## 2 Materials and Methods
The proportions of the alkali-activator solution, alkali dosage, and silicate modulus (Ms) are given in Table 2. The formulation's optimal stoichiometry was determined after carrying out a preliminary study to delimit the proportion of raw materials and to obtain the best mechanical performance of AA-WBA binders cured at room temperature. The same amount of WBA, NaOH, and Na\({}_{2}\)SiO\({}_{3}\) solutions (referred as liquid; L) were used in each formulation. The concentration of the NaOH solutions (2, 4, 6, and 8M) was varied to evaluate its effect on the AA-WBA final properties and structure of the cementitious matrix. The concentrations of NaOH were chosen considering the previous studies carried out by the authors [41]. \begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline \hline  & & & & & & & & & & & \\ \hline
**SiO\({}_{2}\)** & **CaO** & **Al\({}_{2}\)O\({}_{3}\)** & **Na\({}_{2}\)O** & **K\({}_{2}\)O** & **Fe\({}_{2}\)O\({}_{3}\)** & **MgO** & **TiO\({}_{2}\)** & **Cl\({}^{-}\)** & **SO\({}_{3}\)** & **1 LOI** \\ \hline
45.44 & 17.55 & 10.38 & 5.04 & 1.54 & 6.08 & 2.66 & 0.65 & 1.42 & 2.57 & 5.78 \\ \hline \hline \end{tabular}  
\({}^{1}\) Loss on ignition at 1000 \({}^{\circ}\)C.  
\end{table} 
Table 1: Elemental oxide composition of WBA powder. Figure 2: XRD pattern of WBA. The AA-WBA binders' preparation procedure began by mixing the NaOH and Na\({}_{2}\)SiO\({}_{3}\) (ratio of 1:4 by weight). This ratio was selected because a higher proportion of NaOH increases the porosity and reduces the mechanical performance of the binders [33]. Then, the WBA and the alkali-activator solution were mixed (liquid-to-solid ratio of 1:1 by weight) and mechanically stirred in a plastic beaker for 5 min. Fresh AA-WBA binders were poured into 25 mm cubic molds and sealed in plastic bags for 3 days in a climate chamber (\(25\pm 1\)\({}^{\circ}\)C and relative humidity of 95% \(\pm\) 5%). After 3 days, the samples were unmolded and removed from the plastic sealed bag, and the AA-WBA specimens continued curing in the climate chamber under the same above-mentioned conditions. Nine cubic-shaped specimens were prepared for each formulation. The AA-WBA specimens' characterization was carried out after 28 curing days. The hydrolytic stability of the AA-WBA binders was evaluated by introducing a dried cubic specimen of each formulation in boiling water for 20 min [39]. Afterwards, the specimen remained at room temperature until reaching a constant weight in a desiccator with silica gel. Then, before and after the test, the sample was weighed to determine the mass loss and to verify the chemical stability and resistance to the dissolution of the AA-WBA binders. The integrity of AA-WBA was assessed by introducing a cubic specimen in deionized water (liquid-to-specimen ratio of 10.0 by weight) under stirring for 2 days. Conductivity (k) and pH were measured (after 1, 15, 30, 60, 120, 240, 600, 1440, 2160, and 2880 min) to evaluate pH variation and ion diffusion over time and the effect that may have on the formation of cementitious phases. The main reaction product of alkali activation of calcium-rich precursors such as WBA [41] is calcium silicate hydrate (C-(A)-S-H) gel [39; 45]. C-(A)-S-H gel coexists in the AAC's microstructures along with the N-A-S-H gel [46]. It has even been reported that a mixture of both gels improves the durability of AAC's as compared to the single N-A-S-H gel [47]. However, when both formed gels coexist, it is difficult to conduct a proper elucidation of C-(A)-S-H using classical characterization techniques such as X-ray diffraction (XRD) or Fourier transform infrared spectroscopy (FTIR). For this reason, selective dissolution characterization is gaining popularity in order to eliminate any ambiguity between C-(A)-S-H and N-A-S-H gels [46]. AA-WBA binders were subjected to the salicylic acid/methanol (SAM) extraction [43] and HCl extraction [44] to determine C-(A)-S-H and N-A-S-H phases' content.