Silica (SiO2) refractories: Which property most directly indicates the degree of firing/vitrification achieved in a silica brick during manufacture?

Introduction / Context:
Quality control of silica bricks relies on markers that reflect the extent of firing, phase transformation, and vitrification. While several properties are measured, not all directly reveal the degree of firing attained during manufacture.

Given Data / Assumptions:

• Silica brick develops different SiO2 polymorphs (quartz, tridymite, cristobalite) as firing progresses.
• Manufacturing aims to achieve controlled conversion and vitrification for dimensional stability and performance.
• We compare specific gravity, fusion point, and RUL as indicators.

Concept / Approach:
Specific gravity (true density) of silica brick correlates with mineralogical conversion and degree of vitrification. Fusion point is an inherent high-temperature property that does not vary sensitively with small changes in firing extent. RUL measures performance under load at high temperature but is influenced by porosity, microstructure, and impurities, not solely the degree of firing.

Step-by-Step Solution:

Verification / Alternative check:
Materials practice correlates true specific gravity with phase analysis (e.g., XRD) to audit firing consistency in silica refractories.

Why Other Options Are Wrong:

• Fusion point: Too insensitive to incremental firing differences.
• RUL: Performance metric under load; not a direct indicator of firing extent.
• None of these: Incorrect because specific gravity is a valid indicator.

Common Pitfalls:
Equating high RUL with high firing—RUL can improve via composition or grain size control without strictly reflecting firing degree.

Final Answer:
specific gravity