Stabilisation/solidification of radionuclide polluted soils — Part I: Assessment of setting time, mechanical resistance, γ-radiation shielding and leachate γ-radiation

• We assess the effects of 232Thorium contamination on performance of S/S treated soil.
• We assess the γ radiation shielding of the materials used for S/S.
• Investigated parameters influence the performance of the S/S treated matrices.
• Barite gives high γ radiation shielding and low contaminant leaching.
• Results indicate S/S as an optimal choice to treat radionuclides polluted soil.

Stabilisation/solidification treatment was performed in order to assess the possibility of remedying radionuclide polluted soils. A sandy soil, spiked by Thorium oxide (ThO2) at levels of 2.2 and 5.0%, was stabilised/solidified (S/S) using different binder mixtures of Portland cement (32.5 Rck and 42.5 Rck) and barite aggregates at different soil-binder ratios and tested for its setting time, unconfined compressive strength (UCS), γ radiation shielding and contaminant leaching.Results obtained from setting time tests showed that different treatments do not influence the performance of the treatment, whereas the level and the type of cement used significantly influenced the mechanical resistance of the S/S materials. The presence of the barite aggregates mixed with cement also gives a significant containment of the γ radiation and an excellent reduction of contaminant leaching but it slightly reduces the performance in terms of mechanical resistance, possibly representing an optimal choice to S/S treat low level radionuclide polluted soil. The obtained preliminary results are of scientific and practical interest and may be used in further research, whereas complete results will represent a suitable tool to optimize the treatment operating conditions and to guide the design and the scale-up of S/S treatment systems in full scale remediation activities of radionuclide polluted soils.