Calcined Clay Cement Testing: Complete Guide to Tests and Standards

• Calcined clay cement testing checks if Portland Pozzolana Cement made with calcined clay meets chemical, physical and strength limits.
• The main standard is IS 1489 Part 2, and the cement falls under the Cement Quality Control Order.
• The calcined clay itself must meet its own standard, so input testing matters as much as final cement testing.
• Fineness, setting time, soundness, strength and drying shrinkage are the core physical checks.
• Testing happens in the factory lab regularly, and in a recognised lab for outside proof.
• Under-burnt clay, poor records and old samples are the most common reasons for trouble.

---

Introduction

Think of making roti. If the tawa is not hot enough, the roti stays raw inside, no matter how good the atta is. Calcined clay is the same. If the clay is not heated properly, it does not become reactive, and the cement made with it will not perform.

This is why testing is so important. In this blog, we’ll go through what calcined clay cement is, which tests are done, how the process works and where people usually go wrong. Simple words, no heavy jargon.

---

What Is Calcined Clay Cement?

Calcined clay cement, in the BIS system, means Portland Pozzolana Cement (PPC) where the pozzolana is calcined clay. It is covered under IS 1489 Part 2. The standard also allows a mixture of calcined clay and fly ash.

What is calcined clay? It is ordinary clay that has been heated at a controlled temperature. This heating changes the clay so that it reacts with the lime released by cement during hydration. That reaction gives extra binding material and a denser structure.

Why do companies use it? Because it replaces part of the clinker, which brings down the carbon footprint. It is also useful where fly ash is hard to get.

A quick note. You may also hear about LC3, which is limestone calcined clay cement. That is a different type of cement with its own specification. Please check it separately and do not mix it up with IS 1489 Part 2.

---

What Is Calcined Clay Cement Testing?

It is the process of checking cement samples, and the calcined clay used in them, against the Indian Standard. The lab checks chemistry, physical behaviour and strength.

If every result is inside the limit, the cement passes. If even one result is outside, the lot fails.

There are two main purposes. One is daily quality control in the plant. The other is certification, where a recognised lab report is needed for the BIS licence.

---

Which Standard Applies?

Standard	What it covers
IS 1489 (Part 2)	Portland pozzolana cement, calcined clay based
IS 1489 (Part 1)	Portland pozzolana cement, fly ash based
IS 1344	Calcined clay pozzolana
IS 3812 (Part 1)	Fly ash used as pozzolana
IS 4031 (series)	Methods of physical tests on hydraulic cement
IS 4032	Method of chemical analysis of hydraulic cement
IS 269	Ordinary Portland cement, which the clinker must conform to

Simple example: A plant makes PPC using calcined clay because fly ash is expensive in its region. The cement bag carries the ISI mark and the IS 1489 Part 2 reference. The buyer can ask for the batch test certificate to see the real results.

Important note: The Cement (Quality Control) Order lists the cement standards that need the BIS Standard Mark, and IS 1489 is among them. The current edition of Part 2 is the 2015 edition, which is the fourth revision. Quality Control Orders change from time to time, so please check the BIS website and the latest notifications before you plan.

---

Why Is Calcined Clay Cement Testing Important?

• Under-calcined clay does not react well, and the cement may give low strength.
• Wrong blending can change setting time, shrinkage and durability.
• Builders, consultants and government projects ask for batch test certificates.
• It protects your brand. A bad batch spreads complaints quickly.
• It helps the plant catch problems in calcining, grinding and blending early.
• It proves that the label on the bag matches what is inside.

---

What Tests Are Conducted?

The tests fall in four groups. Calcined clay checks, chemical tests, physical tests and strength tests.

Calcined clay (input) checks

The pozzolana must meet its own standard before it goes into cement. The lab checks things like fineness, reactivity and loss on ignition of the clay. If the clay is poor, the cement will be poor, even if the rest of the process is perfect.

Chemical tests

Test	What the lab checks	In simple words
Loss on ignition	Weight lost on heating	Has the cement absorbed moisture or is clay under-burnt?
Magnesia	Magnesium oxide content	Will it expand later?
Sulphuric anhydride	Sulphate content, with a limit set in the standard	Is gypsum added in the right amount?
Chlorides	Chloride content	Is it safe for steel reinforcement?
Insoluble residue	Part that does not dissolve in acid	Does the blend match what is declared?

Physical tests

Test	What the lab checks	In simple words
Fineness	Surface area of the powder	How fine is the cement?
Setting time	Initial and final setting	When does it start and finish hardening?
Soundness	Le Chatelier and autoclave expansion	Will it swell or crack after setting?
Standard consistency	Water needed for a standard paste	Base value for other tests
Drying shrinkage	Shrinkage of mortar bars	How much will it shrink while drying?

Strength tests

Mortar cubes are made, cured in water and crushed at fixed ages, including 3, 7 and 28 days. The cement must reach the minimum strength at each age. The exact limits are given in the standard, so please confirm them in the current edition.

---

The Special Point: The Quality of Calcined Clay

This is what makes calcined clay cement testing different from ordinary cement testing. Here the cement is only as good as its pozzolana.

Clay is heated to a certain temperature range to make it reactive. If it is heated too little, it stays unreactive. If the temperature is badly controlled, the quality changes from batch to batch. The result shows up as low strength, odd setting time and high water demand.

So, a smart plant tests the clay daily, keeps the calcining temperature records and checks the declared blend against the actual dosing. During BIS inspection, officers will look at these records closely.

Tip before sending samples: Check your calcined clay test records first. Make sure the blend you declare is the same blend your feeders actually run.

Two Kinds of Testing: Factory Lab and Recognised Lab

Factory lab (in-house testing). This is your own plant lab. You test samples regularly, record results and keep them ready. BIS looks at this lab closely during factory inspection.

Recognised lab (outside testing). This is an independent lab accepted by BIS. It tests samples and gives a report. During surveillance, BIS may also draw samples from your plant or the market and send them for testing.

One gives daily control. The other gives outside proof. You need both.

Step-by-Step Process

1. Confirm the standard. Check IS 1489 Part 2 and the latest notification on cement.
2. Check your plant set-up. Calcining, grinding, blending, storage and packing should be ready.
3. Prepare the in-house lab. Arrange chemical and physical test equipment and trained staff.
4. Make a quality plan. Write checks for clinker, gypsum, calcined clay, cement and packing.
5. Make a trial lot. Produce the cement under regular conditions.
6. Test in-house. Run all the tests and record every result honestly.
7. Send samples to a recognised lab. Pack them airtight and label them clearly.
8. Apply to BIS. File the application with documents, test report and factory details.
9. Inspection and grant. BIS officers visit, check the set-up and may draw samples. If all is fine, the licence is granted.

Which BIS Route Is Needed?

Your business	Usual route
Indian cement manufacturer	ISI Mark licence under Scheme-I
Foreign cement manufacturer	BIS licence under the Foreign Manufacturers Certification Scheme
Importer or trader	Deals only in certified cement and keeps proper records
Export-only plant	May be outside the order, but confirm in the latest notification

A licence is linked to a product, a standard and a plant. If you change the plant or add a new brand, talk to BIS first.

---

Documents Required

Company documents

• Company registration or partnership deed
• Factory licence and address proof
• Authorised person details

Product and plant documents

• Product details and brand names
• Process flow chart from raw material to packing
• Plant and lab layout
• Clinker, gypsum and calcined clay supplier or production details
• Environment and safety permissions, as applicable

Testing records

• Calibration certificates of equipment
• In-house test records of recent lots
• Calcined clay test records
• Recognised lab test report
• Quality control staff details

---

How Long Does It Take?

Testing needs time mainly because of curing. The 28-day strength result alone needs four weeks.

The full licence process takes longer. Even if your papers and plant are ready, it can take a couple of months. Foreign manufacturers usually need more time.

Delays mostly come from missing documents, calibration gaps and failed samples.

---

What Decides the Cost?

No fixed number can be given here, because every plant is different. These things decide the cost:

• Number of tests in the standard
• Lab charges of the selected lab
• BIS application and licence fees
• Equipment and lab upgrades needed in the plant
• Number of brands or products you want covered
• Consultant support, if you take it

Share your plant details and ask for a clear breakup before you begin.

---

Common Failures and Easy Fixes

Problem	Likely reason	Easy fix
Low early strength	Clay not fully reactive	Check calcining temperature and clay fineness
Low 28-day strength	Poor grinding or wrong blend	Review grinding and blend dosing
High loss on ignition	Moisture entered or clay under-burnt	Improve storage and calcining control
Soundness failure	Free lime or high magnesia	Control clinker quality and raw material
Setting time out of range	Wrong gypsum or clay quality changes	Recheck gypsum dosage and test clay each day
High drying shrinkage	Blend or fineness off	Review fineness and blend ratio

---

Common Mistakes to Avoid

• Skipping tests on the calcined clay and testing only the final cement.
• Judging this cement by early strength, like you would for ordinary cement.
• Declaring a blend that does not match the actual plant dosing.
• Keeping no records of the calcining temperature.
• Sending old or half-open sample bags that have absorbed moisture.
• Using equipment that is not calibrated.
• Citing the wrong part of IS 1489, like Part 1 for a calcined clay product.
• Not tracking changes in the Cement Quality Control Order and standard revisions.

---

Who Needs This?

• Cement manufacturers making calcined clay based PPC.
• Importers bringing cement from other countries.
• Private label brands whose cement is made by another plant.
• Overseas manufacturers selling into India.
• Builders and contractors who want proof before buying in bulk.

---

Why Choose Diligence Certifications for calcined clay cement testing Certification?

Cement rules and test methods can feel heavy, especially for a first-time applicant. Practical guidance saves time and avoids mistakes.

Diligence Certifications supports manufacturers and importers with standard selection, document preparation, sample planning and application follow-up. You can visit the Diligence Certification website to know more, or check the Portland pozzolana cement certification service page for details.

We explain each step in plain language and tell you clearly what is needed. We do not promise approvals, because approval depends on your product, your plant and BIS review.

---

Quick Checklist Before Sending Samples

• Standard and product confirmed as IS 1489 Part 2
• Fresh sample drawn properly from a regular lot
• Sample packed airtight and labelled
• Calcined clay test records ready
• Declared blend matches plant records
• Equipment calibration up to date
• 28-day curing time planned in the schedule
• Bag marking checked

---

Conclusion

Calcined clay cement testing is not just paperwork. It proves that your cleaner, greener cement still performs the way the label says.

Know your standard, control the quality of your calcined clay, test honestly in your own lab and keep clean records. Do these things and most of the trouble goes away.

If you are unsure where to start, talk to an expert before you make a big batch.

---

Frequently Asked Questions