## 3 Results and Discussion
### Analysis on the Correlation of SPRG Viscosity and Adhesion Strength on Wet Surface  
To analyze the correlation of SPRG viscosity and changes to the adhesion strength on varying humidity ratios of substrate surface, linear regression analysis based on the specimens of different viscosity modifier content ratio (D1-D8) and the respective adhesive strength throughout different humidity ratios was conducted.  
Based on the linear regression analysis, the coefficient of determination (denoted as \(R^{2}\)) was derived to provide the basis of correlation. The correlation coefficient is typically calculated as the square of the correlation coefficient (\(r\)) between two variables, measuring the strength and direction of the linear relationship between the two variables, while the coefficient of determination indicates the proportion of variance in the dependent variable that is explained by the independent variable(s) [18; 19]. The coefficient of determination was calculated using the following Equation (2):  
\[R^{2}=1-\frac{SS_{res}}{SS_{tot}} \tag{2}\]  
where  
\(R^{2}=\) Coefficient of determination  
\(SS_{tot}=\) Total sum of squares  
\(SS_{res}=\) Residual sum of squares.  
Based on the linear regression, an appropriate viscosity range corresponding to the applicable range of surface humidity ratio condition is proposed at the end.  
Correlation Analysis and Consideration of Adhesion Performance according to Humidity Ratio of Substrate Surface  
Regression analysis was conducted based on Table 5, individually for the specimen types, which evaluated the adhesion performance of the adhesive gel waterproofing material according to the substrate surface humidity ratio and viscosity, to analyze the correlation between adhesion performance and substrate surface humidity ratio. Regression analysis was carried out using the SPSS regression analysis program, and the analysis results are considered relevant when the determination coefficient (\(R^{2}\)) is 0.8 or higher, indicating a  
Figure 5: Visual representation of the pull-off test results from Table 5.  
high explanatory power. Figure 6 below lists the regression analysis results of specimens D1 to D8:  
The regression analysis results of the adhesion performance, according to the substrate surface humidity ratio with a viscosity modifier content of 3%(D1) to 10%(D8) shown in Figure 6, were used to derive the linear regression equation and the coefficient of determination. The results are listed in Table 6 below.  
Figure 6: Linear regression analysis of adhesive strength vs different substrate surface relative humidity ratio of different specimens: (**a**) D1 results; (**b**) D2 results; (**c**) D3 results; (**d**) D4 results; (**e**) D5 results; (**f**) D6 results; (**g**) D7 results; and (**h**) D8 results.  
The coefficient of determination explaining the correlation between the substrate surface humidity ratio and the adhesion performance of SPRGs with varying viscosity were all above the required value of 0.8, ranging from the lowest 0.8964 (D6) to the highest of 0.9895 (D4). The results have shown that the regression equation has high reliability due to high ranges of coefficient of determination, and it can be concluded that there is a correlation between the adhesion performance changes of the adhesive gel waterproofing material according to the substrate surface humidity ratio. Based on these factors, a reliable methodology for recommending SPRG viscosity modifier content (limited to the SPRG material type tested in this study) is provided in the following section.