Geotechnical properties of biosolids stabilised with lime and cement

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Published 25 February 2015
Geotechnical properties of biosolids stabilised with lime and cement

Biosolids are a mixture of water and organic material, which are a by-product from domestic and industrial sewage treatment processes. Biosolids for this research were obtained from a wastewater treatment plant located in west of Melbourne, Australia. As part of this research, an extensive suite of geotechnical tests were undertaken on wastewater biosolids stabilised with the optimum percentage of lime and cement, to evaluate their properties and potential use as an embankment structural fill material. Engineering tests undertaken include moisture content, specific gravity, Atterberg limits, particle size analysis, organic content, standard compaction, California Bearing Ratio, hydraulic conductivity, pH, consolidation and unconfined compression strength. This paper describes the procedures followed to determine the optimum dosage of lime and cement as stabilisers for biosolids samples. Test results on pure biosolids indicate high initial moisture content, Low pH value and average organic content compare to other organic soils. The standard compaction results indicate that the stabilisation of biosolids with both additives increase the maximum dry density and decrease the optimum water content. Reduction in liquid limit and plasticity index was noticed when additives were added to biosolids. Results indicate that the hydraulic conductivity values of biosolids decrease with optimum percentage of additives, which is an indication of decreasing void ratio of material. The compressibility of biosolids was improved by additives specially lime treated samples. Both stabilisers significantly raise the CBR value and unconfined compressive strength of pure biosolids. Possible applications of the stabilised mixture in road embankments are also discussed.

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