Overview
ISO 22685:2021 specifies a standardized test method for determining the compressive strength of refractory products at elevated temperature. The method defines specimen preparation, furnace and loading apparatus requirements, measurement and calculation procedures, and reporting. It is intended for materials development, quality control, characterization, design data generation and can be adapted for carbon-containing refractories tested in an airtight furnace with a reducing atmosphere.
Key topics and technical requirements
- Test principle: Apply an increasing compressive load at a specified elevated temperature until failure (fracture or defined strain limits) and calculate compressive strength from maximum load divided by specimen cross-sectional area.
- Specimen dimensions: Preferred cylinders 50 mm ± 0.5 mm height and 50 mm ± 0.5 mm diameter; alternate cubes 40 mm ± 0.5 mm when cylinders are impractical. Minimum three specimens recommended.
- Failure/strain criteria: Dense refractories - failure or strain reaching 1% ; shaped insulating refractories - failure or strain reaching 10%.
- Furnace and temperature control: Furnace must maintain constant heating rate; temperature deviation shall be less than 20 °C when test temperature is above 500 °C. Thermocouple hot junction should be within 10 mm of specimen center.
- Loading machine and measurement accuracy: Machine capacity greater than 10% of expected fracture load; load measurement accuracy within 2%. Deformation measuring device sensitivity better than 0.005 mm; calipers capable to 0.1 mm.
- Apparatus details: Requirements for loading/support columns, refractory discs between columns and specimen, and drying oven (110 °C ± 5 °C) are included.
- Sampling and preparation: Sampling aligned with ISO 5022 (shaped) and ISO 1927 series (unshaped); orientation of test pieces relative to manufacture forming pressure should be recorded.
Applications and users
ISO 22685:2021 is used for:
- Quality control and batch acceptance testing of refractory bricks and monolithics.
- Materials development and R&D to compare high-temperature mechanical performance.
- Design and engineering to generate reliable mechanical data for lining selection and thermal-mechanical modeling.
Primary users include refractory manufacturers, materials testing laboratories, metallurgical and process-plant engineers, and R&D teams concerned with high-temperature structural properties.
Related standards
- ISO 5022 - Shaped refractory products: sampling and acceptance testing
- ISO 1927-2 / ISO 1927-5 - Monolithic refractory products: sampling and specimen preparation/treatment
- ISO 8895 - Cold crushing strength for shaped insulating refractories
- ISO 10059-1 - Cold compressive strength for dense shaped refractories
Keywords: ISO 22685:2021, refractory products, compressive strength at elevated temperature, high-temperature testing, quality control, refractory testing method.