🔥 Loss on Ignition (LOI) Test of Cement
🔍 Purpose
The Loss on Ignition (LOI) test determines the amount of volatile substances (mainly moisture, CO₂, and organic matter) lost when cement is heated to a high temperature. It is a measure of cement’s stability, freshness, and proper storage condition. The test helps identify deterioration due to prolonged exposure to air and moisture.
📘 Reference Standard
- IS 4032:1985 – Methods of Chemical Analysis of Hydraulic Cement
- IS 269:2015 – Specification for Ordinary Portland Cement
🧪 Apparatus Required
- Porcelain or platinum crucible
- Analytical balance (accuracy ±0.001 g)
- Muffle furnace capable of maintaining 900 ± 50°C
- Desiccator
- Tongs and gloves
⚙️ Procedure
- Weigh about 1 g of cement sample and record it as W₁.
- Place the sample in a clean, dry crucible.
- Heat the crucible in a muffle furnace at 900 ± 50°C for 15 minutes.
- Remove and cool it in a desiccator for 30 minutes to prevent moisture absorption.
- Weigh the cooled sample again and record as W₂.
📐 Formula
Loss on Ignition (LOI) % = ((W₁ − W₂) / W₁) × 100
Example:
If the initial weight (W₁) = 1.000 g and the final weight (W₂) = 0.952 g, then:
LOI = ((1.000 − 0.952) / 1.000) × 100 = 4.8%
📊 Permissible Limits (as per IS 269:2015)
| Type of Cement | Maximum LOI (%) |
|---|
| Ordinary Portland Cement (OPC) | 5.0% |
| Portland Pozzolana Cement (PPC) | 5.0% |
| Portland Slag Cement (PSC) | 4.0–5.0% |
📈 Interpretation of Results
- LOI ≤ 5% → Cement is fresh and stable.
- LOI > 5% → Indicates deterioration or carbonation due to improper storage.
🧭 Significance of LOI Test
- Ensures cement has not absorbed moisture or CO₂ during storage.
- Helps identify expired or damaged cement batches.
- Indicates presence of unburnt fuel or organic matter in manufacturing.
⚠️ Causes of High LOI
- Prolonged exposure to atmosphere (moisture absorption).
- Incomplete burning of raw materials during clinker formation.
- Presence of uncombined calcium hydroxide (Ca(OH)₂) or carbonates (CaCO₃).
- Contamination during packaging or storage.
✅ Precautions
- Use a clean, dry crucible.
- Maintain proper furnace temperature (900 ± 50°C).
- Cool in a desiccator immediately after heating.
- Handle the sample with tongs to avoid contamination.
📘 Conclusion
The Loss on Ignition test is an important chemical test to assess the quality and soundness of cement. A high LOI value indicates old or deteriorated cement, while a low value confirms freshness and proper manufacturing. For Ordinary Portland Cement, the LOI should not exceed 5% as per IS 269:2015.