Consecutive thermal and wet conditioning treatments of sedimentary stabilized cementitious materials from HPSS® technology: Effects on leaching and microstructure

Soil and sediment contamination is recognised as one of the most relevant environmental problems caused by past industrial activities and unsustainable waste disposal practices, highlighting the need to develop or improve effective remediation techniques to support sustainable management strategies. In this context, the remediation of sediments dredged from the Mincio river (Italy) contaminated by mercury and heavy hydrocarbons (C_12-40) was carried out by applying and implementing the High Performance Solidification/Stabilization technology, aimed at producing safe and reusable cement-based granular materials. The technology was improved by decreasing both the temperature and time of the thermal desorption treatment (from 280 to 110 °C and from 4-16 h to 70 min, respectively) and by including a wet conditioning step to the process. Temperature and time reduction allowed to diminish the degradation of the cementitious phases of the granules (usually related to the high temperatures employed in the process), while the wet conditioning step allowed to improve their mechanical properties, as well as to further reduce the leaching of contaminants. The physical-chemical properties of the granules and contaminant leaching in water were investigated by Inductively Coupled Plasma Mass and Optical Emission Spectrometry, Ultraviolet-Visible spectroscopy, Gas Chromatography, X-Ray Powder Diffraction, and Scanning Electron Microscopy, in order to identify the optimal parameters for both thermal and wet conditioning processes. The overall results showed that the use of consecutive thermal and wet conditioning treatment on sedimentary cementitious materials from the High Performance Solidification/Stabilization technology led to the removal of volatile pollutants and to the improvement of granule quality, thus providing a final material that satisfied all the Italian regulatory requirements for reuse. Therefore, the findings obtained in this study may contribute to the development of sustainable management strategies for contaminated soils and sediments, leading to their valorisation through the transformation into reusable materials.