IS 3812:2021 Part 1 is the Indian Standard (BIS) for pulverized fuel ash - specification: part 1 for use as pozzolana in cement, cement mortar and concrete. This standard specifies the chemical and physical requirements for pulverized fuel ash (fly ash) intended for use as a pozzolana in the manufacture of Portland pozzolana cement, and as an admixture in cement mortar and concrete.
Specifies requirements for pulverized fuel ash (fly ash) for use as a pozzolanic admixture in cement, mortar, and concrete, improving their properties.
Overview
- Status
- Current
- Usage level
- Frequently Used
- Domain
- Materials Science — Roads and Pavement
- Type
- Specification
Also on InfraLens for IS 3812
Practical Notes
! High Loss on Ignition (LOI) in fly ash can significantly increase the demand for air-entraining and water-reducing admixtures, negatively impacting concrete workability.
! Always verify the fineness of fly ash; coarser fly ash (retained heavily on a 45-micron sieve) will exhibit poor pozzolanic activity and lower concrete strength.
! Calcareous fly ash (often from lignite coal) has higher reactive calcium content than siliceous fly ash, affecting early strength development.
Frequently referenced clauses
fly ashpulverized fuel ashpozzolanacementconcrete
International Equivalents
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Key Values7
Quick Reference Values
Fineness (Blaine's specific surface)Min 320 m2/kg
Particles retained on 45-micron sieve (wet sieving)Max 34%
Loss on ignition (LOI)Max 5.0%
Moisture contentMax 2.0%
SiO2 + Al2O3 + Fe2O3 (Siliceous Fly Ash)Min 70.0% by mass
SiO2 + Al2O3 + Fe2O3 (Calcareous Fly Ash)Min 50.0% by mass
Compressive strength at 28 daysMin 80% of control mix strength
Tables & Referenced Sections
Key Tables
Table 1 - Chemical Requirements
Table 2 - Physical Requirements
Key Clauses
Clause 4 - Classification of Fly Ash
Clause 5 - Chemical Requirements
Clause 6 - Physical Requirements
Clause 8 - Sampling and Testing
Frequently Asked Questions3
What is the maximum allowed Loss on Ignition (LOI) for fly ash in concrete?+
5.0% by mass as per Table 1. (Can be extended up to 7.0% if agreed upon for certain specific applications).
What is the required fineness for fly ash used as pozzolana?+
It must have a minimum specific surface area of 320 m2/kg or maximum 34% retention on a 45-micron sieve (Table 2).
What is the difference between siliceous and calcareous fly ash?+
Siliceous fly ash has reactive calcium oxide less than 10%, while calcareous fly ash has reactive calcium oxide between 10% and 25%.
QA/QC Inspection Templates
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