Components, systems and materials › Construction materials › Portland pozzolana cement
Portland pozzolana cement
What it is
PPC is Portland cement blended with a pozzolana such as fly ash.
Where it is used
General building and infrastructure concrete, mortar and plaster, and especially mass concrete, marine works, sewers and foundations in aggressive soils where lower heat and better durability matter.
How it works
Clinker hydrates as in OPC and releases calcium hydroxide. The pozzolana, usually fly ash, has silica in a reactive glassy form that slowly reacts with this calcium hydroxide to form additional calcium silicate hydrate. The extra gel fills pores, so mature PPC concrete is denser and less permeable. Because the pozzolanic reaction is slower, early strength is lower and curing must continue longer.
Types
- Fly ash based
- calcined clay based
Materials
Clinker, gypsum and pozzolana.
IS 1489 Part 1 covers fly ash based PPC and Part 2 calcined clay based PPC. The fly ash content in fly-ash PPC lies within a set band, with an upper limit of 35 percent by mass. Concrete mixes with PPC are designed by the same mix-proportioning method; durability provisions in IS 456 such as minimum cement content and maximum water-cement ratio still apply. Other codes classify blended cements differently, such as EN 197-1 CEM II and CEM IV types and AS 3972 blended cements.
Installation and QA steps
- Store and handle like OPC
- Plan for longer curing, typically longer than for OPC concrete in the same exposure
- Protect from early drying, especially in hot weather
- Test cubes at 28 days and, where useful, later ages
- Low early strength when formwork is struck too early
- Surface dusting from short curing
- Slower strength gain in cold weather mistaken for poor quality
Codes cited
- IS 1489 (Parts 1 and 2) (India): Portland pozzolana cement (fly ash and calcined clay based).
- EN 197-1 (Europe): Cement: composition and conformity of common cements.
- AS 3972 (Australia): General purpose and blended cements.
Cited by number only. We do not reproduce code text, tables or figures.
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