Comparative study of LC3 mortars using waste and natural clays: a path toward green cement

With the escalating impacts of climate change, reducing CO2 emissions from the cement industry has become a critical priority. Limestone Calcined Clay Cement (LC3) offers a viable alternative, capable of lowering CO2 emissions by 40% while maintaining mechanical performance comparable to ordinary Portland cement. However, its implementation depends on availability and reactivity of suitable calcined clays. This study investigates the feasibility of utilizing waste clay sludge from sanitary ware production as an alternative calcined clay source in LC3 manufacturing. LC3 produced with waste clay was compared with LC3 prepared using clays with different kaolinite contents. Mortars were produced with two water-to-binder ratios, and workability and compressive strength were evaluated. Phase composition and microstructure were analyzed using XRD and SEM. Pearson correlation and one-way ANOVA were employed for statistical assessment. Results showed no significant differences between waste-clay and medium-kaolinite LC3 mortars, demonstrating comparable performance and supporting sustainable, circular cement production.