IS 1489 fixes the PPC physical acceptance — fineness, initial/final setting time, soundness (Le-Chatelier/autoclave) and compressive strength at 3, 7 and 28 days (IS 4031 on IS 650 sand). The strength criteria reflect PPC's nature: slower early strength than OPC by design (the pozzolanic reaction is slow) with later strength meeting or exceeding it — accept at the specified age, not on an OPC clock.
Key Requirements
•Fineness (PPC is typically finer than OPC), initial/final setting time within limits
•Soundness within limits (Le-Chatelier / autoclave, IS 4031 Part 8) — a fail is an absolute reject
•Compressive strength at 3 / 7 / 28 days per IS 1489 (slower early gain than OPC by design)
•Accept at the specified age — not on an OPC-equivalent 7-day expectation
•Tested on a representative sample (IS 3535); consistency (IS 4031 Part 3) sets the test water
Practical Notes
✓PPC's lower early strength is the spec working as intended (slow pozzolanic reaction) — judging it against OPC's 7-day strength is the classic acceptance error.
✓Soundness remains a binary safety gate, same as OPC — an unsound PPC is an absolute reject.
Common Mistakes
⚠Rejecting PPC for low early strength judged on an OPC timeline.
⚠Le-Chatelier only (use autoclave too for MgO).
⚠Non-representative sampling invalidating the profile.