This study presents an experimental investigation of the mechanical properties of concrete incorporating Kadapa Marble Powder (KMP) as an additional cementitious material. It focuses on varying the content of KMP (ranging from 0% to 15% by weight of cement) and conducting tests on compressive strength, modulus of elasticity, and creep. The replacement of cement with KMP led to improvements in the compressive strength and modulus of elasticity, and the incorporation of KMP contributed to a reduction in the creep phenomenon of concrete over time. The beneficial effects of KMP can be attributed to its ability to react with calcium hydroxide generated during cement hydration. This reaction results in the production of additional calcium silicate hydrate, which fills voids and large pores within the concrete matrix. As a result, the porosity associated with the capillary pores and voids decreased. This observation was supported by the examination of the microstructure of hardened concrete using scanning electron microscope techniques. The presence of KMP enhanced cement hydration and contributed to a reduction in the porosity associated with the gel pores. This was attributed to the release of absorbed water retained in the small pores of the KMP particles. This study highlighted the potential of incorporating KMP as a beneficial cementitious material for concrete production. These findings suggest that KMP can enhance the mechanical properties of concrete, including the compressive strength and modulus of elasticity, while mitigating the creep phenomenon. The analysis also provides insights into the microstructural changes that occur in concrete due to the inclusion of the KMP.