Composite materials in the context of cement and concrete refer to engineered combinations of two or more materials with differing properties to achieve superior overall performance. These composites typically involve the incorporation of fibers (such as steel, glass, or carbon), particulates, or other additives into the concrete mix to enhance its mechanical properties, durability, and resistance to environmental stresses. The mechanism behind composites in concrete involves the effective load transfer between the matrix (cement paste) and the reinforcement (fibers or particulates), which improves tensile strength, crack resistance, and energy absorption capabilities of the concrete.