Mechano-thermal activation of kaolinitic clay for low-carbon cement manufacture

Abstract Calcined clays are the only supplementary cementitious materials available to meet mid-century global cement demand, yet at present their calcination at 800 °C requires substantial thermal fuel input. Here we show that mechanical pre-activation introduces structural disorder in kaolinite, lowering the dehydroxylation temperature and enabling complete activation at 550 °C. A mechano-thermally activated kaolinitic clay exhibited enhanced early-age and later-age reactivity and strength compared to a thermally calcined clay. Scenario-based modelling indicates average mitigation of 22 kg CO₂ t −1 clay under current energy mixes, rising to >43 kg CO₂ t −1 under low-carbon electricity. Immediate full-scale deployment could reduce cement-sector emissions by up to 28 Mt CO₂ yr −1 . Under a fully electrified scenario, reducing calcination temperature still gives mitigation of 18–21 kg CO₂ t −1 activated clay. By shifting clay activation into a lower-temperature regime compatible with electrification and waste heat, the mechano–thermal pathway provides a scalable route toward electrification and decarbonization of the cement industry.