## Materials and Methods
### Methods  
The experiment used an integrated setup that included loading equipment, a heating apparatus, and a control and data acquisition system, enabling three-point bending tests under varying real-time temperature conditions. Figure 2 depicts the loading system comprising a reaction frame, fixture base, pressure bar, and fixture, with a maximum axial pressure capacity of 300 kN. The heating equipment consists of a temperature chamber and a heat exchange machine, encompassing a temperature range from \(-\)70 to 400 \({}^{\circ}\)C with an accuracy of \(\pm\)0.1 \({}^{\circ}\)C, as illustrated in Figure 3. The temperature control screen on the heat exchange machine's side facilitates the adjustment of the temperature rise rate and the target temperature. The control and data acquisition system includes a force-displacement sensor and a terminal computer capable of collecting force-displacement data at 30 Hz. As a reference value in CTB tests, the peak load P\({}_{\text{maxT}}\) from the MTB test conducted at a loading rate of 0.1 mm/min was recorded and is presented in Table 2, following the approach presented by [PERSON] et al. [41]. The SCB samples were categorized into 16 distinct groups. To maintain the accuracy and reliability of the test, each working condition was assessed with three separate samples. During the preliminary tests, it was observed that when the upper load limit exceeded 90%, the samples frequently failed before reaching the upper load limit. Conversely, when the upper load limit was set below 75%, it proved challenging for the samples to reach the point of failure. Therefore, the CTB tests were conducted with four different upper load limits (75%, 80%, 85%, and 90% of P\({}_{\text{maxT}}\)) and at four different temperature levels (25 \({}^{\circ}\)C, 200 \({}^{\circ}\)C, 300 \({}^{\circ}\)C, and 400 \({}^{\circ}\)C), respectively. In the initial step, the granite sample was positioned at the center of the three-point bending fixture. Next, the sample was centered within the temperature chamber by pushing the chamber into position. Subsequently, the temperature chamber was securely fixed, and the chamber door was closed. Concurrently, insulation cotton was introduced into the gap between the connecting \begin{table}
\begin{tabular}{c c c c c} \hline
**R/(mm)** & **B/(mm)** & **t/(mm)** & **a/(mm)** & **S/(mm)** \\ \hline
38 \(\pm\) 0.3 & 30 \(\pm\) 0.2 & 1 & 19.5 \(\pm\) 0.3 & 60.8 \\ \hline \end{tabular}
\end{table} 
Table 1: Basic geometrical parameters of granite samples and the three-point bending fixture, where R is the radius, B is the thickness, t is the thickness of the pre-crack, a is the length of the pre-crack, and S is the distance between two supporting rollers. Figure 2: Configuration of the loading equipment: (**a**) testing machine and (**b**) three-point bending fixture with (1) compression roller, (2) SCB sample, (3) supporting roller, and (4) pedestal. rod and the temperature chamber to minimize heat loss and maintain a stable temperature environment. Throughout the heating process, temperature gradually increased to the specified levels (25 \({}^{\circ}\)C, 200 \({}^{\circ}\)C, 300 \({}^{\circ}\)C, and 400 \({}^{\circ}\)C) at a predefined rate of 10 \({}^{\circ}\)C per minute. This heating rate was adopted to minimize the impact of thermal gradients within the sample, following the approach outlined by [PERSON] et al. [42]. Subsequently, the temperature chamber was maintained at the target temperature for 2 h to ensure uniform heating of the samples, in line with the methodology recommended by [PERSON] et al. [43; 44]. After the temperature stabilization phase, the sample was subjected to CTB tests under the same loading and heating conditions as the in MTB test. This process continued until either the sample reached failure or the predefined limit of 200 loading cycles. In the CTB tests, it is essential to note that the lower load limit, represented by the lowest load value in each cycle, was consistently set at 150 N for all the samples.