IS 1489:1991 Part 2 is the Indian Standard (BIS) for portland-pozzolana cement - part 2: calcined clay based - specification. Specifies the chemical, physical, and manufacturing requirements for Portland-Pozzolana Cement (PPC) manufactured using calcined clay. It details the acceptable limits for setting time, compressive strength, fineness, and chemical composition to ensure suitability for general construction, marine works, and mass concreting.
Specifies requirements for calcined clay based Portland-Pozzolana Cement.
Key reference values — verify against the current code edition / project specification.
| Reference | Value | Clause |
|---|---|---|
| Product | PPC with calcined-clay pozzolana (not fly ash) | Scope |
| Principle | Same pozzolanic behaviour as fly-ash PPC | Concept |
| Reactivity needs | Proper calcination/activation of the clay | Critical |
| Early strength | Slow (pozzolanic); later strength catches up | Critical |
| Heat / durability | Lower heat, refined pores — with curing | Application |
| Use when | Fly ash scarce / calcined-clay (LC3-type) wanted | Application |
| Curing | Prolonged moist curing essential | Caution |
| Pozzolana | Per IS 1344 (calcined clay) | Cross-ref |
IS 1489 Part 2:1991 is the specification for calcined-clay-based Portland-Pozzolana Cement (PPC) — the calcined-clay counterpart to fly-ash PPC (Part 1). The clinker is blended with a calcined clay pozzolana (a thermally-activated clay; the family includes metakaolin-type reactive clays) instead of fly ash, giving the same pozzolanic-cement behaviour from a different supplementary material.
It sits in the cement family:
Calcined-clay PPC behaves on the same pozzolanic principle as fly-ash PPC — the reactive (calcined) clay consumes clinker-derived calcium hydroxide to form extra C-S-H:
The engineering point is identical to fly-ash PPC: a curing-and-time cement whose benefits and slow-early-strength liability both stem from the slow pozzolanic reaction. The only practical difference is the supplementary material (calcined clay vs fly ash) — which is relevant where fly ash is unavailable or where calcined-clay/metakaolin-type reactivity is specifically wanted (calcined-clay/limestone systems are also of growing interest for low-carbon cement).
Scenario: a durability-governed structure where fly ash is scarce / a reactive calcined clay is the available pozzolana.
Step 1 — select the right PPC: calcined-clay PPC (IS 1489 Part 2) with a conforming calcined-clay pozzolana — same durability/heat goals as Part 1 fly-ash PPC.
Step 2 — design to specified age: IS 10262 mix to the design-age strength; expect slower early strength.
Step 3 — formwork/loading & curing: longer stripping/loading times; extended moist curing — the pozzolanic reaction (and the durability it confers) needs time and moisture.
Step 4 — accept at proper age per IS 456.
Step 5 — assure the pozzolana: confirm the calcined clay's reactivity/quality — under-calcined or poor clay is the calcined-clay analogue of crystalline slag or coarse fly ash.
Used correctly it delivers PPC-type durability and low heat from a non-fly-ash source; treated on an OPC clock with short curing it under-performs — the same failure mode as every pozzolanic cement.
1. OPC-timeline expectations. Like all PPC, slow early strength is by design — stripping/loading on an OPC clock fails it.
2. Short curing. Calcined-clay PPC durability comes from the slow pozzolanic reaction — under-curing makes it more permeable, not less.
3. Assuming any clay works. Reactivity depends on proper calcination/activation; under-calcined or unsuitable clay is near-inert (the calcined-clay parallel of low-glass slag).
4. Treating Part 1 and Part 2 as identical products. Same principle, different pozzolana and supply; specify the correct part for the material actually used.
5. Over-cementing for early strength. Negates the low-heat/economy purpose.
IS 1489 Part 2 is reaffirmed and the less-used PPC variant in India simply because fly ash is abundant, but it matters in two situations: where fly ash isn't available, and as part of the growing low-carbon-cement interest in calcined-clay systems (calcined clay reactivity, LC3-type binders). The engineering reality is the standard PPC one — a curing-and-time cement whose durability/heat benefits and slow-early-strength cost both come from the slow pozzolanic reaction — with the single material caveat that calcination/activation quality governs the clay's reactivity, just as glass content governs slag and fineness governs fly ash. Specify the correct part for the actual pozzolana, design and accept at the proper age, cure long, and assure the calcined clay — then it performs like any well-handled PPC; treat it like OPC and it disappoints like every mishandled pozzolanic cement.