Enhancing concrete mechanical properties using nano-silica, calcined clay, and glass fibers optimized by response surface methodology

This study investigates the combined effects of nano-silica, calcined clay, and glass fibers on the mechanical properties of normal-grade concrete (M30), with a primary aim to utilize industrial waste materials and improve concrete performance while promoting environmental sustainability. Response Surface Methodology (RSM) was employed to optimize material proportions and evaluate their impact. The experimental design incorporated nano-silica (0– 10%), calcined clay (0–30%), and glass fibers (0–2%), corresponded to the minimum and maximum values in the range. A total of 120 specimens were tested to assess compressive strength, flexural strength, rebound hammer values, and ultrasonic pulse velocity (UPV). The optimized mix predicted compressive strength of 49.41 MPa, flexural strength of 9.05 MPa, rebound hammer value of 62 MPa, and UPV of 5445 m/s. Validation tests demonstrated observed compressive strength of 46.55 MPa, flexural strength of 8.05 MPa, rebound hammer value of 60 MPa, and UPV of 4890 m/s, with errors of 5.79%, 11.00%, 3.22%, and 10.19%, respectively. Analysis of variance (ANOVA), a statistical method for determining the significance of factors on observed outcomes, indicated that nano-silica had the most substantial impact on all performance metrics. The models showed high reliability, with R² values of 0.9653 for compressive strength, 0.9268 for flexural strength, 0.9266 for rebound hammer, and 0.8894 for UPV. The study demonstrates the potential of incorporating waste materials like calcined clay and nano-silica into concrete to enhance its mechanical properties and reduce environmental impact. This approach aligns with sustainable construction practices by lowering reliance on traditional cement, reducing carbon emissions, and promoting the reuse of industrial by products. The findings support the development of cost-effective, durable, and eco-friendly infrastructure, addressing the dual objectives of improved performance and environmental sustainability.