Concrete is one of the most important construction materials used in building and infrastructure projects. Its production primarily depends on natural aggregates, the extraction of which requires continuous consumption of natural resources and causes various environmental impacts. With the increasing quantities of construction and demolition waste, it has become necessary to explore effective methods for recycling these materials and utilizing them in the production of sustainable construction materials. The use of recycled aggregate obtained from crushed old concrete is considered a promising solution for reducing the consumption of natural aggregates and minimizing the environmental impacts of the construction industry. This study aims to evaluate the mechanical performance of concrete produced using recycled aggregate by investigating the effect of replacing natural aggregate with different percentages of recycled concrete aggregate. Several concrete mixtures can be prepared using replacement percentages of 25%, 50%, 75%, and 100%, in addition to a reference mixture containing only natural aggregate. This approach allows for comparison and assessment of the influence of different replacement levels on concrete properties. The study focuses on investigating the mechanical properties of concrete, particularly compressive strength, splitting tensile strength, and flexural strength, as essential indicators for evaluating its performance in structural applications. Additional tests can also be conducted to determine density, water absorption, and workability. Concrete specimens can be tested at different curing ages, such as 7, 28, and 56 days, to monitor strength development over time. The properties of recycled aggregate depend on the source of the concrete waste, crushing and processing methods, and the amount of old cement mortar attached to the aggregate surface. Recycled aggregate generally exhibits higher water absorption and porosity than natural aggregate due to the presence of adhered old mortar and microcracks. These characteristics may negatively affect the workability and mechanical strength of concrete. Therefore, pretreatment processes, such as cleaning, washing, and removing impurities, as well as controlling the moisture content of the aggregate, may contribute to improving its performance in concrete mixtures. It is expected that increasing the percentage of recycled aggregate may lead to a gradual reduction in some mechanical properties of concrete, particularly compressive strength, due to its higher porosity and the weaker interfacial transition zone between the aggregate and cement mortar. However, the results may vary depending on the quality of recycled aggregate, replacement percentage, mix design, and curing conditions. Nevertheless, certain replacement percentages may achieve acceptable structural performance, making recycled aggregate suitable for specific applications that do not require high strength, provided that the resulting concrete complies with the relevant standards. The significance of this study lies in the possibility of utilizing concrete waste generated from demolition and construction activities and converting it into an alternative source of natural aggregate. This approach contributes to reducing the depletion of natural resources, decreasing the amount of construction waste sent to landfills, and minimizing the costs associated with waste transportation and disposal. Furthermore, it supports circular economy principles and promotes the implementation of sustainability practices in the construction sector. In conclusion, the use of recycled aggregate in concrete production represents an important step toward developing sustainable construction materials. Achieving the required mechanical performance requires investigating suitable replacement percentages and evaluating the effects of aggregate properties and pretreatment methods on concrete strength and durability. This will help determine the feasibility of using recycled aggregate in various structural applications while achieving a balance between engineering performance, environmental sustainability, and economic efficiency.