## 1 Introduction  
According to data presented by the United Nations, in 2015 the world population was about 7.3 billion, and was expected to reach 9.7 billion by 2050 [1]. The same report also indicates that in 2015, for the first time, the majority of the world's population was living in cities. Migration of populations to urban areas has benefited global development, but the urban pressure in these areas implies a significant increase in built-up area, with an increase in the production of construction and demolition waste (CDW), whose environmental impact is extremely negative. The constitution of the CDW depends, for instance, on the origin of the waste, on the time it was collected and on the type of construction which gave rise to it. According to [PERSON] [2], CDW is the most heterogeneous of industrial wastes. Taking into account that a building consists of dozens of distinct elements, it is not surprising that the waste resulting from the demolition of a given construction will have a heterogeneous composition. [PERSON] et al. [3] further highlighted other factors that explain the heterogeneity of CDW coming from a given construction site: the level of technical development of the construction industry, the quality of labour available, the construction and demolition techniques used, the recycling and reuse processes defined and the materials available. The European Union has set some targets for the reduction, reuse and recycling of CDW by means of Directive 2008/98/EC, which defines that, by the year 2020, 70% of the CDW produced annually must be recycled [4]. In 2010, according to [PERSON] et al. [5], the percentage of CDW sent for recycling in the European Union was only 47%. Today, despite all technological developments, reinforced concrete still remains the most widely used structural material in the world. However, if it is generally agreed that this material has several advantages, it is also true that concrete carries with it a serious problem: a high ecological footprint. This problem has to be solved/minimized urgently so that the construction sector can become sustainable. The production of concrete involves the use of natural aggregates (sand and crushed stone), which, since they are non-renewable materials, give rise to significant environmental impacts. The geological impacts caused by the extraction of sand, such as the alteration of the ground and coastlines and the visual impact, are some of the most significant [6]. It should also be noted that the production of aggregates, due to the energy required for their generation, accounts for about 15% of the total CO\({}_{2}\) emissions resulting from the production of concrete [2]. Hence, one of the environmental improvements that has been studied is the incorporation of several waste products in the production of concrete. This measure results in a decrease of the natural resources consumed by the concrete industry and reduces the amount of waste deposited in landfill, both of which have beneficial effects for the environment. It should be highlighted that the European Commission identified CDW as a priority waste stream for treatment and recycling since high quantities are produced and due to its high potential for reuse as a raw material [4]. Thus, it is not surprising that, in recent years, several investigations have been carried out to evaluate the use of CDW in concrete [4]. The properties of concrete with recycled aggregates made of concrete, ceramic materials, glass or plastics, among others, have been analysed in order to understand their potential and limitations. However, research on the use of CDW from recycling plants in concrete is still limited [7]. Most previous studies dealt with the use of a single type of recycled aggregates (RA) from CDW, overlooking the need for comparing different CDW with distinct compositions. On the other hand, there are also few studies that exhaustively analyse the RA used in concrete, by means of composition analysis and physical and chemical tests.