For standard fireclay (firebrick) compositions, the silica (SiO2) percentage is typically about which of the following ranges?

Introduction / Context:
Fireclay bricks are alumino-silicate refractories used widely in industry. Knowing their typical SiO2 content aids in matching them to acid/basic environments and predicting corrosion behavior.

Given Data / Assumptions:

• Fireclay bricks usually contain both Al2O3 and SiO2.
• Typical dense grades cluster around ~55–60% SiO2 and ~30–40% Al2O3.

Concept / Approach:
The common specification range for standard fireclay places silica around the mid-50s percentage. Lower numbers suggest high-alumina grades; very high numbers (80%+) indicate silica or semi-silica bricks, not standard fireclay.

Step-by-Step Solution:
Eliminate extremes: >94 or 80–85 represent high-silica categories.35–40 is too low for typical fireclay.Select ~55–60 as representative.

Verification / Alternative check:
Supplier datasheets and handbooks list fireclay compositions consistent with this band.

Why Other Options Are Wrong:
Very high or very low SiO2 ranges correspond to different refractory families.

Common Pitfalls:
Confusing fireclay with either high-alumina or high-silica products.

Final Answer:
55–60