Using a TGA Machine to Measure LOI in Cement
Loss on Ignition (LOI) is a critical parameter in assessing the quality and composition of cement. It measures the percentage of volatile substances – including moisture, carbon dioxide, and organic compounds – released when the cement is heated to a high temperature. This blog will detail the step-by-step procedure to measure LOI using a thermogravimetric analyzer (TGA), ensuring accurate and reliable results in compliance with ASTM C150 standards.
Obtaining a LOI Measurement From a Thermogravimetric Analyzer
1. Weighing the Empty Crucible
The first step in ascertaining an LOI measurement with a thermogravimetric analyzer is to weigh an empty crucible and record its mass. This initial mass is essential for accurately determining the mass of a cement sample and its subsequent calculations. Precision is crucial, so ensure the balance used is calibrated correctly.
2. Adding the Cement Sample
Next, add approximately 1-10 grams of the cement sample to the crucible. Then weigh the crucible with the cement sample and record the combined mass. The difference between this mass and the empty crucible mass gives the initial mass of the cement sample.
3. Heating the Sample
Place the crucible containing the cement sample into a muffle furnace. Set the temperature between 900°C and 1000°C (1650°F – 1830°F). This temperature range is sufficient to volatilize the organic and inorganic components in the cement.
4. Maintaining the Temperature
Prolong the set temperature for a duration of 15 minutes. This period ensures complete volatilization of the LOI components. Consistent temperature control during this phase is critical for the accuracy of the test.
5. Cooling the Sample
After the heating phase, carefully remove the crucible from the furnace using appropriate heat-resistant tools. Allow the crucible and the sample to cool down to room temperature in a desiccator to prevent moisture uptake from the environment.
6. Weighing the Cooled Sample
Once cooled, weigh the crucible with the cement sample again. The difference in mass before and after heating represents the volatile components that were driven off during the heating process.
7. Calculating the LOI
Calculate the LOI using the following formula:
LOI (%) = (Initial Sample mass – Final sample mass / Initial sample mass) x 100
This calculation provides the percentage of the original sample mass lost during heating, representing the LOI.
8. Ensuring Accuracy
For accuracy, it is recommended to perform the LOI test on multiple samples and calculate the average value. This approach mitigates the effect of any anomalies or inconsistencies in individual measurements.
Importance of LOI in Cement Quality
The LOI test measures the amount of volatile components in cement, including moisture, carbon dioxide, and organic compounds. According to ASTM C150 standards, the maximum allowable LOI for general-use Portland cement is 3%. A lower LOI value generally indicates better cement quality and proper storage conditions.
Safety Considerations
Conducting the LOI test involves handling high temperatures and potentially hazardous materials. It is crucial to use proper safety equipment such as heat-resistant gloves and face masks. Always operate the muffle furnace in a well-ventilated area. Doing this will prevent the inhalation of any fumes released during the heating process.
Examine LOI with a TGA Machine from XRF Scientific
By utilizing the previous steps, one can reliably assess LOI through a thermogravimetric analyzer and thus the overall quality of the cement. Adhering to safety protocols and performing the test on multiple samples further enhances the reliability of the results.
For more information on using thermogravimetric analyzers, we invite you to read our beginner’s guide to thermogravimetric analysis. Our article about thermogravimetric analyzers and their processes offers in-depth explanations and additional tips to help you master the use of a thermogravimetric analyzer and achieve precise, reliable results.
At XRF Scientific, we not only provide educational resources but also supply cutting-edge thermogravimetric analyzers, such as our xrTGA 1100. This advanced thermogravimetric analyzer is perfect for measuring LOI in cement, offering extremely high throughput with its 30-sample carousel, user-friendly interface, and rapid heating and cooling cycles. Implementing our thermogravimetric analyzers can significantly enhance the accuracy and efficiency of your testing processes.
Explore our range of thermogravimetric analyzers and see the difference they can make in your work.
