Effect of calcination temperature on Portland cement clinker partially replaced with calcined limestone overburden clay

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Abstract Calcined limestone overburden clay was investigated as a supplementary cementitious material (SCM) for partial clinker replacement. Cement blends containing 30%, 50%, and 70% calcined clay, produced at 500–800°C, were cured for 1–90 days and evaluated for mechanical, durability, chemical, and microstructural properties. Calcination at 600°C produced optimum performance, with the 30% replacement mixture achieving 40.0 MPa compressive and 5.9 MPa flexural strengths at 90 days, compared with 54.0 and 7.8 MPa, respectively, for the CEM I control. The combined SiO 2 , Al 2 O 3 , and Fe 2 O 3 content exceeded 70 wt %, confirming substantial pozzolanic potential, while water absorption remained below 10%. Multiple linear regression and ANOVA indicated that calcined clay replacement significantly influenced compressive and flexural strengths ( p < 0.05), whereas calcination temperature was statistically insignificant ( p > 0.05). The models demonstrated strong predictive performance, with R 2 values of 97.96% and 95.00% for compressive and flexural strengths, respectively. XRD and SEM–EDS confirmed quartz and silica‐rich phases in the calcined clay. Overall, limestone overburden clay demonstrates potential as an effective SCM for reducing clinker consumption, CO 2 emissions, and environmental impacts of cement production.

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