## 3 Result Analysis
### Mercury Intrusion Porosimetry  
#### 3.3.1 Results of Mercury Intrusion Porosimetry  
The MIP was carried out on the samples with different geopolymer contents. The pores were divided into four categories according to the size of the pores [34]: harmless pores (<20 nm), less harmful pores (20-50 nm), harmful pores (50-200 nm) and more harmful pores (>200 nm). The experimental results are indicated in Table 12.  
As shown in the MIP results in Table 12, combined with Figure 11, with an increase in cycles, the porosity of the mixture without geopolymer, 20% geopolymer and 40% geopolymer showed an increasing trend. This shows a positive correlation between the number of freezing and thawing cycles and porosity. In addition, regardless of the number of cycles, the porosity of the mixture with 20% geopolymer is always lower than that of the mixture without geopolymer and the mixture with 40% geopolymer. From the perspective of macroscopic mechanical properties, the mechanical properties of the mixture reduce with increasing cycles. However, the UCS and ITS of the mixture with 20% geopolymer are better than those of the mixture without geopolymer and the mixture with 40% geopolymer. By observing the change in pore size distribution for the single geopolymer content mixture (taking 20% content as an example) in Figure 12, we find that the more cycles, the more the porosity of harmless pores in the four types of pores gradually decreases, while the number of harmful pores and more harmful pores gradually increases. This is consistent with the change trend of macroscopic mechanical properties; that is, with more cycles, the mechanical properties of the mixture with 20% geopolymer decrease gradually. Figure 10: SEM images of different cycles of mixture with 3000-times magnification and 20% geopolymer content: (**a**) 5 cycles, (**b**) 10 cycles, (**c**) 20 cycles. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Freeze–Thaw** & \multirow{2}{*}{\begin{tabular}{c} **Geopolymer** \\ **(Number of** \\ **Cycles)** \\ \end{tabular} } & **Hemless** & \multirow{2}{*}{\
\begin{tabular}{c} **Less** \\ **Harmful** \\ **Pores (\%)** \\ \end{tabular} } & **Harmful** & \multirow{2}{*}{
\begin{tabular}{c} **More** \\ **Pores (\%)** \\ \end{tabular} } & **Total** \\  & & & & & & **Harmful** \\  & & & & & **Pores (\%)** & \\ \hline
1 & & 0 & 3.93 & 1.80 & 1.46 & 4.05 & 11.24 \\
2 & 0 & 20 & 4.17 & 1.50 & 1.28 & 3.74 & 10.68 \\
3 & & 40 & 3.32 & 1.95 & 1.83 & 4.35 & 11.45 \\
4 & & 0 & 4.38 & 1.99 & 1.99 & 4.91 & 13.27 \\
5 & 5 & 20 & 4.09 & 2.04 & 1.80 & 4.09 & 12.02 \\
6 & & 40 & 3.73 & 2.29 & 2.72 & 5.59 & 14.34 \\
7 & & 0 & 4.00 & 2.72 & 2.88 & 6.40 & 16.00 \\
8 & 10 & 20 & 3.99 & 2.57 & 2.28 & 5.27 & 14.27 \\
9 & & 40 & 3.69 & 2.64 & 3.69 & 7.56 & 17.59 \\
10 & & 0 & 3.99 & 2.26 & 3.30 & 7.64 & 17.36 \\
11 & 20 & 20 & 4.21 & 2.27 & 2.91 & 7.32 & 16.18 \\
12 & & 40 & 3.90 & 2.15 & 4.10 & 9.36 & 19.50 \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Test results of MIP. 3.2. Grey Relation Analysis of Mixture Performance Index and MIP Results under Freeze-Thaw Cycle Conditions  
According to the results of freezing and thawing cycle tests and MIP, we can find that when the geopolymer content is 20%, the UCS and ITS of the mixture are always higher than those of the mixture without geopolymer and 40% geopolymer content, and less strength is wasted than that of the mixture without geopolymer and 40% geopolymer content. The comprehensive performance is the best among the three dosages; in addition, combined with Tables 11 and 12, it is found that with an increase in cycles, under the same dosage, pores with a diameter of 50 nm or more and total porosity gradually increase, and the UCS and ITS of the mixture gradually decrease. Based on this, it is speculated that there is a certain relationship between the mechanical properties of the mixture and the distribution of harmful pores, more harmful pores and total porosity.