Influence of Calcination Temperature on the Physicochemical Properties of Limestone from the Aktau Deposit

Aims: To investigate the effect of calcination temperature on the physicochemical properties of carbonate rocks from the Aktau deposit in Karakalpakstan, with a focus on the relationship between firing temperature, lime reactivity, and microstructural characteristics. Study Design: Experimental laboratory study with comparative analysis across different calcination temperatures. Place and Duration of Study: Karakalpak Scientific Research Institute of Natural Sciences, Karakalpak Branch of the Academy of Sciences of the Republic of Uzbekistan, Nukus, from March to November 2024. Methodology: Limestone samples from the Aktau deposit were calcined at 800, 900, 1000, 1100, and 1200 °C. Chemical composition was determined by standard wet chemistry methods. Thermal behavior was analyzed using thermogravimetric and differential thermal analysis. Functional groups were examined by infrared (IR) spectroscopy. Microstructural features were observed by scanning electron microscopy (SEM). The reactivity of the produced lime was evaluated according to hydration rate and temperature rise during slaking. Results: Increasing calcination temperature above 1000 °C significantly enhanced the reactivity of lime, with maximum values observed at 1100 °C. SEM images revealed that higher temperatures led to coarser but more porous microstructures, improving water penetration during hydration. IR spectroscopy confirmed progressive decomposition of carbonates and formation of free CaO. Samples calcined at 800–900 °C retained partially decomposed calcite, resulting in lower reactivity. Impurity content, texture, and grain size were found to influence the hydration kinetics. Conclusion: Calcination temperature plays a critical role in determining the physicochemical properties and reactivity of lime from the Aktau deposit. Optimal reactivity is achieved at 1100 °C due to favorable microstructural development. These findings can guide industrial processing parameters to produce lime with improved performance in construction and chemical applications.