The determination of linear thermal expansion (LTE) and of the thermal expansion curve of a refractory material is of great importance in assessing its dimensional behaviour during the heating up (or cooling down) phase, and therefore is fundamental for the correct design of expansion joints and tolerances.

In particular, it is particularly critical when in the material there are phases that undergo crystallographic transformations accompanied by sudden changes in volume, as in the case of the zirconium oxide present in AZS fused-cast refractories (melting tank and superstructure) or in silica bricks (crown).

The measurement is made by subjecting a sample of standard shape and size to a slow and progressive heating, determining the resulting deformation (expansion or contraction) as a function of temperature under conditions of minimum axial load both on RUL/Creep tester (ASTM C832, UNI EN 993-19, ISO 16835) and on pushrod dilatometer (ISO 16835).