Investigation of lime stabilised contaminated material

摘要

Stabilistaion of contaminated materials usinginorganic cementitous agents is becoming more widely used inthe UK. The method has particular advantages for bulk filloperations such as highway earthworks. Research has beencarried out at the Transport Research Laboratory into the long-term durability of lime stabilised material. The trial material wasa soft organic silty clay with metal contamination. Testing in acombined permeability and leaching apparatus with distilledwater and dilute sulphuric acid as leachants is described and theresults compared with those obtained using the National RiversAuthority (NRA) interim leaching test.All samples had retained their high shear strength by the end ofthe leaching tests. Permeabilities were consistently very low, inthe range 1×10-9m s-1, and the pH of the elate remained stable at>12. The chemistry of the eluate showed an initial peak inconcentration of mobile ions such as sodium and chloride,whereas the calcium concentration remained steady throughout.Concentrations of most of the metals in the eluate were belowdetection limits, but concentrations of copper, nickel and phenolsshowed a similar pattern to sodium and chloride, with high initialconcentrations decreasing as the test progressed. The resultssuggest that the stabilised material retains its integrity in the long-term. However, the mobility of individual contaminants appearsto depend on their speciation, and further work is required toevaluate this. Tests are also being carried out to assess thebehaviour of stabilised materials in the field, to compare with theresults of the laboratory tests described in this paper.