What is the primary difference between IS 3812 Part 1 and Part 2?

Part 1 is for fly ash used as a reactive pozzolana (partially replacing cement), whereas Part 2 is for fly ash used as an admixture or fine aggregate filler.

What is the maximum allowed Loss on Ignition (LOI)?

Up to 12.0%. High LOI levels negatively affect the efficiency of water-reducing chemical admixtures.

Which standard details the testing procedures for fly ash?

IS 1727 covers the methods of test for pozzolanic materials, which is referenced heavily by IS 3812.

IS 3812 Part 2

: 2023

Pulverized fuel ash - Specification - Part 2: For use as admixture in cement mortar and concrete

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This standard prescribes the physical and chemical requirements for pulverized fuel ash (fly ash) intended for use as an admixture or fine aggregate in cement mortar and concrete. Unlike Part 1, it focuses on fly ash acting primarily as a filler to improve workability and pumpability rather than as a reactive pozzolanic material.

Specifies requirements for pulverized fuel ash for use as an admixture in cement mortar and concrete, supporting sustainable material usage.

Quick Reference Values

Maximum Loss on Ignition (LOI)12.0 %

Maximum Magnesia (MgO) content5.0 %

Maximum Sulphuric Anhydride (SO3)3.0 %

Maximum Total Chlorides0.05 %

Practical Notes

Do not use Part 2 fly ash as a direct partial replacement for cement; it does not have the strict pozzolanic reactivity requirements of Part 1.

High Loss on Ignition (LOI) indicates unburnt carbon, which can absorb chemical admixtures like superplasticizers and disrupt air entrainment.

Highly useful for replacing a portion of fine aggregate (sand) to improve the cohesiveness and pumpability of the concrete mix.