Effect of sulphate on the shear strength of lime-treated kaolinitic soil

Abstract

Lime has been extensively used to improve the strength of fine-grained soils. It has recently been reported that the presence of sulphate in soils causes abnormal volume changes in lime stabilised soil. This paper presents the strength behaviour of lime-treated kaolinitic natural red earth in the presence of varying sulphate contents, up to 3%, after curing for periods of up to 365 days. Alteration of soil-lime reactions in the presence of sulphate leads to the formation of ettringite after curing for longer periods. The formation of these compounds affects strength development by cementation. However, after curing for short periods, the strength of lime-treated soil is improved in the presence of sulphate. It is only after curing for longer periods that the strength is decreased. Consequently the stress-strain behaviour and effective stress paths of treated soil cured for long periods show the behaviour of a normally consolidated soil rather than of cemented soils. The reduction in strength is due primarily to a reduction in the effective cohesion intercept. The effective friction angle has not been affected significantly.