## 1 Introduction  
Over the past two decades, rapid urban population growth has led to an intensification of construction and demolition activity [1]. In order to satisfy this increasing demand, the built environment has relied on concrete as its primary manufactured material due to its affordability, versatility, and high strength [2]. Currently, concrete is the most widely used manufactured material, and is extensively employed in structural and non-structural elements [3]. However, the concrete production process has a significant carbon footprint, since it emits approximately 850 kg of CO\({}_{2}\) per ton of clinker produced and requires substantial natural resources [4]. The current practices of the concrete industry are at odds with the objectives set forth by the European Commission (EC), which aim for a reduction of Greenhouse Gas (GHG) emissions of at least 55% by 2030 and a net zero scenario by 2050 [5]. The European GreenDeal [5] and the Circular Economy Action Plan [6] established practices to minimise landfill and enhance material recovery by emphasising the importance of designing for durability, reparability, and recyclability [7]. However, fulfilling these initiatives relies on the effective transition to a Circular Economy (CE) model [8]. This regenerative economic system promotes the closed-loop flow of goods through reuse, thereby producing secondary raw materials or serving other purposes. Such practices prevent further resource extraction, optimise material usage, and foster the regeneration of natural systems [9; 10; 11]. The CE, therefore, encourages sustainable development by acknowledging the interconnectedness of ecological stewardship, social development, and economic growth [12; 13; 14]. The International Energy Agency (IEA) [15] recommends that the concrete industry improve energy efficiency and incorporate alternative fuels and raw materials to align with the net zero scenarios. As a response, several studies have focused on replacing traditional production fuels with biomass or other types of waste [16]. Additionally, research has focused on enhancing the efficiency of Construction and Demolition Waste (CDW) treatment and reuse, such as through the combined use of dark fermentation in Moving Bed Biofilm Reactors and the bioleaching of concrete debris [17]. Other strategies aimed to reduce resource extraction by including supplementary cementitious materials [18], developing more durable or self-healing concrete [19; 20; 21], utilising higher-strength concretes [22; 23; 24], capturing and storing CO\({}_{2}\) emissions [25; 26; 27], and incorporating Recycled Aggregates (RA) in concrete production [28; 29; 30; 31]. Recycled Aggregate Concrete (RAC) is an innovative material obtained from crushed, screened, and washed RA derived from discarded concrete [32]. It has significant cost-effective potential for the reduction of GHG emissions since the Natural Aggregate Concrete (NAC) mixture usually consists of approximately 70% to 80% aggregate by volume [33]. The EC is interested in using RAC to optimise the 850 million tonnes of CDW generated in the European Union (EU) annually [34], thereby contributing to the annual demand for 2.55 billion tonnes of aggregate [35]. However, certain studies [28; 36] highlight that the mechanical properties of RAC are approximately 10% to 20% lower than those of NAC. This disparity is attributed to the adhered mortar [37] and micro-cracks formed during the recycling or recovery process [38]. Consequently, the water absorption of RAC is approximately ten times greater than that of NAC, while its bulk density is reduced by about 22% [39]. Furthermore, the compressive, splitting, and flexural properties of RAC are diminished by 9.25%, 18.5%, and 17.6%, respectively [40]. Axial compression, shear resistance, and bond strength are also 6% to 24% lower than that of NAC [41]. International standards have considered these findings and have established requirements for RA, particularly in structural applications [42].