Geotechnical characteristics of aged biosolids stabilised with cement and lime

Biosolids are the remains of the sewage treatment process, which are a mixture of both organic and inorganic compounds including household and industrial wastes. Recent attempts have been made to stabilize biosolids with special admixtures, in order to improve their geotechnical properties. The aim of this paper is to report the results of a geotechnical laboratory investigation on waste-water biosolids stabilized with different percentages of cement and lime. Biosolids were sourced from the Western Treatment Plant (WTP) in Melbourne, Australia. Compaction, California Bearing Ratio (CBR), swell, hydraulic conductivity, consolidation, creep and triaxial tests were carried out on the compacted specimens. Both static and standard proctor compaction methods were used to prepare the test specimens in this research. The results suggest that the permeability values of biosolids decrease consistently by increasing the amount of lime and cement. In addition, increasing the amount of additives decreased the compression potential of biosolids. The strength of the biosolids samples increased with the addition of lime and cement but the highest shear strength was achieved with 3% cement. This paper concludes with a discussion of possible applications of the stabilized mixture in road embankments.