Lime optimisation in lime-slag treated soft Coode Island Silt in Melbourne

B. Stanley, G. J. Singh, A. Haque, P. G. Ranjith and A. Bouazza

This paper aims to identify optimum lime content for lime-slag treated Coode Island Silt (CIS) for sustained improvement of strength. In this study, CIS sampled from the Convention Centre construction site in Melbourne was treated with lime-slag additives in the laboratory to determine optimum lime content. Treatment was conducted with a fixed lime content of 7.5% and varying slag contents of 0-17.5%. The treated samples were cured for 28, 90, 180 and 360 days in a humid chamber. The cured specimens were tested in the laboratory for unconfined compressive strength (UCS), pH and Atterberg limits. Scanning Electron Microscopy (SEM) and X-Ray Diffraction analyses (XRD) were also conducted on specimens cured for one year to study the physico-chemical and microstructural developments responsible for long term strength behaviour. Finally, results of this study were compared with the 5 and 10% lime and varying slag treated CIS by Rex el al. (2008) to establish the optimum percentage of lime required for long-term strength gain. This study found that an optimum lime content of 7.5% was effective in stabilizing and sustaining the strength development of CIS (LL=46, PI=24) based on curing periods up to one year.