<p>Although there are ongoing studies on innovative green materials, building materials are mostly composed of cementitious compounds as binders. Cement is known to significantly increase CO₂ emissions both during its production and utilization. Furthermore, while the utilization of industrial by-products in waste storage and disposal processes offers positive contributions to the circular economy, this approach does not constitute a holistic and adequate solution in terms of the environment and human health. This study presents the results of the effect of mud powder obtained from Rize province on the mechanical and microstructural properties of cement mortars to the academic environment. The mud was dried and ground, then calcined at 600, 700 and 800&#xa0;°C. The calcined mud powder obtained at the optimum calcination temperature was substituted into cementitious mortars at 0%, 10%, 20%, 30% and 40% by weight. The parameters used in the study were material/ball weight = 1/12 and binder/cement weight = 0.45. Compressive and flexural tests were performed for mechanical strength and XRD, SEM–EDS, FTIR, Specific gravity, and UPV tests were performed to explain the microstructures. The numerical and test data imply that the maximum 28-day compressive strength of 46. 65&#xa0;MPa was obtained as a result of 10% substitution of calcined mud powder, which is a natural resource. These results indicated that calcined powder mud (CPS) has strong potential as a sustainable material for construction and structural applications.</p>