Stabilisation of clayey soils with industrial by-products: part B

The use of industrial by-products in the stabilisation of problematic soils presents economic, environmental and social benefits. The geotechnical and physico-chemical behaviour of some Australian clayey soils of contrasting mineralogy stabilised with commonly employed industrial by-products has been investigated in the laboratory for developments in pH, plasticity, and undrained shear strength at curing periods of up to 1 year. Stabilising agents including hydrated lime, fly ash and ground granulated blastfurnace slag (‘slag') were utilised. The results of this study showed that soils mixed to moisture contents well above their respective liquid limits developed substantial undrained shear strength directly upon exposure to cementitious stabilisers and continued to gain significant strength thereafter. It is noteworthy that samples treated with slag activated with hydrated lime gained more strength at shorter periods of curing than comparable samples of activated fly ash and samples simply treated with equivalent proportions of hydrated lime. The pH measurements gave an indication of cementitious activity that was closely aligned to the development of undrained shear strength, where a reducing pH was observed to consistently coincide with gains in strength. Plasticity tests indicated that smectite-dominant soils have a reduction in plasticity index, while kaolinite-dominant soils have an increase in plasticity index as strong inter-particle bonds are formed. This study also found that organic matter obstructed cementitious activity. The underlying micromechanical aspects related to geotechnical response have been detailed in an accompanying paper by the authors (part A).