## 2 Experimental Program  
### Materials and Methods  
The mean particle sizes of WGP derived from waste glass vessels were 75 \(\upmu\)m and 300 \(\upmu\)m. Before being crushed and ground, the vessels were cleaned to eliminate labels and taps and then air-dried. Then, the milled WGP was properly reserved in a sealed and dry container. Figure 1 shows the 75 \(\upmu\)m and 300 \(\upmu\)m WGP, and Table 1 presents the chemical ingredients. The high silicon dioxide content (approximately 74%) demonstrates the excellent potential of WGP as pozzolans [37]. The ordinary Portland cement (with a strength grade of 42.5) was utilised as an essential binder composition, whose physical and chemical indexes are presented in Table 2. Natural sand was used as the filler with over 96% silicon dioxide, and ASTM C778 [38] was used for its gradation before use. Figure 1: The features of WGP of different granularity: **(a)** 75 \(\upmu\)m; **(b)** 300 \(\upmu\)m.  
To investigate the activation effects, five variables were considered: the particle size and substitute proportion of WGP, the category and content of the chemical activators, and the curing times. These five variables were set as the features for the ML modelling. Natural sand was replaced with WGP (75 \(\upmu\)m and 300 \(\upmu\)m) on three levels (10 wt%, 20 wt%, and 30 wt%). The chemical additive comprises a salt activator (sodium sulphate) and alkaline activators (calcium hydroxide and sodium hydroxide). Additionally, the water-to-cement (W/C) and aggregate-to-cement ratios (A/C) were maintained at 0.47 and 2.25, respectively. The following is the detailed activation methodology:  
* Mechanical activation: By employing a ball mill, a glass cullet was ground into WGP with two particle sizes: 300 \(\upmu\)m and 75 \(\upmu\)m. Compared to coarse WGP (300 \(\upmu\)m), the finer WGP was supposed to acquire better pozzolanic characteristics. * Chemical activation: Sodium hydroxide, calcium hydroxide, and sodium sulphate (anhydrous) were the three agents used to activate WGP and the WGP-cement system. They are all analytically pure (AR) and commercially available. The alkaline activator is composed of 50 wt% sodium hydroxide and 50 wt% calcium hydroxide, and sodium sulphate served as a salt activator. Both activators were jointly applied at 2 wt%, 4 wt%, and 6 wt% of cement. Before their application, sodium sulphate and sodium hydroxide were dissolved in water, while calcium hydroxide was directly mixed with WGP and sand. The mixing time was enough for the thorough dispersion of raw materials as per ASTM C305 [39]. * Combined activation: The mechanical-chemical activation integrated the abovementioned mechanical and chemical approaches, where the 300 \(\upmu\)m WG was ground to 75 \(\upmu\)m WGP, and the chemical activators were utilised in the meantime. In total, 60 mixes with one control group are summarised in Table 3, where the WG, sodium sulphate, and alkali activators are expressed as G, S, and H, respectively. The particle sizes of WGP are represented as the numbers 75 and 300 without the unit. The numbers 10, 20, and 30 represent the replacement ratios of WGP, i.e., 10%, 20%, and 30%, respectively. The numbers 2, 4, 6 represent the chemical activators' ratios of 2%, 4%, and 6%, respectively. \begin{table}
\begin{tabular}{c c} \hline \hline
**Composition** & **Waste Glass Powder** \\ \hline SiO\({}_{2}\) & 74.02\% \\ Al\({}_{2}\)O\({}_{3}\) & 1.40\% \\ Fe\({}_{2}\)O\({}_{3}\) & 0.19\% \\ CaO & 11.25\% \\ MgO & 3.34\% \\ SO\({}_{3}\) & 0.33\% \\ Na\({}_{2}\)O & 9.03\% \\ K\({}_{2}\)O & 0.29\% \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical ingredients of WGP.