## 3 Results and Discussion
### Simulating Agro-Based Materials Production  
#### 3.5.1 Agro-Based Concrete Simulation--Alkaline Extraction  
* pH monitoring during alkaline extraction  
The pH values measured at 0, 30, and 60 min for each condition in the \"agro-based concrete\" simulation are summarized in Table 6. The conditions include milli-Q water at room temperature (RT) and 50 \({}^{\circ}\)C, as well as alkaline extractions using NaOH or Ca(OH)\({}_{2}\) at a pH of 12.5. These data allow us to evaluate the effects of temperature and alkaline conditions on pH changes. For the extraction at room temperature (RT), no significant pH differences were observed between HS1 and HS2, nor between the measurements taken at 0 and 60 min. Initially, the pH for both types of hemp shiv was 5.60 for HS1 and 5.66 for HS2, and after 60 min, the pH slightly shifted to 5.65 for HS1 and 5.64 for HS2. However, when the temperature was increased to 50 \({}^{\circ}\)C, the pH behavior differed between the two samples. For HS1, the pH decreased from 5.86 to 5.64, indicating a drop of about 0.22 pH units. This suggests that HS1 released acidic compounds, potentially acidic sugars such as galacturonic or glucuronic acids, derived from the breakdown of pectins. In contrast, the pH of HS2 unexpectedly increased from 5.81 to 6.27, a rise of almost 0.5 pH units. This suggests the release of basic and/or neutral compounds, indicating a different chemical response to elevated temperatures compared to HS1. \begin{table}
\begin{tabular}{c c c} \hline  & **Apparent Density** & **Skeletal Density** \\ \hline HS1 & 135.1 \(\pm\) 4.9 & 1338.4 \(\pm\) 1.1 \\ \hline HS2 & 103.0 \(\pm\) 5.5 & 1331.0 \(\pm\) 3.5 \\ \hline \end{tabular}
\end{table} 
Table 5: Apparent and skeletal densities measured for HS1 and HS2. For NaOH solution at room temperature, the pH of HS1 decreases from 12.50 to 12.08, representing a decrease of 0.42 pH units. HS2 shows a smaller decrease from 12.47 to 12.34, a change of 0.13 pH units. When the temperature is raised to 50 \({}^{\circ}\)C, HS1's pH drops by 1.18 pH units to 11.32. HS2 experiences a decrease of 0.8 pH units to 11.67. The combined effect of NaOH and elevated temperature results in a greater pH reduction compared to room temperature conditions, with HS1 showing a decrease of 1.18 pH units and HS2 a decrease of 0.80 pH units. This demonstrates that the increase in both pH and temperature results in a more significant reduction in pH. For Ca(OH)\({}_{2}\) at room temperature, HS1's pH decreases from 12.50 to 12.23, a change of 0.27 pH units. HS2's pH drops from 12.48 to 12.20, a decrease of 0.28 pH units. At 50 \({}^{\circ}\)C, HS1's pH falls to 11.30, reflecting a decrease of 1.20 pH units, while HS2's pH decreases to 11.13, a reduction of 1.35 pH units. HS1 seems more sensitive to the NaOH base, while HS2 is more sensitive to Ca(OH)\({}_{2}\). The observed differences in reaction kinetics between HS1 and HS2, depending on the alkaline base and temperature, can be attributed to the distinct chemical compositions of the hemp shiw samples (Tables 3 and 4). At pH 12.50, the main components extracted are hemicellulose, lignin, polyphenols, and pectins. These compounds interact with Ca\({}^{2+}\) or Na\({}^{+}\) ions through ionic bonding, either in their carboxylate forms for saccharides or through non-bonding electron pairs on oxygen atoms [32]. Given that HS2 contains more lignin and polyphenols compared to HS1, while HS1 has a higher sugar content, it is likely that HS1 releases more sugars that interact with Na\({}^{+}\) under basic conditions, whereas HS2 releases more polyphenols that interact with Ca\({}^{2+}\). Competitive interactions between the released compounds and the base, due to differences in chemical composition, may also influence the pH changes observed. Homogalacturonan chains in pectins can exist in either a methyl-esterified or demethylesterified form.