ISO 3262-21:2023

Overview

ISO 3262-21:2023 - "Extenders - Specifications and methods of test - Part 21: Silica sand (unground natural quartz)" specifies requirements and test methods for silica sand (unground natural quartz) used as an extender/filler. The standard defines grades, essential and conditional characteristics, sampling rules and a laboratory method to determine silica content. It replaces ISO 3262-21:2000 and aligns silica sand testing with the ISO 3262 series for extenders.

Key topics and technical requirements

• Scope: Requirements and corresponding test methods for unground natural quartz (silica sand).
• Grades & limits: Essential characteristics include:
  • Quartz content (XRD): Grade A min 99% - Grade B min 80%
  • Silica content (XRF or Clause 6 method): Grade A min 97% - Grade B min 80%
  • Matter volatile at 105 °C (ISO 787-2): max 0.5% mass fraction
  • Loss on ignition (ISO 3262-1): Grade A max 0.4% - Grade B max 2.5%
  • Matter soluble in water (ISO 787-3): Grade A max 0.2% - Grade B max 0.6%
  • pH of aqueous suspension (ISO 787-9): specified ranges per grade
• Silica content determination (Clause 6):
  • Principle: ignition, treatment with sulfuric and hydrofluoric acids, evaporation of silicon tetrafluoride and mass loss measurement.
  • Key apparatus: platinum dish, muffle furnace (1 000 ± 20 °C), hotplate, desiccator, analytical balance (0.0001 g).
  • Procedure: duplicate determinations on ~2 g test portions, specified acid treatments and ignition steps; mean result reported to 0.1% mass.
• Sampling: Representative sampling in accordance with ISO 15528.
• Reporting: Test report must identify the product, reference ISO 3262-21:2023, list results, methods, deviations and test dates.

Applications and who uses it

• Manufacturers and suppliers of silica sand extenders/fillers
• Quality control and analytical laboratories testing silica content, loss on ignition and impurities
• Paints, coatings and plastics raw materials procurement and R&D teams specifying filler performance
• Standards bodies, regulators and conformity assessment organizations referencing consistent test methods

Related standards

• ISO 3262-1 (Introduction and general test methods)
• ISO 787 series (Parts 2, 3, 7, 9, 14) - general test methods for pigments and extenders
• ISO 15528 (Sampling for paints and raw materials)
• ISO 3696 (Laboratory water quality)
• ISO 18451-1 (Terminology)
• Other parts of the ISO 3262 series

Keywords: ISO 3262-21:2023, silica sand specification, unground natural quartz, extenders, silica content determination, X-ray fluorescence, X-ray diffraction, loss on ignition, sampling, test methods.