Compaction of fills involving stabilisation of expansive soils

Stabilisation of sulphate-bearing soils with lime/cement-based binders has always been problematic, owing to excessive sulphate-induced expansion. This paper reports on investigations conducted on the consistency and compaction properties of Lower Oxford Clay (LOC), a sulphate-bearing soil that has been difficult to stabilise in the traditional manner using lime. In the investigations, LOC was stabilised both in the conventional manner using lime as the control, and also using a wide range of sustainable stabilisers incorporating industrial waste and by-product materials. The sustainable binders included wastepaper sludge ash (WSA) used on its own, as well as binary binders comprising WSA–lime, WSA–Portland cement (PC) and WSA–ground granulated blastfurnace slag. The results obtained showed that the blended stabilisers incorporating WSA were able to modify the soil by reducing the plasticity index, coupled with good compaction, strength and volume stability properties. The findings suggested that there are economic and environmental advantages of utilising WSA and similar industrial by-products in the modification and compaction of soils, including sulphate-bearing clay soils, as equal or at times superior alternatives to the traditional stabilisers of lime and/or PC.