## 3 Analysis and Discussion of Test Results
### Basic Form Determination  
According to the previous relationship curve between the initial capillary water absorption of recycled concrete and the number of freeze-thaw cycles and the test data, by using Origin for fitting in various forms, the initial capillary water absorption and the num  
Figure 8: Capillary water absorption rates at the later stage of the freeze–thawing cycle for different media. (**a**) Freshwater freeze–thaw cycle; (**b**) sulfate freeze–thaw cycle; (**c**) chlorine salt freeze–thaw cycle. ber of freeze-thaw cycles of the specimens were obtained to obey a quadratic polynomial distribution, so that the expression of the prediction model is  
\[\text{S}_{1}=\text{A}+\text{BN}+\text{CN}^{2}\]  
where \(\text{S}_{1}\) is the initial capillary water absorption of recycled concrete; A, B, and C are the influence factors of freeze-thaw cycles; N is the number of freeze-thaw cycles; and R\({}^{2}\) is the fitted regression coefficient. Tables 7-9 describes the detailed fitting parameters  
According to the data obtained, the regression analysis of the pre-capillary water absorption of different specimens at 0, 50, 100, and 200 freeze-thaw cycles was carried out, and the relationship between the coefficients of different freeze-thaw cycles and different numbers of freeze-thaw cycles was obtained. Tables 10-12 lists the detailed analysis and fitting. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Number** & **Predictive Models** & **R\({}^{2}\)** \\ \hline RAC & y = (1.410 \(\times\) 10\({}^{-4}\)) x\({}^{2}\) = 0.00312x + 4.469 & 0.999 \\ WRAC & y = (9.36 \(\times\) 10\({}^{-5}\)) x\({}^{2}\) = 0.00198x + 4.300 & 0.997 \\ GRAC & y = (8.94 \(\times\) 10\({}^{-5}\)) x\({}^{2}\) = 0.00355x + 4.260 & 0.999 \\ WGRAC & y = (6.04 \(\times\) 10\({}^{-5}\)) x\({}^{2}\) + (-3.64 \(\times\) 10\({}^{-4}\)) x + & 0.998 \\  & 3.910 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Freeze-thaw initial capillary water absorption prediction model for clear water medium. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Number** & **A** & **B** & **R\({}^{2}\)** \\ \hline RAC & \(1.41\times 10^{-4}\) & \(-\)0.00312 & 0.999 \\ WRAC & \(9.36\times 10^{-5}\) & \(-\)0.00198 & 0.997 \\ GRAC & \(8.94\times 10^{-5}\) & \(-\)0.00355 & 0.999 \\ WGRAC & \(6.04\times 10^{-5}\) & \(-\)3.6 \(\times\) 10\({}^{-4}\) & 0.998 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Fitting parameters of capillary water absorption in clear water before freezing and thawing. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Number** & **Predictive Models** & **R\({}^{2}\)** \\ \hline RAC & y = (1.166 \(\times\) 10\({}^{-4}\)) x\({}^{2}\) = 0.001019x + 4.460 & 0.994 \\ WRAC & y = (9.94 \(\times\) 10\({}^{-5}\)) x\({}^{2}\) + 0.00587x + 4.280 & 0.997 \\ GRAC & y = (9.262 \(\times\) 10\({}^{-5}\)) x\({}^{2}\) + 0.00282x + 4.252 & 0.999 \\ WGRAC & y = (6.097 \(\times\) 10\({}^{-5}\)) x\({}^{2}\) + 0.00409x + 3.937 & 0.996 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Freeze-thaw initial capillary water absorption prediction model for sulfate medium. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Number** & **A** & **B** & **R\({}^{2}\)** \\ \hline RAC & \(1.166\times 10^{-4}\) & 0.01019 & 0.994 \\ WRAC & \(9.94\times 10^{-5}\) & 0.00587 & 0.997 \\ GRAC & \(9.262\times 10^{-5}\) & 0.00282 & 0.999 \\ WGRAC & \(6.097\times 10^{-5}\) & 0.00409 & 0.996 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Fitting parameters of capillary water absorption in the pre-freeze–thaw period with sulfate. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Number** & **A** & **B** & **R\({}^{2}\)** \\ \hline RAC & \(7.942\times 10^{-5}\) & 0.02329 & 0.997 \\ WRAC & \(6.317\times 10^{-5}\) & 0.01867 & 0.997 \\ GRAC & \(6.991\times 10^{-5}\) & 0.01146 & 0.993 \\ WGRAC & \(5.2\times 10^{-6}\) & 0.01530 & 0.964 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Fitting parameters of capillary water absorption in the pre-freeze–thaw period with chloride salt.