<p>In recent decades, the impact of human activity as an agent of environmental degradation has driven a growing demand for sustainable materials, encouraging research into alternative materials with lower environmental impact. This study aims to investigate the effects of adding residual rock powders from the crushing of basalt, basaltic andesite, and dacite, minerals characteristic of the Serra Geral Formation, on the rheological and mechanical performance of cement mortars. These three rock powders, with different silica contents, partially replaced cement at levels of 5%, 10%, and 15% by weight. Compressive and tensile strength tests were carried out to evaluate the mechanical performance of the samples. In addition, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), consistency index measurements, and particle size analyses were conducted. The experimental results show that the addition of rock powders increases the consistency index but, in some cases, reduces mechanical strength depending on the chemical composition of the rock. Among the mixtures, dacite showed the best results in terms of improving consistency, and the 10% replacement level provided the best balance of improved workability without significant loss in mechanical strength for both basaltic andesite and dacite. Furthermore, the 15% replacement level appeared to delay the hydration process of the cement particles. Therefore, the use of rock powders in mortar mixtures proves to be an effective method for enhancing consistency while promoting the recycling of industrial mineral waste.</p>