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IS 12679:1989 is the Indian Standard (BIS) for by-product gypsum for use in plaster, blocks and boards. This standard lays down the requirements for by-product gypsum, such as phosphogypsum and fluoro-gypsum, intended for use in the manufacture of building materials like plasters, blocks, and boards. It specifies the necessary chemical composition and physical properties to ensure the quality and performance of the final products.
By-product gypsum for use in plaster, blocks and boards
Overview
Status
Current
Usage level
Specialized
Domain
Materials Science — Building Limes and Gypsum Products
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! By-product gypsum originates from industrial processes (e.g., fertilizer plants, power plants), so its impurity profile can vary. Testing against Table 1 for contaminants like chlorides and fluorides is critical.
! The setting time requirements (20 min initial, 30 min final) are for the raw gypsum material itself, not the final plaster product, which will have retarders added to extend working time.
! This gypsum is primarily used for non-structural interior applications like partition walls and false ceilings.
Covers specifications for natural and by-product (synthetic) gypsum for manufacturing gypsum products.
EN 13279-1:2008CEN (European Committee for Standardization), Europe
HighCurrent
Gypsum binders and gypsum plasters - Part 1: Definitions and requirements
Specifies requirements for gypsum binders, including synthetic types, for use in construction.
ASTM C1658 / C1658M - 19ASTM International, USA
HighCurrent
Standard Specification for Mechanical-Grade, Synthetic Gypsum Used for Manufacturing Gypsum Panel Products
Specifically covers by-product (synthetic) gypsum for the manufacture of gypsum panels/boards.
GB/T 36141-2018SAC (Standardization Administration of China), China
MediumCurrent
Desulfurized gypsum
Specifies requirements solely for flue gas desulfurization (FGD) gypsum, a major type of by-product gypsum.
Key Differences
≠IS 12679 includes an explicit maximum limit for radioactivity (Radium-226 at 925 Bq/kg), a concern for phosphogypsum. Most ASTM and EN standards do not specify this, deferring to broader national environmental and health regulations.
≠The Indian standard is prescriptive, setting specific chemical limits for impurities like phosphates (P₂O₅) and fluorides (F). In contrast, EN 13279-1 is more performance-based, controlling such impurities indirectly through their effect on setting time and strength.
≠IS 12679 provides a single set of requirements for all by-product gypsum. International practice often involves more specific standards for different types, such as ASTM C1658 for gypsum for panels or GB/T 36141 for FGD gypsum, which have tailored requirements.
≠EN 13279-1 provides a detailed classification system for gypsum binders (e.g., A1, B1-B7, C1-C7) based on use, manufacturing process, and properties. IS 12679 does not classify the raw by-product gypsum.
Key Similarities
≈All standards define the primary material as hydrated calcium sulfate (CaSO₄·2H₂O) and specify a minimum purity level, forming the basis for its suitability.
≈The intended application is consistent across all standards: the use of by-product gypsum as a raw material for manufacturing building materials like plaster, blocks, and boards.
≈All standards specify controls on physical properties crucial for processing, such as fineness (particle size distribution) and free water content.
≈There is a common understanding of the need to limit certain chemical impurities, like chlorides, which are known to affect setting behavior and can cause efflorescence or corrosion.
Parameter Comparison
Parameter
IS Value
International
Source
Purity (CaSO₄·2H₂O Content)
Min 90.0% by mass
Min 94.0% by mass
ASTM C1658 / C1658M
Free Water Content
Max 20.0% by mass
Max 15.0% by mass
ASTM C1658 / C1658M
pH of Aqueous Extract
Min 5.0
4.5 to 9.0
ASTM C1658 / C1658M
Fineness (Retained on Sieve)
Max 1.0% on 2.0 mm sieve
Max 1.0% on 1.18 mm sieve
ASTM C22 / C22M
Chlorides (as Cl⁻)
Max 0.1% (1000 ppm)
Max 0.025% (250 ppm)
ASTM C1658 / C1658M
Soluble Phosphates (as P₂O₅)
Max 0.1%
Not explicitly specified; controlled by performance tests (e.g., setting time).
EN 13279-1
Radioactivity (Radium-226)
Max 925 Bq/kg
Not specified in the standard; governed by separate national regulations.
ASTM C22 / C22M
⚠ Verify details from original standards before use
Key Values6
Quick Reference Values
Minimum Calcium Sulphate (CaSO₄·2H₂O) content85.0 % by mass
Maximum Chloride (as Cl) content0.1 % by mass
Maximum Fluoride (as F) content1.0 % by mass
Fineness (residue on 150-micron sieve)5.0 % by mass max
Initial Setting Time20 minutes min
Final Setting Time30 minutes max
Tables & Referenced Sections
Key Tables
Table 1 - Chemical Requirements for By-Product Gypsum
Table 2 - Physical Requirements for By-Product Gypsum