Comprehensive evaluation of carbonation and leaching reactions in lime-stabilised soils

The long-term performance of lime-stabilised earthworks is a major concern for the sustainability and durability of infrastructure. This paper presents a comprehensive investigation into the impact of carbonation and leaching on lime-stabilised soil by focusing on mechanical, chemical and microstructural changes. This study employed accelerated carbonation experiments with carbon dioxide levels at 3% for 7 days on lime-treated soil cured for up to 365 days. For leaching experiments, the treated samples were subjected to water percolation under a hydraulic head of 15 kPa for 14 pore volumes of flow. The results showed that carbonation reduced the compressive strength and stiffness of lime-treated soil, impacting its load-bearing capacity. The micro-level analyses revealed carbonation of cementitious gels and excess carbonate precipitation to cause a reduction in particle-to-particle bonding and loss of mechanical strength. The ingress of moisture into lime-stabilised soil led to leaching and the dissolution of cementitious gels. The effects of water percolation were insignificant for specimens cured for extended periods due to their reduced hydraulic conductivity, which resulted in enhanced cementation over leaching. Further, presaturation or treatment with a higher lime content reduced the extent of leaching. The study reveals that exposure of short-term-cured soil or soil treated with an inadequate lime content to carbon dioxide or moisture can affect their engineering properties, contrary to the design expectations.