Eco-friendly preparation of asbestos tailings based cementitious material: Grinding dynamics and structure formation mechanism

The storage of asbestos tailings (ATs) presents significant health and environmental risks and has been officially classified as hazardous waste in China. This issue also affects major asbestos-producing countries, including the United States, Canada, and Australia. This study seeks to address these challenges through a novel treatment approach. The proposed method involves the mechanical activation of ATs via ball grinding, analysis of the relationship between particle structure and activation parameters through grinding kinetics and microstructural characterisation, and determination of the optimal activation conditions. In this work, asbestos tailings-based cementitious materials (ATs-C) were successfully produced through the synergistic incorporation of powdered ATs, silica fume, and lightly calcined magnesium oxide. Results indicated that grinded ATs conformed to Divas–Aliavden’s grinding kinetics theory, while their particle size distribution adhered to the Rosin–Rammler–Bennett (RRB) kinetics model. After 40 min of grinding, the specific surface area of ATs reached 37.97 m²/g, and the pore structure was markedly enhanced, leading to the formation of highly reactive “secondary particles”. The maximum compressive strength of ATs-C reached 23.4 MPa, and the flexural strength was 3.88 MPa, meeting the requirements specified in ASTM C62–17 (Specification for Building Brick, Solid Masonry Units Made from Clay or Shale). Mechanical collision disrupted and reorganised the Si–O and Mg–O bonds within ATs, resulting in the formation of amorphous or low-crystallinity hydrated magnesium silicate gel. This method enables efficient, low-cost, and harmless treatment of ATs at ambient temperature, eliminates granular dust emissions, and poses no risks to human health or the natural environment. It offers an economically viable resource-utilisation pathway for the millions of tonnes of ATs stockpiled in China. • Innovative mechanical ball milling activation process for asbestos tailings. • Revealing the structural evolution mechanism of activated secondary particles in asbestos tailings. • Low-carbon asbestos tailings based cementitious material are prepared for the first time. • Opening up new possibilities for the application in the fields of ecology and construction.