Portland Puzzolana Cement (IS: 1489 (Part I)

Portland Puzzolana Cement (IS: 1489 (Part I)

Portland Puzzolana Cement (IS: 1489 (Part I): It is manufactured by grinding Portland cement clinker and puzzolana (usually fly ash 10-25% by mass of PPC) or by intimately and uniformly blending Portland cement and fine puzzolana. Puzzolana (burnt clay, shale, or fly ash) has no cementing value itself but has the property of combining with lime to produce a stable lime-puzzolana compound which has definite cementitious properties. Free lime present in the cement is thus removed. Consequently, the resistance to chemical attack increases making it suitable for marine works. The hardening of Portland puzzolana cement consists in hydration of Portland cement clinker compounds and then in interaction of the puzzolana with calcium hydroxide released during the hardening of clinker. At the same time, calcium hydroxide is bound into a water-soluble calcium hydrosilicate according to the reaction with the effect that puzzolana Portland cement acquires greater water-resisting property than ordinary Portland cement.

Ca(OH)₂ + SiO₂ + (n - 1) H₂O = CaO.SiO₂.nH₂O

Properties: These have lower rate of development of strength but ultimate strength is comparable with ordinary Portland cement.

Compressive Strength

 72 ± 1 hr    16.0 N/mm²

168 ± 2 hrs 22.0 N/mm²

672 ± 4 hrs 33.0 N/mm²

The initial and the final setting times are 30 minutes (minimum) and 600 minutes (maximum), respectively. The drying shrinkage should not be more than 0.15% and the fineness should not be less than 300 m²/kg.

Uses: It has low heat evolution and is used in the places of mass concrete such as dams and in places of high temperature.