Indian Compliance
IS 16415 Composite Cement: Grade, Specifications & BIS Licence Requirements
Composite cement is one of the newer cement types in India, and also one of the most searched: "what grade is IS 16415?" The short answer is that IS 16415 has no grade designation like OPC 43 or OPC 53. It has one set of minimum strength requirements that every composite cement must meet.
This guide explains what IS 16415 composite cement is, what the standard requires, how it compares with PPC and OPC, and how manufacturers get the BIS licence to sell it.
What Is IS 16415 Composite Cement?
IS 16415 is the Indian Standard for composite cement. It was first published in 2015 and has since been amended. Composite cement is made by intergrinding or blending:
- Portland cement clinker
- Fly ash
- Granulated blast furnace slag
- Gypsum, plus permitted performance improvers
Because it uses both fly ash and slag, it can replace more clinker than PPC or PSC alone. That lowers the carbon footprint and uses industrial by-products.
IS 16415 Composition (as Amended)
| Constituent | Requirement (amended standard) |
|---|---|
| Clinker | At least 45% (or at least 50% where OPC is used) |
| Fly ash | 10% to 25% |
| Granulated blast furnace slag | 25% to 40% |
The original 2015 text allowed wider ranges (clinker 35% to 65%, fly ash 15% to 35%, slag 20% to 50%). If you are working from an old copy, update to the current amended version before setting your mix.
IS 16415 Cement Grade and Strength Requirements
Instead of grades, IS 16415 sets minimum compressive strength values. The amendment raised them significantly:
| Age | Minimum compressive strength (amended) | Original 2015 value |
|---|---|---|
| 3 days | 23 MPa | 16 MPa |
| 7 days | 33 MPa | 22 MPa |
| 28 days | 43 MPa | 33 MPa |
So in practice, composite cement made to the current standard performs at least at the level of a 43-grade cement at 28 days. Other physical requirements such as fineness, soundness and setting time, and chemical limits such as loss on ignition, magnesia, sulphate and chloride, are set in the standard and checked in testing.
Composite Cement vs PPC vs OPC
| OPC (IS 269) | PPC (IS 1489 Part 1) | Composite cement (IS 16415) | |
|---|---|---|---|
| Blending materials | None (minor additions only) | Fly ash | Fly ash and slag |
| Grades | 33, 43, 53 | No grade | No grade |
| Early strength | Highest | Lower | Moderate |
| Heat of hydration | Higher | Lower | Lower |
| Durability in aggressive environments | Good | Better | Better |
Is the BIS Licence Mandatory?
Yes. Cement types including composite cement are covered by the Cement Quality Control Order. No one may make, import, sell or store composite cement for sale without a valid BIS licence and the ISI mark. Our article on why the ISI mark is non-negotiable for cement covers enforcement in more detail.
How Manufacturers Get the BIS Licence for IS 16415
- Set up the lab. The plant needs the in-house testing listed in the BIS product manual, including compressive strength, fineness, setting time, soundness and chemical analysis.
- Prepare records. Raw material checks, mix proportions, calibration and test records.
- Apply on Manak Online with documents and fees.
- Factory inspection. A BIS officer checks the plant and lab and draws samples.
- Independent testing of samples in a BIS or BIS-recognised lab.
- Grant of licence with a CM/L number once results conform and fees are paid.
Foreign cement plants follow the same steps under FMCS.
Marking on the Bag
- ISI mark with IS 16415 and the CM/L licence number
- Manufacturer's name and brand
- Type of cement ("Composite Cement")
- Week, month and year of manufacture, and net quantity
- Other declarations required by the standard and Legal Metrology rules
Common Mistakes
- Working to the original 2015 values. The amended standard has different composition ranges and much higher strength.
- Marketing a "grade". IS 16415 has no grade designation, so do not label composite cement as 43 or 53 grade.
- Weak raw material control. Fly ash and slag quality vary by source and need regular testing.
How Instacertify Helps
We check your plant against the BIS product manual, set up records, prepare the application and support the BIS inspection through to grant. See our ISI mark for cement manufacturers page.
Frequently asked questions
What is the grade of IS 16415 composite cement?
IS 16415 does not sell composite cement by grade like OPC 43 or OPC 53. It sets a single set of minimum strength requirements, which under the amended standard are 23 MPa at 3 days, 33 MPa at 7 days and 43 MPa at 28 days.
What is composite cement?
Composite cement is made by blending Portland cement clinker with both fly ash and granulated blast furnace slag, plus gypsum. It combines the benefits of PPC and PSC in one product.
Is the ISI mark mandatory for composite cement?
Yes. Cement types including composite cement to IS 16415 are covered by the Cement Quality Control Order, so manufacturers and importers need a BIS licence and the ISI mark.
Can composite cement be used for RCC work?
It can be used for general construction, including RCC, where the design and specifications allow it. Check the structural designer’s requirements and the current IS 456 provisions before using any blended cement in reinforced concrete.
What is the difference between composite cement and PPC?
PPC blends clinker with fly ash only. Composite cement blends clinker with both fly ash and slag, which allows higher total replacement of clinker.
How do I check if composite cement is genuine?
Check the bag for the ISI mark, IS 16415, the CM/L licence number, the week and year of manufacture, and verify the licence number in the BIS Care app.