Chemical-Physical Characterization of Stava Tailings Subjected to an Innovative Aging Technique

Tailing dams are realized to store the waste products resulting from the mining extraction processes. These complex geotechnical structures should be designed taking into account long-term stability and long-term properties of the deposited materials. Depending on the interactions between source mineralogy and local conditions, tailing wastes can undergo aging processes with chemical and physical modifications. Recently, in many countries tailing wastes are re-used as feedstock for cement and concrete, backfill or landscaping material, so if any, the long-term chemical and physical modifications could affect the hydro-mechanic response of tailings, resulting in relevant environmental and economic consequences. An increased interlocking of particles and oxidation, sometimes making previously safely held contaminants available and mobile, are recognized as common aging processes. Among the long-term aging processes, the natural ionizing radiation due to ultraviolet rays or cosmic rays can be considered. Moving from these reasons, this paper presents an innovative accelerated aging technique to simulate the natural ionizing radiation from the sun. Tailing fluorite ore samples collected form the collapsed Stava dams (Italy) were characterized in dry and wet conditions, before and after the gamma rays treatment. Stava silty tailings showed some physical modifications in terms of specific surface, size particle distribution and inner porosity of the particles, while they revealed a certain chemical stability.