## 3 Results and Discussion
### Coefficient of Determination Analysis of Strength with TGA and Color Difference  
The strength, thermogravimetry, and color-difference results of HSCs were subjected to simple linear regression analysis to find correlations based on the age of the HSCs. For each model, a linear function formula was derived using a trend line between the strength and TGA (m) as well as color-difference analysis factors at each age. Here, the trend line for each relationship is associated with a coefficient of determination, R\({}^{2}\). Figure 9a-d shows the linear functions that represent the correlations between the measurement results and the corresponding R\({}^{2}\) values. Data points with R\({}^{2}\) close to 1 are indicated in blue, whereas those with R\({}^{2}\) close to 0 are indicated in orange. To show the color correlation between the existing pigments, techniques such as Huffman coding were used, and simultaneously, an image color-extraction algorithm using color correlation is being developed [52]. Most existing studies have verified only the relationship between the color-correlation factors, and several studies have been conducted to extract colors via verification analysis. To date, the characteristic factors of concrete and cement composites based on color correlation have not been reviewed in the construction field. For each specimen aged 3 days, the R\({}^{2}\) between strength and other factors was confirmed, and the strength-TGA (\(\Delta\)m) correlation coefficient of the green series showed the highest value. However, the initial intensity of the green series was rather low, and G5 recorded the highest value of m at the corresponding age. In the case of the red series, the initial strength and \(\Delta\)m were lower than those of P and showed a similar trend even when the mixing rate was increased. If the initial intensity was low, the correlation between \(\Delta\)m and the color factors was judged to be low. Figure 8: _Cont._  
Figure 8: CIELAB analysis of HSCCs. The average coordinates of color measurement from (1) to (9) are presented in Figure 7. (**a**) Average value of the color-measurement section of specimen P at each age, (**b**) average value of the color-measurement section of specimen R5 at each age, (**c**) average value of the color-measurement section of specimen R10 at each age, (**d**) average value of the color-measurement section of specimen G5 at each age, and (**e**) average value of the color-measurement section of specimen G10 at each age. Figure 9: Correlation analysis matrices of HSCs at different ages, showing the R\({}^{2}\) of specific factors measured at (**a**) 3 days, (**b**) 7 days, (**c**) 28 days, and (**d**) all ages (3–28 days). However, the 7-day-old specimen showed a different trend from the 3-day-old specimen. The strength of all specimens increased after the age of 3 days. However, the total \(\Delta\)m in G5 decreased at the age of 7 days. When correlating the strengths of the 7-day-old specimens and \(\Delta\)m, R\({}^{2}\) was found to increase when \(\Delta\)m decreased and to decrease when \(\Delta\)m increased. The change in the total amount of hydrate in the specimen at the relevant age decreases as the strength increases. According to the previous analyses, as the strength increases, hydrates are generated, thereby changing the total amount of hydrates. However, in the correlation analysis, the reduction in the amount of hydrate at the time of strength expression was higher in R\({}^{2}\). Therefore, this subject requires further analysis. R5 at 7 days of age was considered to have a high correlation between the intensity and color factors. It was judged that the R5 specimen shows color development relative to the initial color when the intensity is expressed. The 28-day-old specimens showed higher correlations between the strength and analysis factors than the unaged specimens. Except for the a* of specimen P, TGA (\(\Delta\)m) of R10, and a* of G10, R\({}^{2}\) was calculated to be 0.5 or higher.