RSM OPTIMIZATION OF MECHANICAL AND DURABILITY PROPERTIES OF SELF-COMPACTING CONCRETE INCORPORATING ZINC ASH AND BLASTING GRIT NANOPARTICLES

Abstract

In concrete mixtures, Portland cement is a common building material. Replacing part of the cement with supplementary cementitious materials (SCMs) can make concrete more environmentally friendly, improve its properties, and reduce its cost. This study investigates the mechanical performance of self-compacting concrete (SCC) incorporating two SCMs, zinc ash (ZA) and blasting grit (BG), which are which are industrial waste by-products used as partial cement replacements. The average particle size for BG and ZA are 300 nm and 60 nm, respectively, and both materials have high specific gravity and a spherical particle shape. The experimental program was designed using Response Surface Methodology (RSM), and the mix proportions were optimized to achieve the best performance. Using a Box-Behnken design under RSM, experiments were conducted to model and optimize the compressive strength (CS) and flexural strength (FS) of SCC, leading to the development of mathematical models. The independent variables were the mass percentages of ZA (0–0.75%), BG (0–1.5%), and curing time (7, 14, 21, and 28 days). Analysis of Variance (ANOVA) confirmed the statistical significance of the models, with R² values exceeding 95% for both strength properties. The optimal mix was found to contain 0.5% ZA and 1% BG, which resulted in a 21.2% increase in 28-day compressive strength and a 17.8% improvement in flexural strength compared to the control mix. The combined use of ZA and BG not only enhances mechanical properties but also promotes waste valorization in concrete production. The RSM approach provided a reliable predictive model for identifying strength-efficient mix proportions, offering a practical tool for sustainable SCC mix design.