Overview
ISO 16835:2014 specifies test methods for determining the thermal expansion behaviour of refractory products. The standard defines how to measure the linear thermal expansion percentage, the linear thermal expansion curve (rising and declining), and the linear thermal expansion coefficient. It covers three validated measurement approaches:
- Contact method with a cylindrical test piece,
- Contact method with a rod test piece, and
- Non-contact method.
The standard describes required apparatus, test-piece geometry, heating-furnace conditions, measurement detectors and procedures, calculations and plotting of results, and reporting requirements.
Key Topics and Requirements
- Scope and purpose: Measurement of dimensional change vs temperature for refractory materials to quantify expansion and derive coefficients used in design and QA.
- Three test methods: Two contact-based (cylindrical and rod specimens) that employ contact detectors and spacers, and one non-contact optical or displacement method - each method’s characteristics are compared in Annex A.
- Apparatus and setup: Specifications and alignment for pressure rods, supporting rods, disk-type spacers, alumina detection tubes, thermocouples and a tubular heating furnace with a controlled, uniform heating zone. Contact method designs include measures to avoid chemical reaction (e.g., platinum foil between specimen and spacers).
- Measurement outputs: Linear thermal expansion percentage (E), linear thermal expansion curve (rising and declining), average and instantaneous coefficients of linear thermal expansion (α), and difference of elongation against a reference sample.
- Procedure and calculation: Stepwise heating at specified rates, continuous or episodic displacement measurement, calibration against reference samples, and standardized calculation/drawing of expansion curves.
- Test reporting: Requirements for documenting apparatus, sample geometry, temperatures (T0, T1, T2), measured curves, coefficients and any deviations from the method.
Practical Applications and Who Uses It
ISO 16835 is essential for:
- Refractory manufacturers and quality-control laboratories - to verify product compliance and batch consistency.
- Materials and R&D teams - to characterise new compositions and predict thermal behaviour.
- Designers/engineers of high-temperature installations (furnaces, kilns, metallurgical vessels) - to select refractories and evaluate thermal stress and dimensional stability.
- Third‑party test houses and procurement/spec writers - to specify reproducible test methods in contracts and standards.
Typical uses include product specification, selection, failure analysis, thermal stress modelling, and certification testing.
Related Standards
Normative references in ISO 16835 include ISO 836 (Terminology for refractories) and IEC 60584 (thermocouples - reference tables and tolerances). Annexes provide method characteristics, recommended reference-sample values, and an example non-contact apparatus. Keywords: ISO 16835, refractory testing, thermal expansion, linear thermal expansion coefficient, contact method, non-contact method.
