Geotechnical properties of lime-treated gypseous soils

Abstract This paper presents the results of an experimental research study on the behavior of gypseous soils treated with lime. The aim of this work was to investigate the effect of a wide range of gypsum content and curing conditions on two important geotechnical properties: the mechanical strength and swell potential of lime-treated fine-grained soil. For this purpose, soil samples were prepared with different gypsum content (0%, 5%, 15% and 25%), treated with lime and assessed at different curing times and temperatures. The results for untreated gypseous soil showed that the unconfined compressive strength increases and the swell potential enhances with the presence of gypsum. The geotechnical properties of the lime-treated gypseous soil depend not only on the gypsum content but also on the curing conditions. An approximate doubling of the unconfined compressive strength of soil samples cured for 28 days was observed when the curing temperature was increased from 20°C to 40°C. Moreover, the swell potential increased with curing times and decreased with curing temperature in the lime-treated gypseous soil. The tests carried out at the microscopic level showed the formation of calcium silicate hydrates (CSH) and calcium aluminate hydrates (CAH), which are responsible for strength development in the treated soil samples. Further, the ettringite mineral, which induces swelling, was also observed in the treated soils.