## 1 Introduction  
Superannuated nuclear energy facilities should be decommissioned worldwide; however, these facilities are expected to increase gradually [1]. According to the International Atomic Energy Agency (IAEA), as of February 2023, there were 423 nuclear power plants in operation, 204 facilities were permanently shut down, and the dismantling of 25 facilities was completed [2]. When decommissioning nuclear facilities, hundreds of thousands of tons of waste are generated, and it has become a pending global issue to guarantee technologies for their reduction and recycling [3]. For this reason, advanced countries such as Germany, the USA, Belgium, and Japan have consistently conducted research on the development of treatment technologies for waste generated from nuclear decommissioning facilities [4, 5]. In addition, some countries have already secured superior nuclear decommissioning technologies, including decontamination, reduction, and recycling of nuclear waste [6, 7, 8]. Nuclear power facilities have reinforced concrete structures, and a considerable amount of waste, such as cementitious waste, coarse and fine aggregates, waste soil, and metal waste, is generated from the process of decommissioning them [9, 10]. In addition,according to a report by the European Commission (EC), 5 million tons of concrete waste (CW) are expected to be generated from the decommissioning process in Europe until 2060 [6]. Most CW is classified as ultralow-level radioactive waste, constituting approximately 60-80% of the total waste [11; 12]. Aggregate and cement powder can be separated from CW using thermal and mechanical treatments, and the aggregate is generally fractionated into recycled coarse and fine aggregates based on the size of 5 mm [13]. During the crushing, grinding, and separation processes of CW, powder is generated, which consists of constituents originating from the cement paste as well as fine aggregate [14]. This powder contains many inorganic substances, such as calcium silicate hydrate (CSH), calcium hydroxide (CH), and SiO\({}_{2}\), which are effective materials for waste treatment. Therefore, the powder can be used for recycled cement (RC) after crushing and burning more than twice [15]. Accordingly, instead of disposing of the powder, it is utilized as a solidifying agent for RC, leading to a decrease in the usage of common solidifying agents, such as Portland cement, as well as reducing the amount of waste and cost of disposal [16]. In addition, waste soil is generated from the decommissioning process, and it contains some clay minerals, such as illite and zeolite, which show an excellent capacity for adsorbing radioactive nuclides. Hence, if waste soil can be used as an adsorbent, not only is the amount of radioactive waste reduced, but safe disposal is also ensured [17]. Research on the application of concrete waste powder (CWP) originating from the decommissioning process to RC has been conducted continuously since 2000. However, it remains problematic that it shows insufficient compressive strength and an unbalanced chemical composition due to the constituents originating from fine aggregates [18; 19]. Therefore, there is a need to focus on the separation of waste cement powder from fine aggregates. To compensate for this problem, some studies have been conducted to improve the RC quality by blending cementitious waste powder with industrial by-products, such as blast furnace slag (BFS) and fly ash (FA), which are used as cement admixtures (adjusting agents) to increase their compressive strength [20; 21; 22]. BFS can improve the compressive strength of RC as a result of the hydration reaction because it has a 30% CaO content and can be used as a substitute for ordinary Portland cement (OPC) [23]. However, BFS exhibits potential hydraulicity (hydraulic properties), and the addition of alkaline reagents is required for hydration [24].