What is the primary performance requirement for fly ash in this standard?

The primary requirement is Lime Reactivity, which must be a minimum of 4.0 N/mm² compressive strength at 28 days (Table 2).

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

The maximum permissible LOI is 12.0 percent by mass (Table 1).

Can fly ash conforming to this standard be used for making Portland Pozzolana Cement (PPC)?

No. This standard is specifically for applications with lime. Fly ash for manufacturing PPC is governed by IS 3812 and IS 1489 (Part 1).

What is the minimum fineness specified for this type of fly ash?

The minimum fineness, tested by Blain's air permeability method, is 250 m²/kg (Table 2).

IS 15648

: 2006

Pulverized fuel ash for lime-pozzolana mixture applications.

CurrentSpecializedSpecificationMaterials Science · Building Limes and Gypsum Products

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This standard specifies the requirements for pulverized fuel ash (fly ash) for use as a pozzolanic material in lime-pozzolana mixtures. It covers the essential chemical and physical properties, such as fineness, lime reactivity, and chemical composition, to ensure the quality and performance of the ash for producing materials like mortars, plasters, and masonry blocks.

Pulverized fuel ash for lime-pozzolana mixture applications.

Quick Reference Values

Lime reactivity at 28 days, min4.0 N/mm²

Fineness by Blain's air permeability method, min250 m²/kg

Loss on ignition, max12.0 %

Silica + Alumina + Ferric oxide content, min70.0 %

Magnesia (MgO) content, max5.0 %

Sulphuric anhydride (SO₃) content, max2.75 %

Practical Notes

This standard is for fly ash used with lime, which is different from IS 3812 that covers fly ash for use with Portland cement. The key differentiator is the 'lime reactivity' test specified herein.

Lime-pozzolana binders have slower strength gain compared to ordinary Portland cement. This characteristic must be considered in project timelines, particularly for formwork stripping and load application.

Controlling the 'Loss on Ignition' (LOI) is critical, as high unburnt carbon content can adversely affect workability, increase water demand, and lead to inconsistent color in the final product.