## 2 Materials and Methods  
### Constituent Materials  
FTB mixtures were prepared in the laboratory by employing two quartztite aggregate fractions (0-8 mm and 8-14 mm), two different types of sawing sludge (indicated as \"A\" and \"B\"), CEMII/A-L R42.5 cement Cemem (1998), water, and a polycarbonate-based superplasticizer. According to the information obtained from the supplier, both aggregate fractions were reported to have a quartz content of the order of 95%. They were selected to form the bulk structure of the FTB mixtures, since quartzite is the metamorphic rock with the highest thermal conductivity Cem (1998); Cem (1998). The two types of sludge were retrieved from cutting plants located in the north-west of Italy, where they were being stockpiled before disposal. General information on the origin, composition, and generating cutting technology of the two types of sludge is listed in Table 1.  
Preliminary analysis of aggregate fractions and sludge included the determination of particle size distribution and specific gravity (SG) as per corresponding EN standards S. S.  
Since contamination from heavy metals was expected due to the wear and tear of cutting tools, sludge was subjected to chemical analyses and leaching tests. Chemical analyses were performed on dried samples of sludge by means of an inductively coupled plasma (ICP) mass analyzer (as per [38]). Then, test samples were subjected to leaching tests carried out in accordance with EN 12457-2 [39], with the consequent determination of the heavy metals content of the leachate solution by means of the previously mentioned ICP mass analyzer. Finally, a supplementary quick assessment of the quantity of metals present in the two types of sludge was performed by following the procedure described in [PERSON] et al. [24], which was based on the use of a  
As shown in Figure 1, it was observed that both types of sludge were characterized by a very fine particle size distribution, which qualifies them as good candidates for inclusion in FTBs. In fact, in order for FTBs to exhibit a self-compacting and self-leveling behavior, it is necessary to include in their formulation a relevant amount of fines [15]. Test results contained in Table 2 indicate that the SG determined for the quartzite fractions was consistent with data reported in literature, which refer to a typical range of \(2.6\div 2.8\)[42]. However, significant differences were recorded when comparing the SG values of the two types of sludge, thus confirming their different origin in terms of mineralogical composition and cutting operations. With respect to composition (Table 3), it was found that sludge B contained a greater amount of quartz in comparison to sludge A. This is a consequence of the different quartz content of the rocks from which they were derived: of the order of 50% for silicate rocks (that yielded sludge B) and of approximately 20% for Serizzo stone (corresponding to sludge A). The significant difference in the composition and origin of the two types of sludge were also reflected by the results of chemical analyses and leaching tests (Tables 4 and 5, respectively) that focused on the presence of heavy metals. As indicated in Table 4, sludge A showed higher contents of Ni, Cu, and Fe, which come from employed gangsaw cutting tools, while sludge B was characterized by higher contents of Zn, Co, Pb, and Cr\({}_{\text{tot}}\), which was probably as a consequence of the diamond blade and diamond wire technologies used during processing operations. By comparing the concentration of heavy metals of both materials with the threshold limits established by Italian legislation for use in industrial and commercial areas [38; 40; 43], it was observed that only the concentration of Cr\({}_{\text{tot}}\) of sludge B exceeded the prescribed limit. In any case, it should be underlined that the above-mentioned legal limits refer to the use of materials in their raw form, which is not the case of the sludge considered in the study described in this paper.