A review on the influence of carbonation and chloride ingress on the durability of limestone calcined clay cement

The increasing adoption of Limestone Calcined Clay Cement (LC3) as a viable alternative to ordinary Portland cement (OPC) is driven by its global availability, cost-effectiveness, and comparable mechanical strength. However, ensuring its short- and long-term durability is essential for the longevity of the built structures. In addition to the intrinsic factors, such as reaction kinetics and thermodynamic stability of the hydration products, concrete durability is also affected by environmental exposure. The deteriorating agents can penetrate the pore network, interact with the cement matrix, and alter its microstructure. Since pore characteristics influence transfer properties, it is essential to understand the impact of environmental exposure on the pore structure of LC3 to evaluate its durability. This review focuses on the durability of LC3 with emphasis on permeability, carbonation, and chloride ingress. In LC3 systems, the synergistic interaction between clinker, calcined clay and limestone promotes the formation of calcium–alumino–silicate–hydrate (C–A–S–H) and carboaluminate phases, leading to pore refinement. LC3 exhibits enhanced chloride binding capacity and reduced resistance to carbonation. However, accelerated carbonation tests (ACT) frequently overestimate carbonation susceptibility due to elevated CO 2 concentrations, short exposure durations, and preconditioning regimes that neglect time-dependent microstructural densification, while natural exposure shows substantially lower carbonation depths. These findings highlight the need for LC3-specific durability assessment protocols that account for time-dependent microstructural evolution and environmental factors, enabling its reliable use as a durable, low-carbon alternative to OPC.