GGBFS Grades: S75, S95 & S105 (ASTM C989 Grade 80/100/120) Explained
Back to ResourcesQuick answer: S75, S95 and S105 are Chinese GGBFS strength-activity grades. They broadly align with ASTM C989 Grade 80, Grade 100 and Grade 120, but the systems are not identical. Select the grade from the project standard and verify the actual production lot with a batch COA.
1. How GGBFS Is Graded
GB/T 18046 classifies ground granulated blast-furnace slag as S75, S95 or S105 using strength activity at 7 and 28 days together with physical and chemical limits. ASTM C989 uses Grade 80, 100 and 120. The labels express a similar performance ladder, but each contract should cite one governing standard rather than treating the labels as legally interchangeable.
2. S75, S95 and S105 Comparison
| Property | S75 / Grade 80 | S95 / Grade 100 | S105 / Grade 120 |
|---|---|---|---|
| 7-day activity index | — | ≥ 75% | ≥ 95% |
| 28-day activity index | ≥ 75% | ≥ 95% | ≥ 115% |
| Blaine fineness | ≥ 350 m²/kg | ≥ 400 m²/kg | ≥ 450 m²/kg |
| Glass content | ≥ 85% | ≥ 85% | ≥ 85% |
| Sulfide sulfur | ≤ 2.5% | ≤ 2.5% | ≤ 2.5% |
| SO3 | ≤ 4.0% | ≤ 4.0% | ≤ 4.0% |
| Loss on ignition | ≤ 3.0% | ≤ 3.0% | ≤ 3.0% |
| Moisture | ≤ 1.0% | ≤ 1.0% | ≤ 1.0% |
The ASTM labels above are practical performance counterparts for buyer comparison, not a declaration that GB/T 18046 and ASTM C989 are identical standards. Confirm the contract test method and acceptance limits.
3. Choose the Right Grade
S75 / ASTM Grade 80
Use where moderate activity is acceptable and later-age strength, heat reduction and cost efficiency matter more than early strength. Confirm the 28-day activity requirement for the mix design.
S95 / ASTM Grade 100
The usual general-purpose choice for ready-mix and precast concrete. Miningsun's published specification lists ≥75% at 7 days, ≥95% at 28 days and Blaine ≥400 m²/kg.
S105 / ASTM Grade 120
Use for demanding high-performance concrete where a higher activity level is specified. The published table lists ≥95% at 7 days, ≥115% at 28 days and Blaine ≥450 m²/kg.
4. Quality Checks Beyond the Grade
Fineness drives water demand and early reaction, while glass content indicates the reactive phase available in the slag. Moisture matters commercially because wet material can cake, discharge poorly and add non-functional shipment weight. Require these values on the lot-specific COA together with SO3, sulfide sulfur and loss on ignition.
5. How to Verify a GGBFS Supplier
- Ask for the current batch COA, not only a generic technical data sheet.
- Name the governing standard and grade on the inquiry and purchase order.
- Check activity index, Blaine, glass content, moisture, SO3, sulfide sulfur and LOI.
- Confirm packaging, loading port and independent SGS/BV inspection requirements before production.
- Retain a sealed pre-shipment or arrival sample for contract verification.
Frequently Asked Questions
Is S95 the same as ASTM C989 Grade 100?
S95 is commonly treated as the closest practical counterpart to ASTM Grade 100, but the standards use different test frameworks. Cite the required standard in the contract and verify the batch against its actual limits.
Which GGBFS grade is most common for concrete?
S95 / Grade 100 is the usual general-purpose option because it balances activity, availability and cost. The mix designer should still validate dosage and strength development with local cement and aggregates.
Does a higher Blaine number always mean better GGBFS?
No. Higher fineness can improve early reaction but can also change water demand and handling. Activity results, chemistry, glass content and consistency between lots matter alongside Blaine fineness.
Need a batch COA or delivered GGBFS quote?
Send the required grade, standard, quantity and destination port. Miningsun will confirm available documents, packing and FOB/CIF options.
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