Effect of porosity on properties: as apparent porosity decreases in a refractory brick, which property typically decreases (rather than increases)?

Introduction / Context:
Porosity influences thermal, mechanical, and durability properties. Engineers must know which traits improve or worsen as porosity changes to optimize lining life for a given service environment.

Given Data / Assumptions:

• “Porosity” refers to apparent porosity in fired refractories.
• Lower porosity usually means higher strength and greater thermal conductivity.
• Thermal-shock (spalling) resistance often benefits from some compliant microstructure.

Concept / Approach:
Reducing porosity densifies the brick, increasing mechanical strength and thermal conductivity. However, thermal-shock resistance typically decreases because a denser, stiffer structure cannot absorb thermal strains as effectively. Microcrack networks and controlled pores dissipate stress and delay crack propagation, so less porosity can mean lower spalling resistance.

Step-by-Step Solution:
Relate porosity ↓ to density ↑ and strength ↑.Recognize thermal conductivity tends to increase as solid pathways improve.Identify the property likely to decrease: spalling resistance.

Verification / Alternative check:
Thermal shock indices often improve with controlled porosity and microcracking; dense bricks are more crack-prone on sudden quench.

Why Other Options Are Wrong:
Strength/Thermal conductivity: generally increase when porosity decreases.“None of these”: incorrect, as spalling resistance usually declines.

Common Pitfalls:
Assuming “denser is always better”; application dictates the needed porosity balance.

Final Answer:
Spalling resistance