Compared with ordinary fireclay bricks, high-alumina refractories generally exhibit which of the following performance characteristics?

Introduction / Context:
As alumina content increases from fireclay grades (~30–45% Al2O3) to high-alumina bricks (50–90% Al2O3), the phase assemblage shifts toward mullite and corundum, improving hot properties. Understanding these trends enables appropriate brick selection for severe service zones. This question asks which statement best captures the general performance of high-alumina refractories versus fireclay.

Given Data / Assumptions:

• High-alumina bricks target higher softening temperatures and better corrosion resistance.
• Thermal-shock resistance can vary by grade and porosity but is commonly improved in engineered high-alumina products.
• Creep resistance at service temperature typically increases with alumina content and reduced glassy phase.

Concept / Approach:
High-alumina compositions reduce the low-melting glassy phase present in fireclays and develop stronger mullite/corundum networks. The result is higher refractoriness, better hot modulus of rupture, improved RUL, better slag resistance in many environments, and enhanced creep resistance. Many modern high-alumina bricks are engineered for better thermal-shock resistance through controlled porosity and microcracking strategies, making the combined statement in option (d) the best comparative description among those listed.

Step-by-Step Solution:
Compare phases: fireclay (glassy) vs. high-alumina (mullite/corundum).Relate phases to properties: higher Al2O3 → higher refractoriness and hot strength.Assess creep and thermal shock: improved by phase stability and design features.Select option summarizing these improvements: (d).

Verification / Alternative check:
Datasheets for high-alumina bricks show higher RUL, HMOR, and lower creep than general-purpose fireclays; application notes also highlight enhanced thermal-shock performance in certain high-alumina lines.

Why Other Options Are Wrong:
(a) Less load-bearing: opposite of observed behavior.(b) Less slag resistance: generally false; high-alumina resists many slags better.(c) Low refractoriness: contradicts the definition of high-alumina.(e) Lower RUL: high-alumina typically has higher, not lower, RUL.

Common Pitfalls:
Assuming all high-alumina brick types share identical shock resistance; formulation matters.Ignoring service-specific slag chemistry where silica-rich bricks might occasionally fare better.

Final Answer:
High resistance to thermal shock and creep