Experimental Study on High-Strength Concrete with Hybrid Limestone Calcined Clay Cement Blends

The high demand for sustainable alternatives to ordinary Portland cement (OPC), due to its high share of global CO₂ emissions, has led to research to new low-carbon binders. One such binder is limestone calcined clay (LC3) which provides environmental benefits while preserving similar structural and durability qualities. This study explores the viability of using calcined clay and limestone to partially replace OPC in high-strength LC3 concrete, while using polycarboxylate-based superplasticizers. Two types (Fluidum PC314 and PCE CT50) of superplasticizers were employed at (0.5%, 1%, and 2%) dosages by mass of the binders. Several experiments were carried out including calorimetry test to evaluate hydration behavior at various temperature (23, 30, and 40 °C) to observe the changes in hydration behavior, measurement of fresh properties by slump, evaluation of hardened properties such as compressive strength, tensile strength, density, water absorption, chloride migration, drying shrinkage and SEM for microstructural analysis. According to the results, the LC3 concrete mixes attained a high compressive strength of around 70 MPa and 90 MPa at 7 and 28 days, respectively, which were comparable or even higher than those of the control OPC mixtures. Fluidum PC314 containing mixtures performed better mechanically and in terms of endurance than PCE CT50. In LC3 combinations, improved microstructural densification and decreased chloride permeability were noted, indicating their potential for long-lasting, high-strength uses in environmentally friendly building, which validates the research hypothesis recommending LC3 binder for use in the construction industry requiring high-strength concrete.