ASTM C1240 Silica Fume: What the Standard Requires (and How to Verify a Supplier)
Back to ResourcesQuick answer: ASTM C1240 sets chemical, physical and performance requirements for silica fume used in cementitious mixtures. A grade name or SiO2 percentage is not enough—compliance must be verified lot by lot against every applicable limit on the batch COA.
1. What ASTM C1240 Requires
| Property | ASTM C1240 requirement | Why buyers check it |
|---|---|---|
| Silicon dioxide (SiO2) | ≥ 85.0% | Confirms the main pozzolanic constituent. |
| 7-day strength activity index | ≥ 105% | Demonstrates performance with Portland cement. |
| Loss on ignition | ≤ 6.0% | Helps control unburned carbon and volatile matter. |
| Moisture | ≤ 3.0% | Reduces caking and non-functional shipment weight. |
| Oversize retained on 45 µm sieve | ≤ 10.0% | Checks agglomerates and coarse residue. |
| Specific surface area | ≥ 15 m²/g | Confirms the expected ultrafine particle profile. |
This is a buyer-facing summary of the principal published limits. The current edition of ASTM C1240 and the project specification govern testing, sampling and acceptance.
2. ASTM C1240, EN 13263 and GB/T 18736
ASTM C1240 is widely specified in North America and international projects using ASTM methods. EN 13263 is the European framework, while GB/T 18736 is commonly used for Chinese production and testing. They overlap on silica content, fineness and performance but are not interchangeable without contract approval.
3. How Miningsun Grades Relate to ASTM C1240
Silica Fume Grade 85
Published SiO2 is ≥85%. The published activity and LOI values do not by themselves establish full ASTM C1240 compliance. Use only when the batch COA confirms every required limit.
Silica Fume Grade 90
Published SiO2 is ≥90%. Higher silica content alone is not a substitute for the activity-index, LOI, moisture, oversize and surface-area checks required by the contract.
Silica Fume Grade 92
The published table explicitly reaches the ≥105% activity-index and ≤6% LOI thresholds. Full compliance still depends on the remaining ASTM C1240 results for the actual lot.
4. How to Verify a Silica Fume Supplier
- Request the production-lot COA and match its batch number to the bags and shipping documents.
- Check all applicable ASTM C1240 limits, not only SiO2 or a marketing grade.
- Confirm densified or undensified form and require bulk density for freight and handling calculations.
- State the test standard, sampling method and independent inspection requirement on the purchase order.
- Retain a sealed sample for buyer or third-party verification.
5. Documents to Request Before Shipment
Ask for the batch COA, technical data sheet, SDS, packing list and mill test certificate where required. For Miningsun silica fume, the quality-management system for silica fume production is ISO 9001 certified by CQC (certificate No. 00107Q12698R1S/7300).
Frequently Asked Questions
Does silica fume with 85% SiO2 automatically comply with ASTM C1240?
No. SiO2 is only one requirement. The batch must also meet the specified activity index, LOI, moisture, oversize and surface-area limits, together with the standard's applicable sampling and test provisions.
Which Miningsun grade is the closest starting point for ASTM C1240?
Grade 92 is the published option that explicitly reaches the activity-index and LOI thresholds. Approve it only after the same lot's COA confirms every remaining contractual requirement.
Does ISO 9001 certification prove ASTM C1240 compliance?
No. ISO 9001 certifies the quality-management system. ASTM C1240 compliance is a product-lot determination supported by the required test results and the batch COA.
Need a batch COA or ASTM C1240 quote?
Send the required standard, grade, form, quantity and destination port. Miningsun will confirm documents, packing and FOB/CIF options for the available production lot.
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