## 3 Results  
### Fundamental Physical Properties  
As shown in Figure 5, the apparent color of Huizhou limestone under the effect of thermal shock is mainly affected by the peak temperature of heating. The surface of the specimen heated at 300 \({}^{\circ}\)C or less is grayish white, with local greenish gray and rusty red mineral inclusions. When heated to 400 \({}^{\circ}\)C-500 \({}^{\circ}\)C, the surface of the specimen changes to earthy yellow and the range of rusty red increases. In contrast to the conclusions reached by other studies [12] (significant changes in limestone surface color after high temperature action at 700 \({}^{\circ}\)C), the apparent color of the specimens significantly changed at 600 \({}^{\circ}\)C under thermal shock; i.e., an overall shift to white. It shows that the thermal shock effect is stronger than the high temperature effect on limestone when the heating temperature is the same. Figure 5: Specim apparent color change diagram (the fissures were marked in red). The tests showed that the mass of limestone specimens decreased and the volume increased under the effect of thermal shock. The decrease in mass of limestone under thermal shock is due to evaporation of internal water, the decomposition of some minerals, and a small amount of flaking of rock chips. The expansion of mineral grains and the generation of a large number of fractures under thermal shock combined to cause the increase in limestone volume. Mass loss results of limestone specimens are presented in Figure 6A. The mass loss rate of limestone increases with the increase in heating temperature after thermal shock. Taking cooling in water at 20 \({}^{\circ}\)C as an example: the mass loss rate of the specimen below 300 \({}^{\circ}\)C remains unchanged at about 0.092%. A slow increase in mass loss rate to 0.183% from 300 \({}^{\circ}\)C to 500 \({}^{\circ}\)C, with an increase of 101% compared to 300 \({}^{\circ}\)C. When the temperature increases to 600 \({}^{\circ}\)C, the mass loss rate of limestone rapidly increases to 0.882%, which is 4.82 times that of 500 \({}^{\circ}\)C and, even more, 9.48 times that of 100 \({}^{\circ}\)C. The main reason for the change in the mass of the specimen within 500 \({}^{\circ}\)C is the evaporation and release of the water inside the rock. The mass loss of limestone from 20 \({}^{\circ}\)C to 300 \({}^{\circ}\)C is mainly dominated by the evaporation of free water. Because the water content of the specimen is small, the mass remains essentially unchanged at this stage. Within the temperature range of 300 \({}^{\circ}\)C-500 \({}^{\circ}\)C, the combined water inside the limestone gradually evaporates and the mass of the specimen slowly decreases. Above 500 \({}^{\circ}\)C, the internal mineral components of limestone gradually decompose. Moreover, the thermal shock rupture produced by the specimen at this temperature is significant at either cooling temperature, and a small number of mineral particles flake off from the specimen. Therefore, the mass of limestone rapidly decreases at this stage, and the mass loss rate increases significantly. Due to the anisotropy of limestone and the different thermal expansion coefficients of different mineral particles, the volume of the specimen nonlinearly increases, so the data distribution of the volume expansion rate of high-temperature limestone after the thermal shock is more discrete. As shown in Figure 6B, the variation of limestone volume with heating temperature is similar after thermal shock in water at different temperatures. The volume of limestone increases with increasing heating temperature (general trend), but there are differences in the inflection point temperature of volume abrupt change (the part marked by circles in the figure). The volume abrupt change temperature is 300 \({}^{\circ}\)C for limestone cooled in 20 \({}^{\circ}\)C water, and 200 \({}^{\circ}\)C for limestone cooled in 60 \({}^{\circ}\)C and 100 \({}^{\circ}\)C water.