IS 8112 fixes the OPC 43 physical acceptance: minimum fineness (Blaine specific surface, IS 4034), initial and final setting time, soundness (Le-Chatelier and the autoclave test, IS 4031 Part 8) and compressive strength at 3, 7 and 28 days (IS 4031 on IS 650 sand; ≥ 43 N/mm² at 28 days). Soundness is a binary safety gate; the 28-day strength assigns the grade.
Key Requirements
•Fineness ≥ specified minimum specific surface (Blaine, IS 4034)
•Initial setting time ≥ minimum; final setting time ≤ maximum
•Soundness within limits (Le-Chatelier + autoclave, IS 4031 Part 8) — a fail is an absolute reject
•Compressive strength: 3-day, 7-day and ≥ 43 N/mm² at 28 days (IS 4031 on IS 650 sand)
•Tested on a representative sample (IS 3535); consistency (IS 4031 Part 3) sets the test water
Practical Notes
✓Soundness is non-negotiable — an unsound cement destroys hardened concrete with no remedy; the autoclave catches the slow MgO type Le-Chatelier can miss.
✓Disputed 'failing OPC 43' usually traces to the test chain (IS 650 sand, consistency-set water, compaction, calibrated CTM) — audit it before condemning the cement.
Common Mistakes
⚠Accepting on 28-day strength alone, ignoring soundness/setting/fineness.
⚠Le-Chatelier only (can miss MgO unsoundness — use the autoclave too).
⚠Non-representative sample invalidating the physical profile.