# Preliminary Study of New Sustainable, Alkali-Activated
## 2 Materials and Methods  
The CSP sample was collected from the glass treatment plant Daniel Rosas, S.A., located in Barcelona (Spain). This plant manages 90,000 t per year of glass cullet, collected in curbside containers. The particle size distribution (Figure 1a) and the percentage composition (Figure 1b) in mass were determined after cleaning the sample with soap, to eliminate the remains of dirt and fermions produced during the deposit of CSP in the treatment plant. As can be observed in Figure 1a, the highest percentage (wt %) for CSP was the 8-16 mm particle size fraction, followed by the size fraction \(>\) 16 mm. On the other hand, Figure 1b shows glass as the main component in CSP. Moreover, to improve the reactivity for AAC synthesis, the CSP sample was crushed and milled, using a ball mill, until CSP particle sizes were below 80 \(\upmu\)m. The particle size distribution (PSD) of the CSP used as precursor raw material (i.e., after crushing and milling below 80 \(\upmu\)m) was determined by using a Beckman Coulter LSTM 13 320. Additionally, the CSP powder semi-quantitative elemental analysis was carried out by a Panalytical Philips PW 2400 sequential X-ray fluorescence (XRF) spectrophotometer equipped with the software UniQuant V5.0. In addition, X-ray diffraction (XRD) analysis was conducted to determine the crystalline phases of CSP and the different AAC formulations using a Bragg-Brentano Siemens D-500 powder diffractometer device with CuK\(\alpha\) radiation. Fourier transform infrared spectroscopy (FTIR) by using the attenuated total reflectance sampling technique (ATR) was performed to compare the CSP initial powder structure before the AAC composition, employing Spectrum Two equipment from Perkin Elmer supported by a Dynascan interferometer and OpticsGuard technology. FTIR equipment is optimized by a wavelength range between 4000 cm\({}^{-1}\) and 500 cm\({}^{-1}\), and its standard spectral resolution is 0.5 cm\({}^{-1}\). Different alkaline solutions were studied as activators to elucidate the effect of the activator concentration in the AAC synthesis. For this purpose, various concentrations of sodium hydroxide solutions (1 M, 4 M, and 8 M) were prepared by using sodium hydroxide pearls (Labkem) dissolved in deionized water. Sodium hydroxide concentrations were chosen by following the conclusions reported by [PERSON] et al. when NaOH is used for geopolymer mortars made of glass cullet [33]. The AAC specimens using CSP as precursor were formulated by mixing the CSP powder (below 80 \(\upmu\)m) with the NaOH solutions as an alkaline activator, according to the designed formulations shown in Table 1. The same amount of CSP (16 g) was used for each formulation, and different amounts of NaOH solutions (8.0 and 9.6 g) were added to the CSP powder to obtain the two liquid-to-solid (L/S) ratios under study: 0.5 and 0.6. L/S ratios were selected after preliminary tests for obtaining proper workability of the mixtures. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Reference**} & \multirow{2}{*}{**CSP (g)**} & \multicolumn{3}{c}{**NaOH Solution (g)**} & \multirow{2}{*}{**L/S (wt \%)**} \\ \cline{3-3} \cline{5-5}  & & **1 M** & & **4 M** & **8 M** \\ \hline
05L51M & 16 & 8.0 & & & 0.5 \\
05L54M & 16 & & 8.0 & & 0.5 \\
05L58M & 16 & & & 8.0 & 0.5 \\
06L51M & 16 & 9.6 & & & 0.6 \\
06L54M & 16 & & 9.6 & & 0.6 \\
06L58M & 16 & & & 9.6 & 0.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The AAC mixture composition. Figure 1: CSP (ceramic, stone, and porcelain) waste as raw material and as an alkali-activated cement (AAC) precursor: (a) Particle size distribution in mass percentage; (b) CSP composition (wt %). The mixing process between CSP powder and the alkaline solution consisted of slowly adding the CSP powder to the NaOH solution while mixing mechanically for 5 min, thus contributing to its activation. Later, the mixed paste was cast into plastic molds and vibrated for 5 s to compact the mixture.