Fire resistance of building stones: select the correct set of statements about mineral changes and stone types under heating. Choose the most comprehensive correct option.
-
AFree quartz shows a sudden expansion near 573°C (below 600°C) due to the alpha–beta transition
-
BLimestone resists fire up to about 800°C; at higher temperature it decomposes into CaO and CO2
-
CSiliceous sandstones resist fire relatively better than many other stones
-
DArgillaceous stones (clay-rich) are comparatively poorer in strength but can resist fire fairly well
-
EAll the above
Answer
Correct Answer: All the above
Explanation
Introduction / Context:Understanding stone behavior in fire helps engineers select facing and structural masonry where thermal shock and decomposition are concerns. This question ties mineral transformations to practical fire performance of common stones.
Given Data / Assumptions:
- Quartz undergoes a known phase transition near 573°C causing volume change.
- Limestone decomposes on strong heating, affecting integrity.
- Siliceous vs argillaceous compositions influence fire resistance differently.
Concept / Approach:
Mineralogy governs thermal stability. Quartz-bearing stones may experience internal stress near the 573°C transition, but siliceous sandstones generally remain more fire-resistant than calcareous stones that calcine. Argillaceous stones, though weaker mechanically, often show better resistance to fire damage than limestones because they lack the calcination decomposition that generates CO2 and disrupts the matrix.
Step-by-Step Solution:
Confirm a): quartz transition and expansion below 600°C.Confirm b): limestone calcination → CaO + CO2 above ~800–900°C.Confirm c): siliceous sandstones generally outperform in fire compared with limestones.Confirm d): argillaceous stones can resist fire fairly well despite lower strength.Verification / Alternative check:
Fire test data and manuals consistently warn of limestone spalling due to calcination; quartz transition is a standard property, and clays/silicates manage heat differently.
Why Other Options Are Wrong:
Choosing anything less than “All the above” omits one or more true statements.
Common Pitfalls:
Assuming highest compressive strength equals best fire resistance; overlooking chemical decomposition under heat.
Final Answer:
All the above