## 3 Experimental Analysis of Steam Curing and Orthogonal Matching Ratio
### Steam Curing Test Analysis
The test plan and results are shown in Table 10.  
As shown in Table 10, under heating rates of 15 \({}^{\circ}\)C/h, 20 \({}^{\circ}\)C/h, and 25 \({}^{\circ}\)C/h, the 3-day compressive strength of the specimens increased by 26.33%, 37.87%, and 32.71%, respectively, compared to standard curing; the 7-day strength rose by 18.45%, 28.09%, and 23.74%; the 14-day strength increased by 7.08%, 14.19%, and 8.96%; and the 28-day strength improved by 3.29%, 10.98%, and 7.07%. Among these, a heating rate of 20 \({}^{\circ}\)C/h yielded the highest compressive strength at 3, 7, 14, and 28 days compared to 15 \({}^{\circ}\)C/h and 25 \({}^{\circ}\)C/h. Compared to 15 \({}^{\circ}\)C/h, compressive strength at 20 \({}^{\circ}\)C/h increased by 8.85%, 8.13%, 6.64%, and 7.45% at 3, 7, 14, and 28 days, respectively; compared to 25 \({}^{\circ}\)C/h, the increases were 3.88%, 3.51%, 4.81%, and 3.65%. These results indicate that increasing the heating rate from 15 \({}^{\circ}\)C/h to 20 \({}^{\circ}\)C/h enhances compressive strength across all curing ages; however, further increasing it to 25 \({}^{\circ}\)C/h leads to a reduction in strength. This suggests that a moderate increase in heating rate promotes cement hydration and early strength development, whereas an excessively high rate may induce expansion and cracking of the cementitious matrix, thereby compromising structural integrity. Therefore, considering compressive strength development across all curing ages, the optimal heating rate in this test segment is determined to be 20 \({}^{\circ}\)C/h. (4) Constant temperature is a key factor affecting the strength of fly ash cement mortar. The test plan and results are shown in Table 11. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Group**} & **Resting** & **Heating** & **Constant** & **Constant** & \multicolumn{3}{c}{**Compressive Strength**} \\  & **Time (h)** & **Rate (\({}^{\circ}\)C/h)** & **Temperature (\({}^{\circ}\)C)** & **Temperature Time (h)** & **3 d** & **7 d** & **14 d** & **28 d** \\ \hline SS-15 & 24 & 15 & 50 & 24 & 21.14 & 27.54 & 30.25 & 31.41 \\ SS-20 & 24 & 20 & 50 & 24 & 23.01 & 29.78 & 32.26 & 33.75 \\ SS-25 & 24 & 25 & 50 & 24 & 22.15 & 28.77 & 30.78 & 32.56 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Summary table of test plans and test results. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Number**} & **Resting** & **Heating** & **Constant** & \multicolumn{3}{c}{**Constant**} & \multicolumn{3}{c}{**Compressive Strength**} \\  & **Time (h)** & **Rate (\({}^{\circ}\)C/h)** & **Temperature (\({}^{\circ}\)C)** & **Temperature Time (h)** & **3 d** & **7 d** & **14 d** & **28 d** \\ \hline JY-06 & 6 & 20 & 50 & 24 & 18.12 & 24.14 & 27.98 & 30.25 \\ JY-12 & 12 & 20 & 50 & 24 & 19.35 & 26.13 & 29.36 & 31.12 \\ JY-18 & 18 & 20 & 50 & 24 & 21.26 & 27.56 & 31.97 & 33.23 \\ JY-24 & 24 & 20 & 50 & 24 & 23.01 & 29.78 & 32.26 & 33.75 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Summary table of test plans and test results. As shown in Table 11, under constant temperatures of 40 \({}^{\circ}\)C, 50 \({}^{\circ}\)C, and 60 \({}^{\circ}\)C, the 3-day compressive strength of the specimens increased by 18.51%, 37.87%, and 40.30%, respectively, compared to standard curing; at 7 days, strength increased by 17.16%, 28.09%, and 31.44%; at 14 days, by 5.03%, 14.19%, and 12.50%; and at 28 days, by 3.53%, 19.47%, and 13.70%. It is evident that at a curing temperature of 60 \({}^{\circ}\)C, the compressive strength at 3 and 7 days exceeded those at 40 \({}^{\circ}\)C and 50 \({}^{\circ}\)C, indicating enhanced early strength development. However, at 14 and 28 days, the strength was lower than that observed in the 50 \({}^{\circ}\)C group, indicating a noticeable decline.