ASTM C1240

Silica Fume Used in Cementitious Mixtures

Applicability: Covers silica fume used as a supplementary cementitious material in concrete and other systems containing hydraulic cement. Applies to raw silica fume as well as slurried or densified forms; densified products must be tested in their raw state for specification compliance. The standard applies to all amorphous silica materials regardless of particle morphology, with SI units as the standard system.

Purpose: Establishes minimum chemical, physical, and performance requirements for silica fume, including limits on SiO₂ content, loss on ignition, moisture content, oversize material, specific surface area (BET nitrogen adsorption), and strength activity index. Testing verifies that silica fume contributes positively to concrete strength and durability without increasing alkali-silica reaction risk. Results are used to qualify material for high-performance concrete, bridge decks, and structures requiring reduced permeability.