## 2 Materials and Methods
### Sample Preparation and Test Methods  
A cement paste mixer was used. First, cement was put into the mixing pot, and then superplasticizer was mixed into water and stirred uniformly. Finally, the water and superplasticizer were poured into the mixing pot. When cement pastes were stirred, they were stirred slowly for 2 min, and then fast for 2 min. The expansion degree, determined using a mortar expansion degree determinator, was 300 mm. The specimens were cast in moulds and compacted on a vibration table. To control the leakage of cement pastes during the mixing, moulding, and compacting processes, the sealant was brushed at the mould bottom. Three specimens of dimensions 40 mm \(\times\) 40 mm \(\times\) 160 mm were prepared for each group. The moulded specimens were placed at normal temperature for 1 d, after which the moulds were removed. The specimens were then placed in a standard curing room (20 \(\pm\) 2 \({}^{\circ}\)C and RH \(\geq\) 95%) for up to 28 d, and the completion of curing was selected as the starting point of the further hydration test. The specimens were placed under different temperature and humidity conditions to perform a further hydration experiment. The compressive strength, flexural strength, and expansion strain of the specimens were measured until the specified testing time. Different humidity environments were realised in the following ways: (1) Sealing state: the surface moisture of the specimen was dried, and then the specimen was sealed using a \begin{table}
\begin{tabular}{c c c c c} \hline
**Item** & **C\({}_{3}\)S** & **C\({}_{2}\)S** & **C\({}_{3}\)A** & **C\({}_{4}\)AF** \\ \hline mass fraction/\% & 56.23 & 22.08 & 6.40 & 10.28 \\ \hline \end{tabular}
\end{table} 
Table 1: Mineral composition of cement. \begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Item** & **SiO\({}_{2}\)** & **Al\({}_{2}\)O\({}_{3}\)** & **Fe\({}_{2}\)O\({}_{3}\)** & **CaO** & **MgO** & **SO\({}_{3}\)** & **Na\({}_{2}\)O\({}_{\text{eq}}\)** & _f-CaO_ \\ \hline mass fraction/\% & 22.19 & 4.48 & 3.23 & 63.10 & 2.41 & 2.57 & 0.53 & 0.88 \\ \hline \end{tabular}
\end{table} 
Table 2: Chemical composition of cement. \begin{table}
\begin{tabular}{c c c c c} \hline
**Cement** & **Superplasticizer** & **Water** & **Water–Binder Ratio** & \
\begin{tabular}{c} **Compressive Strength at** \\ **the Age of 28 d/MPa** \\ \end{tabular} &
\begin{tabular}{c} **Flexural Strength at the** \\ **Age of 28 d/MPa** \\ \end{tabular} \\ \hline
1.00 & 0.01 & 0.194 & 0.20 & 91.9 & 8.1 \\ \hline \end{tabular}
\end{table} 
Table 3: Mixing ratio. plastic film and finally placed in an environment of 20 \(\pm\) 2 \({}^{\circ}\)C; (2) RH50% \(\pm\) 5%: the surface moisture of the specimen was dried, and the specimen was placed in an environment of 20 \(\pm\) 2 \({}^{\circ}\)C and RH of 50 \(\pm\) 5%; (3) RH \(\geq\) 95%: the specimen was placed in a standard curing room. Different temperature environments were realised through water soaking at 20 \({}^{\circ}\)C, 40 \({}^{\circ}\)C, and 60 \({}^{\circ}\)C.  
The ignition loss method was used to determine the chemically combined water content in three samples from each group. The crushed samples were ground into powder through a sieve with a diameter of 80 \(\mu\)m and the powder samples were placed in a dryer. During the test, each sample weighed about 10 g. The powder samples were put into a high-temperature furnace and heated to 105 \({}^{\circ}\)C for more than 3 h, then they were weighed after the samples were cooled. After weighing, they were placed in a high-temperature furnace again and heated to 950 \({}^{\circ}\)C for more than 3 h, then the samples were weighed again.