Marble is a metamorphic rock and one of the most important decorative building materials. About 20-30% of a marble block becomes marble powder throughout the cutting process. Marble powder is harmful to human health and to the environment. The main purpse of this research is to study the microstructural characteristics and properties of hardened concrete made with WMP as partial replacement of cement. The main variables in this research are the percentage of marble powder (0, 5, 10, 15, 20, 30, and 40% ) as a partial replacement of cement content in concrete mixes and the age of testing (7, 28, and 56 days). Hardened concrete properties are driven in terms of compressive, splitting tensile, flexure modulus, and bond strengths. Also, the modulus of elasticity of different mixes was measured and microstructural scanning by an electronic microscope was carried out. The microstructural analysis was conducted on concrete matrix densification, attributed to pores refinement due to both physical and chemical changes in the concrete matrix. The results showed that replacing cement by 10% of marble powder increased the strength and improved the concrete microstructure.