Three clinkers, three cements
Clinker is not an end product: it is bought by whoever does the grinding, and the right chemistry depends on the cement coming out of the mill.
| Parameter | Grey — Type I / II | Type V (sulfate-resisting) | White |
|---|---|---|---|
| CaO | 63–67% | 63–66% | 66–69% |
| SiO₂ | 20–23% | 21–24% | 22–24% |
| Al₂O₃ | 4.5–6.5% | 3–4.5% | 3.5–5% |
| Fe₂O₃ | 2.5–4.5% | 4–5% | max 0.35–0.4% |
| MgO | max 5–6% | max 5% | max 1–2% |
| Free CaO | max 1.5% | max 1% | — |
| Defining limit | LSF 92–98 | C₃A max 5% | Whiteness min 85–92% |
These are typical production ranges for the kiln lines we ship from, not a single certificate: clinker chemistry moves within a band from run to run. SO₃ figures apply to raw clinker before gypsum is interground. Each vessel ships against a batch mill certificate with the actual oxide analysis.
Reading a clinker before you buy it
A grinding plant reads a clinker through its four Bogue phases. C₃S carries early strength, C₂S late strength, and C₃A is the phase sulfate attack feeds on.
| Phase | Grey — Type I / II | Type V (SR) | White |
|---|---|---|---|
| C₃S (alite) | 50–60% | 45–55% | 65–75% |
| C₂S (belite) | 15–22% | 20–28% | 10–20% |
| C₃A (aluminate) | 6–10% | max 5% | — |
| C₄AF (ferrite) | 8–12% | 10–13% | < 0.5% |
- Lime saturation factor (LSF 92–98) shows how much of the lime the silica, alumina and iron can actually combine with. Run it too high and free lime is left over.
- Silica modulus (SM 2.3–2.7) sets how much liquid phase forms in the kiln, which governed how the clinker burnt.
- Alumina modulus (AM 1.3–1.7) sets the split between C₃A and C₄AF, which is why the Type V grade runs a lower one.
- Free lime (max 1–1.5%) hydrates slowly after the concrete has set and expands as it does. A low figure says the whole burn was sound, not just one number.
- Type II cement is ground from grey clinker held to a maximum of 8% C₃A, rather than the full grey band.
Routes to Iraq, Afghanistan and Central Asia
Clinker normally moves by bulk vessel, but most of these markets are reached over land:
- Iraq: overland across the land border by truck, or by sea to Iraqi ports from Bandar Imam Khomeini.
- Afghanistan and the Central Asian republics: landlocked, so overland by truck and rail through Iran's land borders on DAP or FCA terms.
- GCC and South Asia: bulk vessel FOB, CFR or CIF from Bandar Abbas or Bandar Imam Khomeini.
| Item | Terms |
|---|---|
| Minimum order | 500 MT for a bulk vessel; 1 × 20 ft container (approx. 25 MT) in jumbo bags for trial quantities |
| Packaging | Bulk as standard; 1–1.5 MT woven jumbo bags for containers, moisture-barrier liner on request |
| Lead time | 7–14 days for standard grades after order confirmation |
| Certification | Batch mill certificate per shipment: full oxide analysis, calculated Bogue phases and free lime; SGS or Bureau Veritas at the buyer's cost |
| HS code (6-digit) | 2523.10 (cement clinker) — national subheadings vary |
Clinker tolerates the journey far better than ground cement, but it is not inert: long exposure pre-hydrates the alite surface and slakes the free lime, and both cost strength once the material is ground. Keep it covered, off wet ground, and grind it in rotation.
Qualifying a clinker for your mill
- Tell us the cement you make — Type I, II, V, a blended cement or white — and we match the clinker line to it.
- Run a trial container of about 25 MT through your own mill before committing a cargo.
- Check the mill certificate on every lot against the band you contracted, especially C₃A for Type II and V and free lime for soundness.
- Ask for a tighter band if your process needs one; custom production is quoted against your target chemistry.
Frequently asked questions
What is the difference between grey, Type V and white clinker?
What they are cut for. Grey is the general-purpose feed for Types I and II. Type V lowers alumina and raises iron to keep C₃A at 5% or less for sulfate resistance. White holds Fe₂O₃ below 0.4%, Mn₂O₃ below 0.03% and Cr₂O₃ below 0.003%, because those oxides colour a cement.
Are the published figures from a certificate?
No. They are typical production ranges for the kiln lines we ship from. Each shipment carries a batch mill certificate with the actual oxide analysis, Bogue phases and free lime.
How does clinker reach Afghanistan and Central Asia?
Overland, by truck and rail through Iran's land borders, on DAP or FCA terms.
What is the minimum order?
500 MT for a bulk vessel. For a mill trial, about 25 MT in jumbo bags in a 20 ft container.
Why is free lime capped?
Free CaO hydrates after the concrete has set and expands, which shows as unsoundness and delayed cracking. It is also the clearest sign of an underburnt kiln.
Which HS code applies?
2523.10, cement clinker. National subheadings vary by destination.