One of the most present types of concrete in buildings is ultra-high-performance concrete. In contrast, large quantities of cement are consumed to achieve the required strength. To minimize the quantity of cement utilized in manufacturing ultra-high-performance concrete, this research aims to look at the usage of a unique agricultural waste as an alternative to cement. This study focuses on using agricultural waste as a partial cement alternative to reduce the amount of cement used in the production of ultra-high-performance concrete. This study employed basil plant ash as a partial substitution for ordinary Portland cement at 5 %, 10 %, 15 %, 20 %, and 25 % by mass. basil plant ash was heat-treated at temperatures of 300 °C, 500 °C, 700 °C, 900 °C. The compressive strength, splitting tensile strength, and sorptivity coefficient of ultra-high-performance concrete were investigated using 21 different mixes. In addition, microstructure characteristics as assessed using X-ray diffraction, thermal gravimetric analysis, and scanning electron microscope. The results showed that treating basil plant ash at 700 °C contributed to achieving the best mechanical properties when it was utilized as a partial substitution for 20 % of the weight of ordinary Portland cement. The compressive strength and splitting tensile strength were enhanced by 15.07 % and 20.39 %, respectively, compared with the control mix at 28 days. The thermo-gravimetric analysis, X-ray diffraction, and scanning electron microscope analyses are consistent with the obtained mechanical and durability characteristics. The outcomes of this investigation help shed light on the use of basil plant ash as a partial substitution at a level of 20 % of the weight of cement to produce ultra-high-performance concrete with high performance and lower cost.