During firing/heat-up, silica bricks exhibit a maximum linear expansion of approximately what percentage due to phase transformations?

Introduction / Context:
Silica bricks undergo polymorphic changes (e.g., quartz–tridymite–cristobalite) that cause dimensional changes on heating. Knowing the order of magnitude of linear expansion helps engineers allow for joints and avoid structural stress.

Given Data / Assumptions:

• We consider the net linear expansion during firing/heat-up into service ranges.
• Exact values depend on grade and schedule, but a typical maximum lies around the lower single-digit percent.

Concept / Approach:
Silica’s transformation-related expansion is notable but usually around ~1% in linear terms for many practical firing schedules, though some data may report slightly higher figures. For design allowances, the order of magnitude is closest to 1% among the options provided.

Step-by-Step Solution:
Recall silica exhibits expansion peaks tied to phase changes.Compare plausible percentages: 0.5% too low; 3.5–5% too high for typical linear expansion.Select the closest representative value: 1%.

Verification / Alternative check:
Handbooks list linear expansions of silica refractories roughly around the 1% range for practical temperature cycles.

Why Other Options Are Wrong:
2–5% substantially overstate typical linear expansion; 0.5% understates it.

Common Pitfalls:
Confusing linear expansion with volume expansion; volumetric numbers are roughly three times linear values.

Final Answer:
1