<p>This study was performed to assess the impacts of rayon fibers and gamma radiation as a modification tool for fiber strength enhancement in fiber-reinforced concrete. The available data on irradiated rayon fiber is inadequate to recognize the impact of gamma radiation on fiber and its application in fiber-reinforced concrete. Three individual fiber modification techniques were used including gamma radiation, chemical grafting, and radiation-induced chemical grafting. To evaluate optimum strength, various concentrations of radiation dosage (10, 50, 150, and 300 kGy) were applied to rayon fiber. It has been observed that gamma radiation provides optimum strength to fiber at 10 kGy radiation dosage. Various advanced techniques (scanning electron microscopic image, differential scanning calorimetry test, differential thermal analysis, and thermogravimetric analysis) were performed to characterize rayon fiber. The experimental work was performed on M- 25 grade concrete. Different concentrations of irradiated fiber percentages (0.5, 1.0, and 2%) were added to develop fiber-reinforced concrete. Fresh and mechanical tests were conducted. The optimal percentage of irradiated rayon fiber addition to the concrete was 1%, which provides 15.2% and 18.5% increments in compressive and flexural strength compared to traditional concrete. The inclusion of irradiated rayon fibers as reinforcement material had a positive impact, adding value to textile industry waste.</p>