Refractory and silica bricks – composition, absorption, and strength facts Which of the following statements about firebricks and silica bricks are correct in traditional specifications?
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AWater absorption of firebricks is typically about 5% to 10%
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BSilica bricks contain about 95% to 97% silica by composition
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CAbout 1% to 2% lime is added to silica bricks as a binding material
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DCompressive strength of silica bricks is approximately 150 kg/cm^2
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EAll of the above
Answer
Correct Answer: All of the above
Explanation
Introduction / Context:Refractory materials such as firebricks and silica bricks are essential for high-temperature structures including furnaces, kilns, and chimneys. Understanding their key properties—water absorption, chemical composition, and compressive strength—enables appropriate selection and specification for thermal and mechanical performance in service.
Given Data / Assumptions:
- Traditional values from building-materials references are considered.
- Ranges are indicative, acknowledging manufacturer and test variability.
- We focus on the correctness of each statement as a typical benchmark.
Concept / Approach:
Firebricks are designed to withstand high temperatures and thermal cycling; their absorption usually lies within controlled limits (about 5%–10%) to minimize spalling. Silica bricks are characterized by very high silica content (around 95%–97%) with minor additions—commonly lime (about 1%–2%)—to aid bonding and sintering. Their compressive strength values are moderate compared with structural stones or concretes but adequate for refractory linings, often quoted around 150 kg/cm^2 in exam-oriented data sets.
Step-by-Step Solution:
1) Absorption check: firebricks 5%–10% is a commonly cited target range.2) Composition: silica bricks 95%–97% silica is a hallmark.3) Binder: lime addition about 1%–2% is standard for bonding in silica bricks.4) Strength: compressive strength ~150 kg/cm^2 appears in classic materials tables.5) Therefore, all statements align with traditional specifications.Verification / Alternative check:
Multiple handbooks on refractory bricks corroborate these indicative ranges, noting that precise values vary with formulation and firing schedules.
Why Other Options Are Wrong:
Each individual statement stands on its own; hence the combined option is correct.
Common Pitfalls:
Expecting structural-level compressive strengths from refractories; assuming zero water absorption; ignoring that small lime additions serve as binders in silica compositions.
Final Answer:
All of the above