Apparent porosity range of standard silica bricks typically falls in which percentage band?

Introduction / Context:
Apparent porosity affects thermal conductivity, corrosion resistance, and strength. For silica bricks used in crowns and high-temperature structures, porosity is controlled within a characteristic range.

Given Data / Assumptions:

• Standard dense silica bricks, not insulating types.
• Typical manufacturing routes (pressed, fired).
• We seek the common specification band.

Concept / Approach:
Silica bricks generally exhibit apparent porosity around 20–30 percent, balancing strength with acceptable thermal properties. Much higher porosity levels are characteristic of insulating bricks; much lower values are unusual for standard dense silica products.

Step-by-Step Solution:
Exclude very low porosity bands (e.g., 5–10%).Exclude very high porosity typical of IFB (45–75%).Select 20–30 percent as the standard band.

Verification / Alternative check:
Supplier datasheets and handbooks cite porosity values most often in the 20–30 percent range for dense silica bricks.

Why Other Options Are Wrong:
5–10 or below 3: too low for typical dense silica.45–75: far too high; typical of insulating grades, not dense bricks.

Common Pitfalls:
Confusing dense bricks with insulating silica bricks designed for low conductivity.

Final Answer:
20–30 percent