Refractoriness under load (RUL) versus fusion temperature (PCE): for which brick type are these two temperatures typically closest in value during testing?

Introduction / Context:
Refractoriness under load (RUL) measures the temperature at which a refractory deforms under a specified load, while the pyrometric cone equivalent (PCE) reflects softening/fusion in a standardized cone test. The relationship between RUL and PCE depends on the bonding and phase-transformation behavior of the refractory.

Given Data / Assumptions:

• We compare typical behavior of common brick families.
• Testing uses standard loads and heating rates.
• We want the family where RUL ≈ PCE most closely.

Concept / Approach:
Silica bricks (high SiO2) exhibit strong high-temperature stability once above inversion ranges, and their load-bearing capacity persists up to temperatures close to their fusion softening, yielding RUL values close to PCE. Fireclay and low-alumina bricks often have glassy phases that soften earlier under load, so their RUL is appreciably lower than PCE. Basic bricks (e.g., dolomite) show different hot strength behavior and do not generally display the same close correspondence as silica bricks.

Step-by-Step Solution:
Recall silica brick features: high softening range and strong load-bearing at high T.Contrast with fireclay: earlier softening due to glassy phase → lower RUL vs PCE.Eliminate others (dolomite/very low alumina) based on typical hot strength curves.Select silica bricks.

Verification / Alternative check:
Materials handbooks chart silica bricks with RUL temperatures near their PCE, whereas fireclay bricks show larger separations.

Why Other Options Are Wrong:
Fireclay/very low alumina: higher glassy content lowers RUL relative to PCE.Dolomite: basic, with different deformation behavior; not closest.

Common Pitfalls:
Equating PCE with service temperature limits; RUL is more indicative of load-bearing performance under actual furnace stresses.

Final Answer:
Silica bricks