not the preferred choice. Because dead-burnt grain is dense and unreactive, it dissolves slowly in slag, which is an advantage in a lining but a drawback when quick MgO pick-up is needed. For fluxing and slag conditioning, the calcined dolomite grade is normally specified, while burnt dolomite is reserved for refractory and repair duty.
What grain sizes are available?
Typical fractions are 0–1 mm, 1–3 mm, 3–5 mm and 5–10 mm, which can be combined to build a packing curve for bricks or monolithic mixes. Fettling grades and other gradings can be screened to the melt shop's or refractory producer's specification. The agreed fractions are confirmed on the Technical Data Sheet.
Does burnt dolomite hydrate in storage?
Yes, slowly. Although dead burning greatly reduces reactivity, the free lime in the grain can still react with atmospheric moisture over time, causing dusting and loss of density. Keep bags sealed in a dry, covered store, avoid long holding periods, and use material in the order it was received.