Chemical analysis of contaminated soil strengthened by the addition of lime

Strengthening of contaminated materials using inorganic cementitious agents is becoming more widely used in the UK. The method has particular advantages for bulk fill operations such as highway earthworks. Research has been done into the chemical characteristics of leachates and leached solid samples from a study into the long-term durability of a lime strengthened silt/pfa mixture amended with sewage sludge. This involved determinations of chemical composition and mineralogy, and geochemical modelling using Minteqa2. None of the heavy metals tested is present in the leachate at a concentration likely to pose a significant environmental threat, although some were present to a higher degree than expected based on the inorganic chemistry. This is ascribed to complexation of the heavy metals with dissolved organic matter.