In case of simply supported reinforced concrete beam, the portion above neutral axis is in compression and the portion below neutral axis is in tension. Tension and compression on the neutral axis is zero. Concrete takes compressive stress and steel takes tensile stress, so concrete below neutral axis is not necessary. Plastic waste is increases day by day and this waste we can’t burnt and dispose so reuse of plastic us very essential. In this project we fully replace coarse aggregate by recycled plastic aggregate below the neutral axis of beam and we take flexural test on RC beam. Due to rapid growth of industries and due to urbanization in the country it leads lot of infrastructure. So that it leads to many problems like lack of construction material, increased productivity of wastes and other products. This project deal with the reuse of recycled plastic waste as partial replacement of natural coarse aggregate in M20 grade concrete and usually M20 grade concrete is used for most constructional works.