Microstructural properties of ordinary concrete mixed with rubber and plastic waste under aggressive environmental conditions: A full‐factorial design study

The aim of this study was to incorporate the waste plastic and rubber into concrete in order to manufacture concrete that is resistant to aggressive environments, using the factorial approach to assess the effect of different factors (rubber and plastic) on the selected responses. In this research, ordinary Portland cement and fine aggregate were partially replaced with rubber and plastic as a mass substitute in the proportions of 2% and 4% and the fine aggregate 2%, 4%, and 6%, respectively. The tests used for the fresh properties were workability and density, whereas the hardened properties were assessed using compressive strength, flexural strength, and weight loss, as well as micro‐structural analysis, XRD, and scanning electron microscopy, SEM. The results show a decrease in workability, density, compressive strength, flexural strength, and weight loss when increasing the percentage of plastic and rubber used. The workability decreases from 80 to 20 mm, and the density decreases from 2.38 to 2.20 kg/m 3 ; the compressive and flexural strengths, respectively, decreased by up to 38% and 20.5% at 28 days compared to the control concrete. Moreover, the weight loss decreases by up to 25% compared to the control concrete. In addition, SEM indicated that the voids are filled with the waste rubber and plastic and thus reduce the penetration of sulfuric acid into the concrete. This helps maintain the integrity and durability of concrete in the face of aggressive environments. The test findings were subjected to analyses of variance in order to determine the significance of the influence factors and their interactions on the chosen responses. The results show that the coefficient R 2 ranges between 0.89 and 0.99, which indicates a good correlation between the predicted and experimental modes.