A hydraulic binder for 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.