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IS 17208:2019 is the Indian Standard (BIS) for guidelines for use of geopolymers in concrete. This standard provides guidelines for producing and using geopolymer concrete (GPC), an alternative to traditional cement concrete that uses industrial by-products like fly ash and GGBS as binders. It covers material specifications, mix proportioning principles, handling, placing, and specific curing requirements like heat curing.
Provides guidelines for the use of geopolymer binders in concrete, offering an alternative to ordinary Portland cement with lower carbon footprint.
Overview
Status
Current
Usage level
Specialized
Domain
Materials Science — Green Building and Sustainability
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Handling alkaline activators like Sodium Hydroxide and Sodium Silicate requires strict safety precautions (gloves, goggles, apron) as they are highly corrosive.
! The properties of GPC are highly sensitive to the source and quality of fly ash and GGBS; trial mixes are essential for every new batch of materials.
! Unlike Portland cement concrete, GPC often requires heat curing (e.g., at 60-80°C) to achieve high early strength, which must be planned for at the precast yard or site.
Guide for Alkali-Activated Binders for Use in Concrete
Provides guidance on materials, mix proportioning, and properties of alkali-activated binder concrete, similar to the IS code's guideline nature.
PAS 8820:2016British Standards Institution (BSI), UK
MediumWithdrawn
Alkali-activated cementitious material and concrete — Specification
Provided specifications for AAMs, whereas IS 17208 provides guidelines; however, the technical basis is highly comparable.
Z14/3:2017Concrete Institute of Australia (CIA), Australia
HighCurrent
Recommended Practice: Alkali-Activated Binders and Geopolymer Concrete
Offers recommendations on the use of alkali-activated materials, with a strong focus on geopolymer systems, mirroring the IS code's intent.
RILEM TC 247-DTARILEM (International Union of Laboratories and Experts in Construction Materials, Systems and Structures), International
HighCurrent
Recommendations for the mix design of alkali-activated materials
Provides expert recommendations for designing AAM mixes, focusing on the technical procedures that underpin guidelines like IS 17208.
Key Differences
≠IS 17208 uses the term 'Geopolymer Concrete' prominently, defining it as a specific subset of Alkali-Activated Materials (AAMs). Most international documents (e.g., ACI 236A, RILEM) prefer the broader, more inclusive term 'Alkali-Activated Material/Binder' to cover a wider range of precursors, including high-slag systems.
≠The Indian standard is heavily oriented towards the use of low-calcium (Class F) fly ash, reflecting its widespread availability in India. International guides like ACI 236A give more equal consideration to both fly ash-based and slag-based AAM systems.
≠IS 17208 places a strong emphasis on achieving adequate performance with ambient temperature curing (e.g., 27 ± 2 °C) to facilitate in-situ applications. Many international guides and early research placed greater emphasis on heat curing (60-80°C) to accelerate strength gain, especially for precast elements.
≠The IS code provides specific indicative ranges for mix design parameters like activator-to-binder ratio (0.35-0.55) and Na2SiO3/NaOH ratio (1.5-2.5). International guides like ACI 236A are often more principle-based, outlining the methodology for determining these ratios rather than prescribing narrow ranges.
Key Similarities
≈All standards are founded on the same chemical principle of using a highly alkaline solution (alkaline activator) to dissolve and repolymerize aluminosilicate source materials (precursors) like fly ash and GGBFS into a hardened binder.
≈There is a universal emphasis on a performance-based approach. All standards mandate trial mixing and testing to verify properties like workability, setting time, and strength, as the performance is highly dependent on the specific local source materials used.
≈All referenced standards highlight the critical importance of health and safety protocols when handling caustic alkaline activators (e.g., sodium hydroxide, sodium silicate), requiring stringent use of Personal Protective Equipment (PPE).
≈The fundamental material components are consistent across all standards: a solid precursor (primarily fly ash and/or GGBFS) and a liquid alkaline activator (typically a combination of sodium hydroxide and sodium silicate).
Parameter Comparison
Parameter
IS Value
International
Source
Primary Precursor Focus
Low-calcium (Class F) fly ash as per IS 3812 (Part 1).
Broader scope including both low-calcium fly ash and GGBFS.
ACI 236A-23
Standard Curing Condition
Ambient curing at 27 ± 2 °C and ≥ 90% RH.
Discusses both ambient and elevated temperature curing (e.g., 40-80°C), with heat curing common for precast.
ACI 236A-23
Typical Activator/Binder Ratio (by mass)
0.35 to 0.55
Generally in the range of 0.40 to 0.60, determined by trial mix to achieve desired workability.
RILEM TC 247-DTA
Typical Na2SiO3 / NaOH Ratio (by mass)
1.5 to 2.5
Often in the range of 1.0 to 3.0, selected to achieve a target silica modulus (Ms) in the activator.
RILEM TC 247-DTA
Compressive Strength Test Ages
Standard ages are 7 and 28 days.
Commonly 7 and 28 days, with 56 and 91 days also frequently specified to capture long-term strength development.
ACI 236A-23
RCPT Chloride Permeability Class ('Very Low')
< 1000 Coulombs (as per Annex C, informative).
< 1000 Coulombs, but notes that results can be misleading for AAMs due to pore solution conductivity.
ACI 236A-23 / ASTM C1202
⚠ Verify details from original standards before use
Key Values7
Quick Reference Values
Ratio of sodium silicate to sodium hydroxide solution1.5 to 2.5 by mass
Ratio of alkaline liquid to binder material0.4 to 0.55
Typical heat curing temperature60°C to 90°C
Typical heat curing duration6 to 48 hours
Rest period before heat curingMinimum 60 minutes
Maximum free water to binder ratio0.25
Fly Ash fineness (Retained on 45 micron IS Sieve)Max 20 percent
Tables & Referenced Sections
Key Tables
Table 1 - Requirements for Fly Ash for Geopolymer Concrete
Table 2 - Requirements for GGBS for Geopolymer Concrete
Table 3 - Suggested Molarity of Sodium Hydroxide Solution for Different Grades of Geopolymer Concrete
Table 4 - Recommended Requirements for Geopolymer Concrete for Durability
What are the main binders for GPC as per this code?+
Low-calcium (Class F) Fly Ash and/or Ground Granulated Blast-furnace Slag (GGBS) are the primary binders. (Clause 4)
What is the recommended ratio of sodium silicate to sodium hydroxide solution?+
A ratio between 1.5 to 2.5 by mass is generally recommended for achieving desirable workability and strength. (Clause 6.2.2)
Is heat curing mandatory for geopolymer concrete?+
No, but heat curing at 60-90°C is highly recommended to achieve higher early age strength. Ambient curing is also permitted but results in slower strength development. (Clause 9)
What molarity of NaOH is suggested for M30 grade GPC?+
A molarity of 10 M to 12 M is suggested for M30 grade concrete, but it should be finalized based on trial mixes. (Table 3)