Why are magnesite refractory bricks susceptible to hydration caused by moisture? What precautions should be taken during storage and transportation?
Sep 15,2026
I. Core Principle: Why are magnesia bricks susceptible to water?
For all magnesia-based basic refractory bricks—such as magnesia-iron spinel bricks and magnesia-alumina spinel bricks—the core component of the matrix is periclase (MgO), which undergoes an irreversible hydration reaction upon contact with water:
🧪 MgO + H₂O → Mg(OH)₂
⚠️ Volume expands by approximately 120%
Hydration occurs not only on the surface but also penetrates the brick's interior, causing two types of damage:
- 🔬 Latent Cracks: Internal expansion stress leads to micro-cracks, bulging, and structural loosening—defects that are difficult to detect with the naked eye in the early stages.
- 🔥 Kiln Failure: During the kiln heat-up process, hydration products dehydrate and release gas, causing cracks to propagate and leading to spalling, brick detachment, and localized overheating ("red spots").
> 📌 Key Note: Spinel bricks are not immune to water; they merely possess slightly better water resistance and still carry a risk of hydration. In contrast, silicon-mullite bricks and alkali-resistant high-alumina bricks generally do not pose a hydration risk.
II. High-Risk Scenarios for Moisture Exposure
The following scenarios are most likely to cause moisture absorption and hydration in magnesia bricks:
- 🌧️ Outdoor handling during the rainy season: Transport or installation during rain or heavy fog
- 🏢 Damp warehouse conditions: Rising damp from the floor, wall seepage, or poor ventilation
- 📦 Damaged packaging: Torn waterproof film allowing moisture to penetrate the brick stack
- 🚢 Condensation during ocean shipping: Significant temperature fluctuations inside shipping containers leading to "container rain"
- ⏳ Prolonged storage: Excessive inventory time or prolonged exposure after unpacking
III. Moisture Protection Standards for Transport
To mitigate the risk of hydration, strict protective measures must be implemented during transport:
- 📦 Sealed Packaging: Full wrapping with stretch film and PE waterproof film; inclusion of desiccant for export orders.
- 🚛 Vehicle Protection: Pre-inspection of truck beds and containers to ensure they are dry and leak-free; moisture-proof sheeting laid on the floor.
- ⚠️ Operational Control: Loading and unloading in the open air is prohibited during rain, snow, or fog; damaged packaging must be isolated separately.
- 🚢 Enhanced Sea Freight Measures: Vacuum-sealed wrapping to minimize moisture damage caused by condensation resulting from temperature fluctuations.
IV. Storage and Preservation Guidelines
Proper storage is critical for protecting magnesia bricks from moisture:
- 🏭 Indoor Storage: Outdoor stacking is prohibited; bricks must be stored in a dry warehouse.
- 📏 Elevation and Clearance: Stack bricks at least 15 cm off the ground and 30 cm away from walls.
- 💨 Ventilation and Humidity Control: Maintain warehouse ventilation and keep humidity below 70% whenever possible.
- 🔄 First-In, First-Out (FIFO): Use within 6 months of production; avoid long-term stockpiling.
- 📤 Unwrap Before Use: Remove the waterproof wrapping only before laying the bricks; re-cover and seal them during work stoppages.
V. Inspection upon Delivery: How to Detect Hydration?
Pay close attention to the following characteristics upon delivery:
- ❌ Abnormal appearance: White powdery efflorescence on the surface, bulging edges/corners, or hairline cracks
- ❌ Abnormal sound: A dull or muffled sound when tapped
- ✅ Normal state: Dry brick body, intact appearance, and a crisp sound when tapped
> 🚫 Conclusion: Bricks suspected of hydration—or showing signs of mild hydration—are strictly prohibited from use in the kiln.
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