Effect of Natural Pozzolan and Waste Glass Powder on the Mechanical Properties of Mortars Containing Polypropylene Fibers Utilizing Response Surface Methodology

This research shows the combined effects of natural pozzolan (NP) and waste glass powder (WGP) on the mechanical strength of polypropylene fiber (PPF)-reinforced cement mortars. As the construction sector is looking for alternatives to traditional binding materials, this study addresses the challenge of reducing carbon footprints. A dataset of 405 test results for compressive strength (fc), tensile strength (ft) and flexural strength (fr) was used to model and optimize the impact of partial replacement of cement with NP and WGP at replacement levels up to 20 and 30% by weight, respectively, and PPF at volume levels of 0.5 and 1.5% on the strengths of mortars utilizing response surface methodology (RSM). A solution combining sodium hydroxide and sodium silicate (SH + SS) is utilized at a constant ratio. The results show that all mixes gained strength with curing age, increasing WGP generally reduced the strength at all ages, and a moderate NP content (10%) gave the highest compressive and tensile strengths. The importance and applicability of established models were evaluated, and the contributions of the variables were examined using analysis of variance (ANOVA) along with other statistical tests. Numerical optimization was utilized to identify the optimal NP, WGP, and PPF values for optimizing mortar mechanical properties. The statistical models generated via RSM exhibited high coefficients of determination (R2) of 0.9835, 0.9775, and 0.921 for fc, ft, and fr, respectively, indicating the reliability of the design in predicting mortar behavior. The highest measured strengths were obtained with 0.5% PPF, while the multi-response optimization gave about 1.0% PPF when the cement replacement was also maximized. The study concludes that an optimized blend of NP and WGP can produce eco-friendly mortars that meet structural requirements for specific masonry applications.