## 2 Materials and Methods
### Characterization of FM Adnixtured Mortars
#### 3.1.2 Impact of Alkaline Conditions on FM  
Apparent viscosity: When the nucilage is dissolved in the mixing water, the pectic and neutral fractions interact and structure themselves to form a more or less viscous network, depending on the concentration. This viscosity was therefore determined at different nucilage concentrations and is used as a reference for determining the quantity added to the cementitious matrix. It is also possible to simulate the effect of the cementitious matrix on the composition and/or degradation of polysaccharides using viscometry. The viscosimetric behavior of polysaccharides dissolved in different alkaline solutions (NaOH and Ca(OH)\({}_{2}\)) with a deliberately high pH, such as the cementitious medium, can be seen in Figure 1.  
Firstly, Figure 1 shows that the viscosity of the FM increases significantly as a function of the FM concentration. This increase is accelerated at around 15 g/L. This concentration was identified as a gelling point or a sol-gel transition [25]. [PERSON] [25] conducted a study on the viscous properties of FM and found that FM exhibits shear-thinning behavior. This means that the viscosity increases with increasing polysaccharide concentration, primarily due to interactions between the two distinct fractions present in FM. The pectic fraction that is anionic has minimal or no impact on determining the solution's physicochemical properties. Instead, it is mainly the neutral fraction, primarily composed of AX, that is responsible for the exceptionally high viscosity of the nucilage solution. The gel-forming characteristics of the AX solution arise from intermolecular hydrogen bonds and a relatively larger molecular weight compared to the acidic fraction. Several studies have reported \begin{table}
\begin{tabular}{c c c c} \hline
**Monosaccharide** & **HPAEC-PAD FM (Raw) 1** & **FM 3** & **OFI 4** \\ \hline Xylose & 15.640 \(\pm\) 0.984 & 34.67 & 1.1 \\ Glucuronic acid & 0.009 \(\pm\) 0.003 & 0.020 & 23.2 \\ TOTAL & 45.105 \(\pm\) 1.793 2 & 100 & 100 \\ \hline \end{tabular} 1 Raw data obtained from the HPAEC-PAD. 2 The sum of compounds does not reach 100% due to carbohydrates losses during the HPAEC-PAD hydrolysis [26]. 3 First column monosaccharides content on 100% basis to compare with OFI. 4 Values from [PERSON] et al. [27].  
\end{table} 
Table 2: _Cont._  
Figure 1: Apparent viscosity of FM solutions at 20 \(\pm\) 2 \({}^{\circ}\)C (60 rpm). a critical transition point in the apparent viscosity of the mucilage solution [4; 25]. Like many plant extracts [28; 29], this sol-gel transition point corresponds to the concentration or condition at which the solution ceases to be considered a true solution and instead behaves as a gel. This transition occurs due to the increasing entanglement of polymeric chain networks, which restricts the mobility of the polysaccharide chains and leads to a significant increase in viscosity [25]. FM does not exhibit the same behavior when added in alkaline conditions, as shown by the Figure 1. The viscosity curves part ways with the aqueous medium from a 5 g/L concentration. The apparent viscosity increases with the concentration but much less for the alkaline solutions than in water. There are two possible explanations for these observations. First, the intermolecular network formed by hydrogen bond is reduced due to the action of NaOH and Ca(OH)\({}_{2}\) solutions. [PERSON] et al. [30] worked on the gelation properties of flaxseed gum and confirmed the results shown in Figure 1. Flaxseed gum is characterized by its anionic polysaccharide nature, resulting from the presence of ionized carboxyl groups that generate a negative charge. The electrostatic forces between like-charged molecules cause the molecular chains to fully extend and intertwine, facilitating the formation of intermolecular cross-links that induce gelation at pH between 6 and 9. The authors explained that increasing the pH above 9 diminishes the gel strength and thus the apparent viscosity.