Optimizing calcination for low-grade calcined kaolinite clay: Reactivity and energy consumption

The cement industry is actively seeking sustainable strategies to enhance efficiency and reduce its environmental influences. Calcined kaolinite clay (CC) has emerged as a promising supplementary cementitious material (SCM) that offers significant cost and carbon emission reduction emissions compared to traditional materials. However, the variability in calcination conditions due to differing procedures and clay properties often leads to sub-optimal outcomes, diminishing pozzolanic reactivity and strengths. To address this, we developed an empirical model that accurately predicts energy consumption in relation to the metakaolin (MK) transformation ratio, enabling more efficient and sustainable production processes. Our study investigates the effects of different calcination conditions on low-grade CC by analyzing its physical and chemical characteristics, thermal decomposition, reactivity, and thermodynamics. We identified optimal calcination conditions at 800°C for 180 minutes using an electric furnace, achieving the highest pozzolanic reactivity and mechanical strength while enhancing the slump value by up to 40 %. The proposed model demonstrates a robust correlation coefficient of approximately 0.97, providing reliable energy consumption predictions across various calcination scenarios. This research provides valuable insights into balancing energy efficiency with material performance in low-grade CC calcination processes to augment sustainable development initiatives of the cement industry. • CC is found sensitive to calcination conditions via morphological changes from SEM. • 800°C/180 mins is the optimal condition for CC dehydroxylation and lowers the PSD. • CC calcined at 800°C/180 mins yields ideal workability and reactivity in cement mixes. • The empirical equation correlates MK transformation and energy consumption (R²=0.97).