A review on alternatives to calcium-based stabilizers in high sulfate bearing soils
Although stabilization of sulfate bearing soils using calcium based stabilizers such as lime, cement, and class C fly ash, has been widely applied by engineers in different development projects over the years, premature destruction of these stabilized soils and the structures built on them, in some projects, due to heaving, brings into question the validity of sulfate subgrades treatment with these additives. Reaction among sulfate and alumina present in the soil and calcium in the stabilizer, can lead to formation of expansive crystalline minerals, called ettringite and thaumasite. These products are considered as the main cause of sulfate-induced heave phenomenon. Therefore lack of comprehensive knowledge of sulfate containing soils behavior can cause occurrence of undesirable consequences and irreparable damage. This paper provides a comprehensive framework of the sulfate soils characteristics and different techniques for the geotechnical properties improvement of these soils. Based on the results of different experimental studies and field experiences, this review refers to the pivotal role of sulfate concentration and plasticity index of the soil in the use of calcium based stabilizers. It also introduces alternatives to these additives in high sulfate bearing soils to remedy the above-mentioned problem, namely sulfate induced heave.