Plastic Shrinkage Cracking of Limestone Calcined Clay Cement Concrete in Normal and Extreme Climates: Influence of Superplasticiser

Limestone calcined clay cement (LC 3 ) has emerged as a promising low‐carbon alternative to ordinary Portland cement (OPC). However, its early‐age cracking, particularly plastic shrinkage cracking, remains underexplored. This study investigates the plastic shrinkage and cracking behaviour of LC 3 concrete under normal and extreme climates and evaluates the mitigating role of superplasticiser. OPC was partially replaced with 0%, 30%, 45% and 60% limestone calcined clay (LC 2 ), namely, CEM I, LC 3 ‐30, LC 3 ‐45 and LC 3 ‐60, respectively. The plastic shrinkage cracking of the mixes was monitored using the digital image correlation (DIC) technique. In normal and extreme climates, LC 3 mixes exhibited more than twice the total crack area compared to the control (CEM I). Crack initiation occurred earlier in LC 3 mixes, and cracking severity increased with a higher LC 2 content. This is attributed to the reduced bleeding, higher evaporation rates and higher plastic shrinkage strains in the LC 3 mixes. Differences in setting behaviour between extreme and normal climates were also observed, influencing the timing of shrinkage strain stabilisation in LC 3 mixes. The incorporation of superplasticiser substantially reduced the plastic shrinkage cracking across all LC 3 mixes. Quantitatively, the crack area was reduced by up to 40% under normal climate conditions and ~25% under extreme climate conditions, relative to LC 3 mixes without superplasticiser. Overall, the results demonstrate that while LC 3 concrete is more vulnerable to plastic shrinkage cracking than OPC, appropriate superplasticiser optimisation can significantly mitigate crack severity.