Loss on Ignition (LOI) Testing in Hydraulic Cement & Clinker
Accelerating ASTM C114 Quality Control with Multi-Sample Thermogravimetry
Executive Summary
A technical examination of Loss on Ignition (LOI) testing for cement raw meal, limestone, and clinker. How automated macro-TGA eliminates manual porcelain crucible handling and delivers simultaneous 19-sample results.1. Why LOI is a Critical Cement QC Parameter
Loss on Ignition (LOI) indicates the extent of pre-hydration and carbonation in finished hydraulic cement caused by exposure to atmospheric moisture and CO2 during storage and transit. In raw meal calcination, LOI directly quantifies uncalcined calcium carbonate (CaCO3) decomposing into quicklime (CaO) and CO2.
2. The Traditional Manual Method vs. Automated TGA
Under ASTM C114, traditional LOI testing requires heating 1.000 g of sample in a platinum or porcelain crucible inside an electric muffle furnace at 950°C ± 50°C for at least 15 minutes, cooling in a desiccator, and weighing repeatedly until constant mass. In automated macro-TGA, 19 samples are tested simultaneously with robotic weighing at 950°C, eliminating human transfer delays and ambient moisture pickup.
3. Differentiation of Hydration vs. Carbonation
By utilizing programmable temperature ramps, advanced thermogravimetric analyzers can differentiate between mass loss due to free moisture (ambient to 105°C), structural water loss from calcium silicate hydrates (105°C to 450°C), and CO2 decomposition from carbonates (450°C to 950°C).
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