Laboratory Investigation of the Effect of Fly Ash and Shape Memory Alloy on the Mechanical Behavior of Concrete

Urbanization and construction have increased the demand for concrete, a key material in civil engineering that significantly contributes to environmental pollution. Improving concrete quality while reducing its environmental impact is essential. Using fibers and pozzolans in concrete can enhance its properties and address environmental issues. According to previous studies, the lack of research on the combination effect of fly ash as a pozzolan from industrial waste and shape memory alloy (SMA) as a type of fiber on the mechanical properties and dynamic modulus of elasticity (DMOE) of concrete became the basis of this laboratory study. Therefore, fly ash pozzolan and SMA fiber were used in the concrete structure in this study, and over a 28‐day period, the compressive strength, splitting tensile strength, flexural strength, secondary compressive strength, and ultrasonic pulse velocity (UPV) tests were conducted. Results showed that replacing up to 20% of cement with fly ash enhanced compressive strength by 7%, splitting tensile strength by 4%, and flexural strength by 2%. Similarly, SMA fiber increased compressive strength by 2%, splitting tensile strength by 5.5%, and flexural strength by 8% compared to the control sample. In the combined design using 20% fly ash and 0.3% SMA fiber, the best results were achieved, with increases of 7% in compressive strength, 6.5% in splitting tensile strength, and 11% in flexural strength. Due to the superelasticity of the SMA fiber, the secondary compressive strength only decreased by 16%, whereas in other samples without this fiber, the decrease was close to 30%. UPV test results revealed that the simultaneous use of these two materials provides good and acceptable quality concrete. Moreover, the correlation analysis results indicated that the compressive strength of samples containing SMA fiber showed a high correlation with their secondary compressive strength results, while the compressive strength of fly ash samples had a high correlation with the flexural strength results of fly ash‐modified samples. Finally, it can be concluded that the simultaneous use of fly ash and SMA can achieve stronger concrete, in addition to using less cement and protecting the environment. Also, the application of SMA can be economically justified in critical infrastructure where improved crack resistance, durability, and extended service life reduce long‐term maintenance and repair costs.