Overview
ISO 8840:2021 - Refractory materials - Determination of bulk density of granular materials (grain density) specifies standardized methods to determine the bulk (grain) density of granular refractory materials with grain size larger than 2 mm. The standard defines three measurement methods (mercury displacement under vacuum, arrested water absorption, and a vacuum method with spin-dryer option per ISO 5017), explains sampling and sample preparation, and gives procedures for calculating and reporting results. Method 1 (mercury with vacuum) is the reference method; however, because mercury is hazardous, the standard recommends Method 2 for routine use.
Key topics and technical requirements
- Scope and definition: Grain density = mass of a quantity of material divided by the total volume of its grains, including closed pores.
- Measurement principle: Volume measurement by liquid displacement (mercury or water) to calculate bulk density (mass/volume).
- Three prescribed methods:
- Method 1 - Mercury method with vacuum: Reference method; requires vacuum (residual pressure < 3 000 Pa, preferably 133 Pa) and a vacuum pycnometer arrangement. Mercury density temperature corrections are specified.
- Method 2 - Arrested water absorption method: Recommended for routine testing (avoids mercury hazards).
- Method 3 - Vacuum method with spin dryer option: Based on ISO 5017; added in this edition, aligned with EN 993‑18.
- Sampling and sample prep: Follow ISO 8656 or agreed schemes. Remove dust, sieve to fractions > 2 mm; recommended narrowing to 3–4 mm for reproducibility.
- Sample size, drying and weighing:
- Use at least three test samples from the laboratory sample.
- Dry test samples to constant mass at 110 ± 5 °C; cool in a desiccator.
- Weigh to nearest 0.1 g with scale graduation 0.01 g.
- Recommended test-sample masses depend on grain size and homogeneity (examples in the standard).
- Reporting: Because methods can yield different values for some materials, always state the method used when reporting bulk density.
Applications and users
ISO 8840:2021 is used by:
- Refractory manufacturers and quality laboratories for material characterization and quality control.
- Research labs and material testing services assessing grain density, porosity implications, and mix design.
- Plant engineers and process designers who need accurate refractory material properties for selection and performance prediction.
Practical applications include product specification, acceptance testing, material selection for high-temperature linings, and interlaboratory comparisons.
Related standards
- ISO 5017 - Dense shaped refractory products (used for Method 3)
- ISO 8656 - Sampling of refractory raw and unshaped products
- ISO 383, ISO 385-1 - Laboratory glassware references cited in procedures
Keywords: ISO 8840:2021, refractory materials, bulk density, grain density, mercury method, arrested water absorption, vacuum method, ISO 5017, sample preparation, refractory testing.