🏗️ Le Chatelier Soundness Test of Cement
📘 Aim
To determine the soundness of cement by the Le Chatelier method as per IS: 4031 (Part 3) – 1988.
🔍 Purpose
The soundness of cement represents its ability to retain volume after setting without delayed expansion. Excessive expansion may occur due to the presence of free lime (CaO) or magnesia (MgO). This can cause cracks and disintegration in hardened concrete. The Le Chatelier Test is used to measure such expansion under normal atmospheric pressure.
⚙️ Apparatus Required
- Le Chatelier mould (split cylinder with indicator arms)
- Glass plates (for placing the mould)
- Trowel
- Balance (accuracy ±1 g)
- Water bath (for boiling water)
- Vernier caliper or scale (accuracy 0.1 mm)
🧱 Test Sample Preparation
- Prepare a neat cement paste of standard consistency.
- Lightly oil the Le Chatelier mould and glass plates.
- Fill the mould with cement paste and cover it with another glass plate.
- Place a small weight on top to ensure uniform thickness.
🧪 Procedure
- Store the filled mould in a moist environment for 24 hours at 27 ± 2°C and 90% humidity.
- Measure the initial distance (A₁) between the indicator points.
- Immerse the mould in water at room temperature and gradually bring it to boiling within 25 to 30 minutes.
- Keep it boiling for 3 hours.
- Remove the mould and allow it to cool to room temperature.
- Measure the final distance (A₂) between the indicator points.
🧮 Calculation
Expansion = A₂ − A₁
Example:
If A₁ = 10.0 mm and A₂ = 10.8 mm,
Expansion = 10.8 − 10.0 = 0.8 mm
📊 Observation Table
| Sample | Initial Distance (A₁) | Final Distance (A₂) | Expansion (mm) |
|---|---|---|---|
| Cement Sample 1 | 10.0 | 10.8 | 0.8 |
| Cement Sample 2 | 10.1 | 10.9 | 0.8 |
📋 Permissible Limits (as per IS: 269 and IS: 4031 Part 3)
- For Ordinary Portland Cement (OPC): Expansion ≤ 10 mm
- For Rapid Hardening Cement: Expansion ≤ 10 mm
- For Low Heat Cement: Expansion ≤ 10 mm
📖 Significance
- Ensures the cement will not undergo unsound expansion after setting.
- Prevents structural defects like cracks and disintegration.
- Evaluates the presence of free lime and magnesia.
⚖️ Comparison: Le Chatelier vs Autoclave Test
| Aspect | Le Chatelier Test | Autoclave Test |
|---|---|---|
| Pressure | Atmospheric pressure | High pressure (21 kg/cm²) |
| Detects | Free lime (CaO) | Free lime and magnesia (CaO & MgO) |
| Specimen | Cement paste in split mould | Cement prism 25×25×250 mm |
| Accuracy | Moderate | High |
| Standard | IS 4031 (Part 3) | IS 4031 (Part 3) |
⚠️ Precautions
- Ensure proper alignment of indicator arms before and after the test.
- Gradually heat the water to avoid sudden expansion.
- Maintain uniform consistency of the cement paste.
- Do not disturb the mould during storage or boiling.
✅ Result
Average expansion = 0.8 mm.
Since expansion ≤ 10 mm, the cement is sound and suitable for construction.
📘 Conclusion
The Le Chatelier Test determines the soundness of cement by measuring its expansion after boiling in water. The tested cement showed an expansion of 0.8 mm, which is within the permissible limit as per IS 4031 (Part 3):1988, confirming that the cement is free from excessive lime expansion and suitable for quality construction work.