The re-use of construction and demolition wastes (CDW) in concrete production gathers increasing interest in order to minimize the environmental footprint of the building industry. However, although its positive environmental impact seems evident, ambiguous literature data regarding the quality and safety aspects, raise doubts about CDW upcycling. The controversy seems to arise from the different materials and methods of construction and demolition used. Therefore, in order to reach an informed decision on whether concrete made using CDW can be usable, it is necessary to consider its physical, chemical, and mechanical properties and compare its technical and environmental performance to that of conventional concrete, taking into account specific materials and methods of construction.