EXPERIMENTAL INVESTIGATION ON THE MECHANICAL PERFORMANCE OF ECO-EFFICIENT CONCRETE WITH PARTIAL REPLACEMENT OF CEMENT BY CALCINED CLAY

Abstract

The increasing demand for sustainable construction materials has necessitated the exploration of alternative supplementary cementitious materials to reduce the environmental impact associated with conventional cement production. In this context, calcined clay has emerged as a promising eco-efficient substitute due to its pozzolanic reactivity and widespread availability. The present study investigates the mechanical performance, microstructural characteristics, and multi-criteria optimization of calcined clay–based concrete with varying replacement levels and process parameters. An experimental program was designed by varying calcined clay replacement levels, water–cement ratios, and curing durations. Mechanical properties, including compressive, split tensile, and flexural strengths, were evaluated at different curing periods. Microstructural assessment was carried out using scanning electron microscopy to examine morphological features and matrix densification. Furthermore, sensitivity analysis was performed to quantify the influence of governing parameters, and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was employed to identify the optimal mix configuration based on multiple performance criteria. The results indicated that an optimal calcined clay replacement level of 10% yielded the highest performance, with compressive strength reaching 40.5 MPa, split tensile strength of 3.7 MPa, and flexural strength of 5.3 MPa. Microstructural observations confirmed enhanced matrix compactness, reduced porosity, and improved interfacial bonding due to secondary calcium silicate hydrate formation. Sensitivity analysis revealed that curing duration and replacement percentage significantly influenced strength development, whereas curing temperature exhibited comparatively lower impact. The TOPSIS analysis identified the most efficient mix with the highest closeness coefficient, indicating superior multi-performance characteristics.