ISO 22904:2020

Overview

ISO 22904:2020 - Additions for concrete specifies requirements for three common Type II additions used in concrete production: silica fume, siliceous fly ash, and ground granulated blastfurnace slag (GGBFS). The standard sets out the properties, testing and conformity requirements these additions must meet when used in concrete that conforms to ISO 22965. Additions covered may also be used in mortars and grouts. ISO 22904:2020 clarifies what is in scope (by‑product silica fume from silicon/ferro‑silicon smelting, specific fly ashes, and GGBFS without added materials) and what is excluded (certain co‑combustion ashes, slag with added constituents, and practical application processes such as mixing or curing).

Key Topics and Technical Requirements

• Material definitions and classification: clear definitions for silica fume, fly ash and ground granulated blastfurnace slag including processing states (densified, slurry).
• Chemical requirements: compositional limits and test methods for relevant chemical constituents (references to standardized analysis methods such as ISO 29581 and ICP‑OES where applicable).
• Physical requirements: particle characteristics, fineness/surface area (e.g., BET method ISO 9277), bulk and particle density, moisture content (see normative Annex A for GGBFS moisture).
• Durability and safety: durability-related criteria, release of dangerous substances and radioactivity limits.
• Sampling, conformity and quality control: prescribed sampling procedures, conformity assessment and evaluation (informative guidance in Annex D).
• Normative test methods: several annexes provide methods (moisture content, water requirement for specific fly ash categories, soluble phosphate determination).
• Packaging, labelling and marking: requirements to ensure traceability and user information.

Note: ISO 22904 does not prescribe how to use these additions in concrete mixes (batching, placing, curing); users should consult ISO 22965‑2 for suitability, batching, k‑value concept and practical guidance.

Practical Applications and Who Uses This Standard

• Concrete producers and ready‑mix plants selecting and specifying Type II additions to achieve targeted fresh and hardened concrete performance.
• Material suppliers and processors ensuring silica fume, fly ash or GGBFS meet international quality and conformity requirements.
• Testing laboratories and QA/QC teams performing chemical and physical testing, sampling and conformity evaluation.
• Specifiers, engineers and consultants referencing ISO 22904 when writing material specifications for durable, sustainable concrete (including use in mortars and grouts).

Related Standards

• ISO 22965‑2 (concrete constituent specification and use)
• ISO 9277 (BET surface area), ISO 29581 (chemical analysis), ISO 11885 (ICP‑OES)
• Relevant EN standards cited in the document for cement and fly ash test methods

Keywords: ISO 22904:2020, additions for concrete, silica fume standard, fly ash specification, ground granulated blastfurnace slag, GGBFS, Type II addition, ISO 22965.