Weathering of a lime-treated clayey soil by drying and wetting cycles
Résumé
Lime treatment induces several time-dependent physico-chemical processes (cation exchange, pozzolanic reactions, etc.) that result in the bonding of soil particles. This treatment can reduce the swelling properties of clays and improve their strength. Nevertheless, these positive effects of lime-treatment could be altered by weathering in the very long term. In this paper, the effects of successive drying/wetting cycles on the hydro-mechanical properties of a lime-treated clayey soil are considered. Quicklime-treated samples were subjected to successive controlled-suction (osmotic technique) drying/wetting cycles; and also severe hydric cycles corresponding to an alternation of oven drying and saturation. The effect of quicklime dosage and curing time were considered. The results show a progressive increase of the swelling properties of the material and a progressive loss of strength with increasing number of drying/wetting cycles. The extent of the degradation is directly related to the amount of added quicklime and the amplitude of the suction cycles. Mercury intrusion porosimetry tests show that successive cycles lead to a progressive change of the micro-fabric, thus explaining partly the degradation of macroscopic properties. This study shows that weathering by successive drying/wetting cycles is likely to significantly alter the properties of a lime-treated soil, thus weathering effects should be accounted for the long term design of treated soil structure.