Today, only a very small portion of plastic waste is recycled, while huge quantities remain untreated and are becoming increasingly worrying. The search for other alternatives is still an urgent necessity so that these wastes can be reduced to the maximum; their valorization may be the best solution. This study concerns a new technique for the valorization of polyethylene terephthalate (PET) plastic bottle wastes, in order to design a composite material, i.e. siliceous sand-PET, which then gives a Waste Plastic Lightweight Aggregate “WPLA”. Our hope is to provide solutions to specific and general applications in the field of construction. Some observations are noted on the effects of this composite on destructive and non-destructive testing, such as the physical properties and mechanical behaviors of an industrial composite screed, by substituting 0, 25, 50, 75 and 100% by weight of natural aggregate by this composite. Scanning electron microscope (SEM), FT-IR and X-ray diffraction analyses were used to better understand the cement hydration products of the composite mortars. Some possible uses of this screed, or even of the composite itself, can subsequently be recommended. Encouraging results were obtained regarding the usage of this composite aggregate as an eco-material in the field of construction for sustainable development. In addition, it provides environmental-friendly and cost-effective solutions in using recycled materials for concrete construction applications.