Impact of curing time on moisture-induced damage in lime-treated soils

Abstract

Long-term performance of pavement sections depends on the structural integrity and strength of its individual layers. Clay-rich soils do not often meet the structural requirements needed to perform as an effective subgrade material. Among the different in situ techniques available to enhance the engineering properties of these clay-rich soils, lime stabilisation is the most preferred alternative. Although lime treatment improves the strength properties of clay-rich soils due to sustained pozzolanic reactions, the intrusion of external water can deter the benefits of stabilisation processes. The objective of this study was to identify the possible causes of strength and durability loss in lime stabilised subgrade soil during moisture exposure and determine the effect of curing period on the extent of moisture-induced damage incurred. Reasons for immediate strength loss observed in stabilised materials when exposed to moisture conditions were also investigated as part of the study. Thermal analysis techniques, such as differential scanning calorimetry, differential thermal analysis and thermo-gravimetric analysis were used in identifying and quantifying the calcium silicate hydrate (C–S–H) phases precipitating in lime-treated soils and also to determine the water retention properties of these cementitious materials. Results suggest the inherent affinity and water holding capacity of the precipitated C–S–H phases are partially responsible for the deterioration in strength properties observed in stabilised layers exposed to water, especially during early curing periods. As curing proceeds, the increased suction potential created by the C–S–H phases is counteracted by a higher matrix strength. This phenomenon causes a reduction in external water movement and associated strength loss in stabilised layers.