Calcium-based stabiliser treatment of sulfate-bearing soils

Stabilisation of sulfate-bearing soils has proven to be a challenging engineering problem for the pavement and geotechnical engineering community. Pavement distress caused by the heaving of sulfate soils often necessitates pavement rehabilitation and frequent road closures. Although the current literature provides a few reasons for sulfate heaving, there are still remaining issues with respect to normalisation of sulfate levels at which this heave will occur in the field. This paper presents sulfate heave issues, soluble sulfate measurement techniques for soils and various factors that complicate the establishment of threshold sulfate levels. Sulfate heave mechanisms by crystal growth and ettringite hydration are explained. Then an overview is provided of various soluble sulfate measurement techniques; a couple of case histories of sulfate-induced failures are also included. A comprehensive summary is given of various alternative treatments used in an attempt to stabilise sulfate soils. In conclusion, a few other issues related to this heaving and ongoing research developments to address these issues are briefly mentioned.