ANOVA–RSM Analysis for Predicting and Optimizing the Mechanical Response of Concrete Incorporating Waste Brick Aggregates After Elevated Temperatures

Throughout their service life, concrete buildings are subjected to a number of significant degradation processes, one of which is exposure to high temperatures. This degradation degrades the mechanical and physical properties of concrete, resulting in a reduction in its strength. Consequently, it is essential to enhance the qualities of concrete at elevated temperatures. Therefore, this study examines the synergistic effects of WBA content and temperature on the mechanical properties of concrete, emphasizing sustainability and high-temperature durability. WBA substituted fine aggregate at 0–50% by mass, and specimens were subjected to ambient and elevated temperatures up to 800 °C prior to testing for compressive strength (CS), flexural strength (FS), and splitting tensile strength (STS). Two-way ANOVA established that both WBA and temperature had statistically significant effects (p < 0.05) on all strength measures, with WBA accounting for the bulk of the variation. At 24 °C, augmenting WBA from 0% to 50% enhanced CS, FS, and STS by 37.26%, 40.63%, and 32.86%, respectively. Elevated temperatures diminished all strengths, with STS exhibiting the most significant relative decline, especially beyond 400 °C. response surface methodology (RSM) models exhibited exceptional prediction accuracy (R2 > 0.97) and indicated that WBA mitigates strength loss due to elevated temperatures.