Concrete is a widely used construction material; however, its performance can be significantly affected by the quality and characteristics of the aggregates used. In recent years, interest in utilizing recycled and waste materials has increased. The benefits of such materials include enhancing concrete properties and promoting sustainability. This paper presents an experimental study of the mechanical properties of polymer modified concrete by utilizing waste gabbro as a coarse aggregate replacement. Styrene Butadiene Rubber (SBR) was used as a polymer modifier in the concrete mix at 10% of the cement weight, and the superplasticizer Flocrete PC200 was added at 1% of the cement weight. The study evaluates key mechanical properties including, compressive and tensile strength at 28, 60, and 90 days. Five replacement ratios of gabbro were tested: 0%, 25%, 50%,75%, and 100%. The effect of freeze-thaw cycles on concrete mixes was also examined. The findings indicate that substituting traditional aggregates with gabbro rock enhances the mechanical properties of the concrete and improves its residual strength after exposure to freeze-thaw cycles.