## 2 Materials and Methods
### Characterization of FM Adnixtured Mortars
#### 3.1.2 Impact of Alkaline Conditions on FM
Furthermore, they also mentioned that the Na\({}^{+}\) action on the zeta potential leads to a decrease in the intramolecular charge repulsions. The same mechanism of electrostatic repulsion exists with a large amount of divalent cations like Ca\({}^{2+}\), which inhibits the formation of a three-dimensional network [30]. The presence of divalent cations in a lower concentration can, however, induce a cross-linking or flocculation of the polysaccharides, as we observe a sedimentation because of agglomerates' formation. These phenomena are visible in Figure 1, as the NaOH and Ca(OH)\({}_{2}\) solution curves flatten compared to that for water. A higher flattening on the Ca(OH)\({}_{2}\) curve can be evidence of a divalent cation intermolecular cross-linking, shown by a flocculation visible during the material preparation. The second hypothesis that can lead to the apparent lowering of viscosity concerns the possibility of polysaccharide degradation. In our conditions, molecular weight determination by SEC-MALS analysis does not demonstrate backbone hydrolysis (Figures S1 and S2). This hypothesis is not consistent with our results. Thus, in NaOH and Ca(OH)\({}_{2}\) solutions, the decline in gel strength is linked to fewer junction zones due to high pH levels (pH > 9) and the presence of monovalent and divalent cations, as reported by several authors [31; 32; 33]. Compositional modifications--FTIR: The FM solubilized under different conditions were analyzed in FTIR to determine possible compositional modifications. The FTIR spectra are visible in Figure 2. First, there is an appearance of a doublet at 897 and 866 cm\({}^{-1}\) when alkaline conditions are applied to the FM. These bands are characteristic of the co-existence of \(\beta\)- and \(\alpha\)-glycosidic bonds [34], respectively. This new co-existence is possible evidence of an alkaline hydrolysis, as alkaline catalysts are often used to liberate carbohydrate chains from glycoconjugates [35]. The liberation of glycoconjugates such as proteins is visible on the NaOH solution spectrum with the disappearance of the N-H bond at 1541 cm\({}^{-1}\). Also, the C-H \"hairy zone\" and -CH\({}_{2}\) branched at 1413 cm\({}^{-1}\) look different. The increase in the band and the apparition of a triplet at 1444, 1413, and 1382 cm\({}^{-1}\) seem to confirm the hydrolysis of the side-branched conjugates. In the Ca(OH)\({}_{2}\) FM solution, this N-H bond seems to still be present, as the divalent cation can bind different polysaccharide/protein compounds and then limit the impact of alkaline solution as characteristic groups are protected. The complexification and increase in organic species present in the cementitious medium after the FM degradation make it more complicated to conduct studies and to identify the mechanisms intrinsic to the initial polysaccharides. For example, [PERSON] et al. [36] related that xylose, which is the main saccharide of the FM, degrades mainly to formic acid and furfural. [PERSON] and [PERSON] [37] described the alkaline degradation process of polysaccharides as a peeling process in which the reducing end-group is liberated from a chain by elimination of the rest of the chain as a glycox anion.