Abstract
Exposure of lime treated expansive soil to sulphatic compounds are known to develop distresses due to the formation of ettringite or thaumasite, causing excess swell and alteration in strength behaviour. However, effect of wetting–drying (W-D) cycles caused due to seasonal variations on the behavior of lime treated soil exposed to sulphate contamination has not been addressed properly. Hence, present work investigates the impact of varying W-D cycles (0–4) on unconfined compressive strength (UCS) behaviour of lime treated soil in presence of two different sulphatic [i.e., monovalent sodium sulphate (Na2SO4) and divalent gypsum (CaSO4·2H2O)] contaminations. Lime treated soil samples are, firstly, cured for 7, 14 and 28 days and then used for further process of W-D cycles after completion of each curing periods. Varying sulphate concentrations (i.e., 3000, 10000, 16000, 20,000 and 30000 ppm) as prepared by using Na2SO4 and CaSO4·2H2O using distilled water have been used as contaminating solutions in W-D cycles process for lime treated soil. Strength behaviour of samples subjected to W-D cycles are determined at both wet and dry sides of each cycle. The results revealed that strength of lime treated soil is influenced highly by sulphatic concentration, types of sulphatic compound (monovalent or, divalent cations), curing periods as well as number of W-D cycles. Adverse impacts on strength are pronounced with an increase in sulphate concentration and number of W-D cycles. However, significant adverse effect on strength and durability are pronounced in the samples subjected to sulphate concentration more than 16000 ppm. Further, study is extended to elucidate the experimental results with physicochemical behaviour and microanalyses [XRD, FESEM, EDAX, FTIR and TGA-DTA]. It is confirmed that progression of number of W-D cycles with the increase in sulphatic concentration has influenced significantly to the microstructure of lime treated soil.
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