مهدی نعمت زاده افروزی

In this study, the applications of Forta-Ferro (FF) fiber as a synthetic fiber type and calcium aluminate cement (CAC) as aluminous cement were investigated. FF fibers with three disparate volume fractions of 0, 0.4, and 0.7%, and CAC replacing the ordinary Portland cement (OPC) by 0 and 100% were incorporated in the mix design. After the immersion of concrete specimens in 5% sulfuric acid solution at intervals of 0 and 45 days, the influence of adding FF fibers and CAC to the concrete mix on the mechanical properties, including compressive strength, initial and secant elastic moduli, strain at peak stress, ultimate strain, compressive stress-strain curve, direct tensile strength and its corresponding strain, as well as the tensile stress-strain curve were investigated. The results show that the addition of FF fibers to the concrete mixture resulted in an increase in the compressive/tensile strength by 8/11% and 38/22% for the concrete in the acidic and non-acidic environments, respectively. In addition, replacing OPC with CAC in the concrete mix significantly increased the compressive and tensile strength by approximately 70%. The acidic environment notably decreased the compressive and tensile strength up to approximately 30% and 20%, respectively, especially for CAC specimens. Stress-strain models were also proposed via empirical equations to capture the compressive and tensile behavior of the concrete containing FF fibers under the acidic medium. Finally, by applying the response surface method (RSM), an optimal solution was recommended for design parameters through maximizing the compressive and tensile strength of concrete containing FF fiber and CAC exposed to an acidic environment.