High-performance concrete (HPC) stands out as a promising construction material, extensively utilized in high-rise buildings and transportation infrastructure due to its superior mechanical properties and durability. The predominant raw materials in HPC production, notably Portland cement, quartz powder, and silica fume, contribute to elevated construction costs and environmental concerns associated with extensive Portland cement usage. Addressing these challenges, limestone powder (LP) emerges as a supplementary cementitious material, enhancing concrete properties while reducing costs. The objective of study is to determine the optimal LP content for HPC matrices and assess the flexural behavior of T-girders cast with HPC using limestone powder. Testing HPC matrices involved exploring three LP-to-cement ratios (0, 10, and 20% by mass). Three T-girder types were examined: HPC girder with main rebars and stirrups (G1), HPC girder with only main rebars and no stirrup (G2), and HPC girder without reinforcement (G3). Results indicated that the optimal LP content for achieving the highest compressive strength in the HPC matrix was 10% by mass of the cement. In T-girders, G2 exhibited higher flexural resistance by 13.5% and 63.0% compared to G1 and G3, respectively. G3 without reinforcement demonstrated the lowest flexural resistance. In conclusion, the T-girder cast with HPC using LP and featuring only main rebars (G2) proves applicable to practical transportation works. This research signifies a pioneering step towards sustainable and high-performance infrastructure development in bridge construction.