Effects of micro-silica and ceramic tile waste on the mechanical and durability properties of M40 grade concrete

The demand for sustainable materials that reduce environmental impact has increased due to the rapid growth of the construction industry. In this study, micro-silica (MS) and ceramic tile waste (CT) were used to partially replace cement and coarse aggregates, both individually and in combination, to identify the most suitable mix without compromising structural integrity. A total of eighteen mixes were prepared with varying proportions of MS (0%–12.5%) and CT (0%–50%) and were evaluated for compressive, split tensile, and flexural strength at 7, 28, and 90 days, along with water absorption and microstructural (SEM) analyses. To establish predictive relationships among mechanical properties and to identify the optimal blend, statistical optimization using the Taguchi L9 orthogonal array and regression modeling was performed. The experimental results revealed that among all mixes, the MS7.5CT30 mix exhibited superior performance, with a 1.73% increase in compressive strength, a 3.26% increase in split tensile strength, and a 3.21% increase in flexural strength at 28 days. Water absorption was reduced to 3%, confirming improved matrix density and lower permeability. Regression models demonstrated strong predictability (R2 = 0.894 for tensile strength and R2 = 0.970 for flexural strength), while ANOVA results identified ceramic tile waste (≈51%–63%) as the dominant strength-influencing factor, followed by micro-silica (25%–37%). SEM micrographs confirmed a dense, homogeneous microstructure with minimal porosity. Multi-criteria evaluation through the TOPSIS method ranked MS7.5CT30 as the optimal and most sustainable mix. Overall, this provides a framework for integrating industrial and demolition wastes into concrete production, thereby supporting low-carbon infrastructure.