Typical apparent porosity band for dense fireclay refractories falls within which percentage range?

Introduction / Context:
Apparent porosity influences heat flow, corrosion resistance, and mechanical strength. For dense (non-insulating) fireclay bricks, there is a characteristic porosity window that balances properties and cost.

Given Data / Assumptions:

• Densely fired fireclay, not insulating firebrick.
• Pressed or extruded and fired under conventional schedules.
• Typical values requested.

Concept / Approach:
Dense fireclay products commonly show apparent porosity between 25 and 35 percent. Lower than ~10–15 percent is unusual for standard grades, while > 50–60 percent indicates insulating bricks rather than dense structural fireclay.

Step-by-Step Solution:
Exclude very low values typical of special high-density products.Exclude very high values typical of insulating firebrick.Choose 25–35 percent as the representative band.

Verification / Alternative check:
Reference data sheets for general-purpose fireclay list porosity in the mid-20s to low-30s percent.

Why Other Options Are Wrong:
5–10 or 10–25: typically too low for common dense grades.35–50 or over 60: trending toward insulating categories or special porosity designs.

Common Pitfalls:
Mixing values for dense bricks with those for insulating firebrick (which are deliberately porous).

Final Answer:
25–35 percent