The thermal and structural stability of serpentine is critical in determining its potential applications as concrete aggregate in deep geological repositories for nuclear waste disposal. This study investigates how ball milling and the thermal environment, specifically oxidizing and inert conditions, influence structural and thermal stability of antigorite serpentine. We show that prolonged ball milling of the antigorite disrupts its silicon tetrahedral sheet, leading to increased disorder in the (001) plane and collapse of the layered structure along the c-axis. Ball milling enhances the Sr \(^{2+}\) adsorption by antigorite, where early milling promotes a physisorption-dominated regime linked to BET-accessible surface area, whereas prolonged milling shifts Sr \(^{2+}\) uptake into a chemisorption regime governed by defect-rich, high-energy sites. We also find that antigorite exhibits better thermal stability against dehydroxylation in the air atmosphere than in the inert atmosphere. One of the key findings is that the thermal expansion coefficient of antigorite along the c-axis in the oxidizing air atmosphere (1.22 \(\times \) 10 \(^{-5}\) ±4.28 \(\times \) 10 \(^{-7}\) \(^{\circ }\) C \(^{-1}\) ) is an order of magnitude lower than in an inert argon atmosphere (1.39 \(\times \) 10 \(^{-4}\) ±3.39 \(\times \) 10 \(^{-6}\) \(^{\circ }\) C \(^{-1}\) ). The observed effects of thermal environment are explained in the light of Fe \(^{2+}\) \(\rightarrow \) Fe \(^{3+}\) oxidation potential, supported by the X-ray photoelectron spectroscopy (XPS) measurements. Overall, the findings highlight the pivotal role of mechanochemical activation and thermal environment in governing the stability of antigorite, providing valuable insights into the underlying mechanisms driving its structural and chemical transformation.
