Every PPC characteristic flows from one fact: the pozzolanic reaction is slow and needs moisture and time. Hence lower heat of hydration (good for thick/hot pours), a refined low-permeability pore structure and better durability — but slower early strength. PPC therefore rewards good curing and punishes poor curing far more than OPC: under-cured PPC ends up more permeable than under-cured OPC, inverting the durability case.
Key Requirements
•Design and accept to the specified (later) age — not an OPC 7-day clock
•Extended moist curing is non-negotiable (the pozzolanic reaction is still proceeding)
•Allow longer formwork stripping / loading times than OPC
•Do not over-cement to force early strength (negates the low-heat/economy benefit)
•Exploit the low heat in thicker/hot-weather pours; ensure IS 3812/IS 1344 conforming pozzolana
Practical Notes
✓Most 'PPC is weak' complaints are 'PPC was treated like OPC' complaints — stripped early, cured short, judged on 7-day strength.
✓Under-cured PPC is MORE permeable than under-cured OPC — the durability advantage inverts if curing is skimped.
Common Mistakes
⚠Stripping formwork / loading on an OPC timeline.
⚠Short curing (forfeits PPC's durability and strength).
⚠Over-cementing to chase early strength (kills the heat/economy benefit).