From HPC to HPSS: The use of superplasticizers for the improvement of S/S technology

This paper presents an S/S treatment which is based on the principles of High Performance Concrete (HPC). By using superplasticizers and hydrophobic additives, the proposed process allows the transformation of contaminated soils and sediments into low water to cement ratio (W/C) granular materials. These grains are characterized by lower porosity, lower leaching rate of inorganic contaminants and lower water absorption as well as higher mechanical properties and improved durability compared to solidified products obtained without additives. Moreover, the mixing water may be reduced more than 25%. The results of X-ray microtomography and mercury intrusion porosimetry measurements carried out on samples prepared with and without additives are illustrated here. Volatile and/or semi-volatile organic pollutants, if present, can be removed from the granular material by a steam distillation step, at relatively low temperature (max 250°C) and under vacuum (P < 0.1 bar) in excellent yield. The resulting aggregates are suitable for the re-utilization as backfilling, concrete aggregates or may be employed for covering landfills and in other civil engineering projects.