IS 455 specifies Portland Slag Cement — OPC clinker blended with granulated blast-furnace slag (GGBS, conforming to IS 12089) within a permitted proportion. The slag is latent-hydraulic: activated by the lime and alkalis from clinker hydration it forms additional C-S-H, giving a denser, low-permeability, low-heat, chemically-resistant binder. Slag glass content (IS 12089) is fundamental to reactivity.
Key Requirements
•PSC = OPC clinker + GGBS (IS 12089) within the IS 455 permitted slag proportion
•Slag is latent-hydraulic — activated by clinker lime/alkalis; high glass content (IS 12089) is essential
•Higher slag proportion → more durability/low-heat benefit but slower early strength
•Cite the current IS 455 edition; performance presumes IS 12089-conforming slag
•Read with the cement-spec family — OPC IS 269/IS 8112, PPC IS 1489
Practical Notes
✓The whole PSC benefit hinges on slag glass content (IS 12089) — crystalline/poorly-granulated slag is near-inert; the input spec is part of the cement spec.
✓PSC behaves like the slag analogue of PPC — a slow-reacting, curing-dependent SCM cement.
Common Mistakes
⚠Assuming any slag works (ignoring IS 12089 glass-content conformity).
⚠Treating PSC as 'diluted OPC' rather than a latent-hydraulic system.
⚠Citing a withdrawn edition / unspecified slag proportion.