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

The maximum allowed Loss on Ignition is 5.0% by mass as per Table 1.

What is the minimum fineness required for fly ash?

The minimum fineness is 320 m²/kg when tested by Blaine's permeability method (Table 2).

How is fly ash classified based on calcium oxide content?

It is classified as Siliceous (reactive CaO less than 10%) and Calcareous (reactive CaO 10% or more).

What is the minimum compressive strength requirement for fly ash blended concrete?

It must achieve at least 80% of the compressive strength of the corresponding plain cement concrete control mix at 28 days (Table 2).

IS 3812 Part 1

: 2013

Pulverized Fuel Ash - Specification - Part 1: For use as pozzolana in cement, cement mortar and concrete

CurrentFrequently UsedSpecificationMaterials Science · Cement

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This standard specifies the physical and chemical requirements for pulverized fuel ash (fly ash) used as a pozzolanic material in Portland pozzolana cement, mortar, and concrete. It classifies fly ash into siliceous and calcareous types based on reactive calcium oxide content and ensures its suitability for safe and durable construction.

Specifies requirements for pulverized fuel ash (fly ash) for use as a pozzolanic material in cement, mortar, and concrete.

Quick Reference Values

minimum fineness blaine320 m²/kg

maximum loss on ignition5.0 % by mass

minimum lime reactivity4.5 N/mm²

minimum compressive strength 28 days80 % of control mix

maximum soundness autoclave expansion0.8 %

maximum total chlorides0.05 %

minimum drying shrinkage0.15 %

Practical Notes

Unburned carbon in fly ash (indicated by Loss on Ignition) can significantly increase water demand and absorb chemical admixtures like air-entraining agents, requiring dosage adjustments.

Siliceous fly ash is mainly pozzolanic, whereas calcareous fly ash possesses both pozzolanic and inherent cementitious properties.

Regular testing of fineness and lime reactivity is crucial as fly ash quality can vary significantly depending on the power plant's coal source and combustion process.