The city of Mosul in Iraq witnessed massive destruction during the war against ISIS, leaving behind large amounts of rubble and concrete resulting from demolition operations. The concrete can be converted into rubble and replaced with natural rubble. Replacing the natural aggregate in the concrete with a recycled aggregate of the reused concrete exposed to demolition. This process is considered in the field of sustainable construction and an environmental and economic solution. It works to reduce the use of natural resources, preserve them, and get rid of waste resulting from the demolition of concrete. The main objective of this research is to develop and improve concrete mixtures and use recycled aggregate as an alternative to natural aggregate. Moreover, to eliminate the environmental impact and reduce the depletion of natural resources. Special focus was placed on the physical properties of modified concrete when the natural aggregate was replaced by recycled aggregate in different proportions starting from 25%, 50%, 75%, and 100% of the natural aggregate. Studies have shown that using 25–50% recycled aggregate maintains the mechanical properties of concrete, approximating those of natural aggregate. The compressive strength results were 9.2% lower than the reference mix and the flexural strength was 6.5% lower than the reference mix. Using recycled aggregates in concrete at levels greater than 50–100% resulted in further reductions in compressive strength, flexural strength, workability, absorption, and density.