A hydraulic binder for reconstituted compacted clay under wet-dry cycles: Low carbon limestone calcined clay cement

High-plastic clays with significant volume change due to moisture variations present critical challenges to civil engineering structures. Limestone calcined clay cement (LC3), an innovative and sustainable hydraulic binder, demonstrates significant potential for improving the engineering characteristics of such soils. Nevertheless, the impact of LC3 on the physico-mechanical characteristics of treated soil under a cyclic wet-dry environment remains unclear. This study for the first time investigates LC3's impact on the long-term durability of treated high-plastic clays through comprehensive macro-micro testing including physical, mechanical, mineralogical, and microstructural investigations with an emphasis on wet-dry cycles. The results revealed that LC3 treatment exhibits significant resistance to wet-dry cycles by completely mitigating the swelling potential, and a considerable reduction in plasticity resulting in enhanced workability. The compressibility and shear strength parameters have been significantly improved to several orders of magnitude. However, after six wet-dry cycles, a slight to modest reduction is observed, but overall durability remains superior to untreated soil. Cohesive and structural bonding ratios quantitatively assessed the impact of wet-dry cycles emphasizing the advantage of LC3 treatment. According to mineralogical and microstructural evaluation, the mechanism behind the adverse effects of wet-dry cycles on the compressibility and strength behavior of LC3-treated soil is mainly attributed to: (1) weakening of CSH/C(A)SH and ettringite (AFt) phases by exhibiting lower peak intensities; and (2) larger pore spaces due to repeated wet-dry cycles. These findings highlight LC3's performance in enhancing the long-term behavior and resilience of treated soils in real-world scenarios, providing durable solutions for infrastructure challenges.