الكتابة Mechanical Behavior of Concrete Incorporating Waste Tire Rubber: Effects on Compressive and Flexural Strength Presented by: Asst. Prof. Dr. Mayada Waheed Fallah Head of the Civil Engineering Department – Al-Mustaqbal University As part of ongoing efforts to promote environmental sustainability and develop eco-friendly construction materials, the use of waste tire rubber in concrete production has emerged as a modern approach in materials and construction engineering. This approach aims to reduce the environmental impacts associated with the accumulation of waste tires by recycling them and using them as a partial replacement for natural aggregates in concrete mixtures. This contributes to conserving natural resources and improving waste management efficiency. This topic focuses on investigating the mechanical behavior of rubberized concrete, also known as Rubcrete, with particular emphasis on the effects of different rubber replacement ratios on compressive and flexural strength, as well as the changes in its mechanical and physical properties. Engineering studies indicate that incorporating rubber into concrete mixtures influences the way concrete responds to applied loads. It can improve ductility, energy absorption capacity, and impact resistance while reducing the sudden and brittle failure characteristic of conventional concrete. This behavior is associated with the flexibility of rubber and its significantly lower modulus of elasticity compared with natural aggregates, allowing rubberized concrete to withstand relatively greater deformations before final failure. Regarding compressive strength, increasing the proportion of rubber used as a replacement for aggregates generally leads to a reduction in strength. This is mainly attributed to the weak bond between the rubber surface and the cement paste, in addition to the substantial differences in stiffness and modulus of elasticity between the two materials. Nevertheless, controlling the replacement ratio, rubber particle size, and concrete mix design can help achieve an appropriate balance between mechanical strength and the flexible properties of concrete. In terms of flexural strength, rubberized concrete exhibits behavior that differs from that of conventional concrete. Although its maximum flexural strength may decrease, its ability to withstand deformation and absorb energy after the formation of initial cracks may improve. This behavior helps reduce sudden failure and enhances the concrete's ability to respond to dynamic loads and impacts, depending on the type of rubber, its replacement percentage, and the characteristics of the concrete mixture. Rubberized concrete is also characterized by relatively lower density and an enhanced capacity to absorb vibrations and impacts. These properties make it a promising material for certain engineering applications, including impact-absorbing highway barriers, floors subjected to vibrations, and selected pavement elements used in environments where noise and vibration reduction is required. This topic highlights the importance of conducting a comprehensive evaluation of the mechanical properties of rubberized concrete before adopting it in structural applications, while taking into account the strength, safety, and engineering design requirements of each application. The successful use of recycled rubber depends not merely on improving a single property, but on achieving a balance among load-bearing capacity, ductility, durability, and environmental sustainability. In conclusion, incorporating waste tire rubber into concrete production represents an important step toward developing more sustainable construction materials by combining waste recycling, reduced consumption of natural aggregates, and the beneficial use of rubber's flexible properties. This approach also opens promising research opportunities for engineers and researchers to develop concrete mixtures that achieve suitable performance and meet the requirements of modern engineering applications, thereby supporting innovation and sustainability in the construction industry.