IS 455 fixes the PSC physical acceptance — fineness, initial/final setting time, soundness (Le-Chatelier/autoclave) and 3/7/28-day compressive strength (IS 4031 on IS 650 sand). As a slag-rich binder PSC gains early strength slower than OPC by design, with later-age strength meeting or exceeding it — accept at the specified age, not on an OPC clock.
Key Requirements
•Fineness, 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 455 (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
✓PSC early strength is lower by design — judging it on OPC's 7-day strength is the classic acceptance error (same as PPC).
✓Soundness is a binary safety gate regardless of binder — an unsound PSC is an absolute reject.
Common Mistakes
⚠Rejecting PSC for low early strength on an OPC timeline.
⚠Le-Chatelier only (use autoclave too for MgO).
⚠Non-representative sampling invalidating the profile.