IS 1727 provides test methods for evaluating pozzolanic materials used in cement and concrete. The lime reactivity test and strength activity index are the key tests that determine whether a pozzolan (fly ash, GGBS, silica fume) is suitable for use in concrete.
Methods of testing pozzolanic materials (fly ash, calcined clay, silica fume, GGBS) for use in cement and concrete, including chemical analysis, fineness, lime reactivity, and strength activity index.
Key Values
Lime reactivity min4.5 MPa
Strength activity index at 28 daysMin 80% of control
LOI max (fly ash)5.0%
Practical Notes
! Lime reactivity test is the quickest way to check if fly ash is reactive enough for use in concrete.
! Strength activity index (SAI) is the definitive test — min 80% at 28 days means the pozzolan contributes to concrete strength.
! High LOI (>5%) in fly ash indicates unburnt carbon which causes problems with air entrainment and colour.
! IS 1727 tests are mandatory for qualifying fly ash per IS 3812 before use in concrete.