## 1 Introduction
Nevertheless, some of them react in alkaline environments leading to the well-known alkali-silica reaction (ASR) [12], which is a deleterious process ocurring between the amorphous silica present in the reactive aggregates [13] and the alkaline constituents of the pore solution, such as sodium, potassium, and hydroxyl ions, among others [14]. A hydrated ASR gel is the reaction product, which can imbibe water and swell when enough reactive silica, alkali content and moisture are present in the system. Accordingly, the internal swelling pressure promotes expansion of the cement-based material, cracking and loss of mechanical strength and durability in concrete structures. [PERSON] et al. reported three types of cracks in the inner region i.e., isolated cracks without ASR gel which appear in the cement the paste or in the aggregate grains or at the aggregate-paste interface (type 1); cracks in aggregate grains filled with ASR gel (type 2); and cracks without ASR gel linked to type 2 cracks that are formed in the paste or at the interface [15]. Understanding the mechanism of the ASR has practical implications, of to propose potentially preventive measures to minimize ASR impact. ASR occurs between the reactive silica present in the reactive aggregates and the alkaline pore solution of concrete. The main sources of alkalis are the Portland cement, fine and coarse aggregates and the surrounding environment. These alkalis with water form soluble alkali hydroxides [14]. Normally, the silica in the form of quartz is chemically inert. Nevertheless, poorly crystalline silica, present in opal, chert, chalcedony and so on, reacts with the pore solution to form amorphous hydrous silica. ASR proceeds according to the following steps [14]. Firstly, siloxane bonds (Si-O-Si) breakup by hydroxyl ions is produced to generate alkali silicate gel and silicic acid (silanol bonds). Afterwards, alkali-silica gel moves from aggregate to cement paste and reacts with the calcium ions forming alkali-calcium silicate hydrate gel. Secondly, alkali-silica gel imbibes water from the surroundings and swell leading to an increase of the internal swelling pressure and material expansion, which may produce aggregate and cement paste cracking and concrete damage. Recently, the use of construction and demolition wastes (CDW) and recycled aggregates (RA) has become a topic of great interest in the circular economy context [16; 17]. It is suggested that the possibility of having potentially reactive aggregate will be increased using RA [17]. Potential preventive measures to avoid the ASR include the use of blended cements made with adequate pozzolans [18; 19; 20; 21; 22] or low-alkali cements, reactive aggregate beneficiation [23], optimize the structural design to avoid the concrete wetting and so on. All of them can be considered as levers to achieve the expected concrete mix design improvement and their effectiveness depends on the reaction mechanism and its intensity. In addition, the current widespread use of blended cements in the construction industry finds its recent promotion in the challenge to meet the target of holding temperature rises to 1.5 \({}^{\circ}\)C by the end of the 21 st century [8]. Pozzolanic additives contain a certain content of alkalis, however, it has been reported that blended cements control ASR expansion because they are able to bind alkalis and to limit the further availability for reaction with reactive aggregates [24; 25]. Accordingly, ASR mitigation effectiveness is dependent on the chemical composition of the blended cement. Alkalis are present in the pore solution or bound by the blended cement hydration products or added to ASR gel. Therefore, the chemical characteristics of the addition present in the binder and replacement level will influence the pore solution concentration. Such additions lower the alkali-hydroxides concentration in the pore solution of concretes [25; 26; 27; 28]. The higher replacement level is, the lower concentration was monitored.