High Temperature Damage Research Articles

Experimental Study on Fire Resistance of Geopolymer High-Performance Concrete Prefabricated Stairs

Geopolymer-based high-performance concrete (GHPC) stairs have been proposed as an alternative solution that fulfills both lightweight and load-bearing requirements for prefabricated stairs. Nevertheless, the fire resistance properties of GHPC stairs remain uncertain. Therefore, this study first conducts high-temperature experimental research on GHPC test blocks. The experimental results demonstrated that the GHPC test blocks exhibited no signs of bursting at elevated temperatures and displayed less degradation in the compressive strength compared to that of ordinary concrete. Subsequently, GHPC-Z stair specimens with ribbed and unribbed configurations were fabricated to conduct a fire resistance test at elevated temperatures, followed by a comparative analysis of the resulting damage. The test results indicate that both types of GHPC stairs demonstrate exceptional performance without exhibiting bursting or noticeable cracks or structural spalling marks on their main bodies, despite experiencing vertical deformation. Furthermore, based on these findings, finite element models were established to simulate the fire-induced damage in GHPC and ordinary concrete stairs without ribbed folding plates. The simulation results illustrate that GHPC stairs possess commendable fire resistance capabilities along with an ability to effectively recover from high-temperature damage.

Experimental Test and Analytical Calculation on Residual Strength of Prestressed Concrete T-Beams After Fire

High temperatures during a fire can lead to the evaporation of moisture and the degradation of hydration products within concrete, consequently compromising its mechanical properties. This paper thoroughly investigates the effect of fire-induced high temperatures on the residual load-bearing capacity of concrete structures, with a focus on prestressed concrete T-beams. By conducting constant temperature tests and residual load-bearing capacity tests, complemented by finite element modeling, this study examines the degradation of mechanical properties in prestressed concrete T-beams due to fire exposure and its impact on post-fire residual load-bearing capacity. Additionally, an equivalent concrete compressive strength method was employed to propose a calculation method for concrete material degradation under high temperatures and a corresponding concrete strength reduction factor. Simplified calculations were also performed for the high-temperature damage to reinforcement and prestressed tendons, leading to the derivation of a simplified formula for the residual load-bearing capacity of post-fire prestressed concrete T-beams. The results indicate that in prestressed concrete T-beams exposed to fire, an increase in holding time results in more severe damage modes, accelerated crack propagation, and wider crack widths during bending failure. Under the same load, a longer holding time corresponds to a more pronounced reduction in deflection. At holding times of 60 min, 120 min, and 180 min, the prestress losses were 48.17%, 85.16%, and 93.26%, respectively. The cracking load decreased by 15%, 27%, and 42%, while the residual load-bearing capacity decreased by 11%, 21%, and 28%. Comparison with experimental data demonstrates that both the finite element model and the simplified calculation formula exhibit high accuracy, offering a reliable reference for the performance evaluation of post-fire prestressed concrete T-beams.

A simplified procedure for evaluation of damage-depth in concrete exposed to high temperature using the impact-echo method

Concrete is widely recognized as a material capable of withstanding the intrusion of high temperatures during fires. However, under different high-temperature conditions, concrete can still experience strength reduction, cracking, or spalling, which can significantly impact the safety and durability of concrete structures. Conventionally, the wave refraction technique was used to detect the depth of this damage layer. However, the wave refraction technique is a time-consuming point-by-point detection method. In order to increase detection efficiency, this paper proposes a simplified method based on a single-point test. Numerical analysis of the thermal conduction of a concrete slab exposed to elevated temperature was performed first to investigate the temperature distribution within the concrete slab. Subsequently, the wave refraction technique was numerically simulated to evaluate the damage depth of the concrete slab. According to the refracted wave propagation path, a simplified procedure is proposed for the detection of the damage depth of concrete under high temperature. In the simplified procedure, a receiver is placed at an adequate distance from the impact source so that the first arrival wave at the receiver will be a wave refracted from the interface between the damaged layer and the sound layer inside the concrete. To verify the applicability of the proposed simplified procedure, concrete slab specimens subjected to an elevated temperature of 600 °C were tested in this study. The experimental results indicate that the simplified method proposed in this paper can indeed be used to detect the depth of high-temperature damage in concrete. In addition, the experimental results show that under the same high-temperature exposure conditions, the depth of fire damage increases with a decrease in the water-cement ratio. This can be attributed to the higher thermal conductivity coefficient of concrete with a lower water-cement ratio.

Overexpression of SlATG8f gene enhanced autophagy and pollen protection in tomato under heat stress.

Autophagy is a mechanism for the degradation of cellular components in eukaryotes and plays a critical role in plant responses to abiotic stress. As a core member of the autophagy process, ATG8's role in how plants respond to heat stress remains unclear. To investigate the response of the tomato autophagy core member ATG8f to heat stress, we studied the key gene ATG8f and generated tomato lines overexpressing SlATG8f using the recombinant expression vector pBWA(V)HS. We observed that under heat stress, SlATG8f overexpression (OE) plants exhibited decreased heat tolerance compared to wild-type (WT) plants. Specifically, OE plants showed increased relative electrolyte leakage, reduced soluble solid content, elevated chlorophyll content, and higher autophagosome numbers, with less damage to chloroplasts and mitochondria. Additionally, expression of some ATG8 family genes and heat shock protein-related genes was upregulated. Moreover, SlATG8f overexpressing plants had higher pollen vitality and more intact pollen morphology. These results suggest that while SlATG8f overexpression renders plants more sensitive to heat, it helps mitigate high-temperature damage to tomato pollen by maintaining chloroplast integrity and interacting with heat shock proteins to respond to heat stress.

Study on the high temperature performance of magnesium and potassium phosphate cement mixed with sucrose and its mechanism of action

Magnesium potassium phosphate cement (MKPC) is susceptible to high-temperature damage when used as a fireproofing coating or structural repair material and as a nuclear waste encapsulation shell, and the strength loss and dimensional shrinkage at about 100 °C severely limit the application of MKPC. Therefore, in this paper, the macroscopic properties, physical phase composition and microscopic morphology of sucrose-modified MKPC at room and high temperatures (20°C, 50°C, 120°C) are investigated from the perspective of modified retarder, and the mechanism of sucrose's influence on MKPC at high temperatures and the optimal dosage are speculated, and the Pearson correlation analysis is performed on the various macroscopic and microscopic indexes. The results showed that 2.5 % sucrose doping could reduce dimensional shrinkage by 59.6 % and increase late strength by 21.8 % at high temperatures, significantly optimizing the macroscopic properties of MKPC. The inhibition of the high-temperature decomposition product MgKPO4·H2O by sucrose and the reduction of pores formed by water evaporation are among the main reasons for the optimization of the properties. Additionally, the adsorption of amorphous products to form new polymers that fill the pores is also an important reason for the optimization of performance. However, Pearson's correlation analysis showed that too much sucrose contributed to the reduction of pulp strength, and its optimal dosage should be between 2 % and 3 %.

Experimental research of corroded concrete beams with natural cooling after fire considering the bond deterioration

The residual bearing capacity after fire is of great significance for safety assessment and repair of building structures. To accurately evaluate the residual strength of corroded beam after natural cooling, this study investigated the residual bearing capacity of corroded beam considering the bond deterioration after fire exposure. First, the bond behavior and flexural-deformation capacity was conducted by pullout test and bending test after corrosion erosion and fire temperatures damage. The bond deterioration test shows that when the temperature rises above 200℃ and the corrosion level exceeds 4.3%, the bond strength decreases by 16.5%. At the temperature reaches 600℃ or the corrosion degree reaches 13.8%, the bond behavior damage exceeds 50%. The bending test indicates that corrosion and high temperature damage both decrease the bending bearing capacity of the beam, but the influence of high temperature damage on the residual bearing capacity is greater than that of corrosion. The bond property deterioration decreases the strain value of the tensile rebar during the bending process, and decreases the bending capacity of the beam. Finally, a bond-slip constitutive model suitable for corroded beams after fire is proposed, which is applied to the calculation of the ultimate moment of the beam. The modified value of beam bearing capacity considering bond deterioration has better collimation and higher safety margin. The bond-slip constitutive model and the modified calculation method of bending moment of beam are helpful to provide more accurate performance assessment of beam after the coupling effect of corrosion and fire damage.

Study on dynamic mechanical properties and microscopic damage mechanisms of granite after dynamic triaxial compression and thermal treatment

As underground mining operations gradually extend deeper, the conditions for orebody occurrence become increasingly complex, and various geological disasters occur frequently. Rock masses are prone to different degrees and types of damage, making it impractical to continue using intact rock as a reference. To study the dynamic mechanical properties of damaged rock under actual conditions, this study subjected granite samples to impact and high-temperature damage. Detailed observations were made of the samples' surface morphology and microstructure before and after damage, and the patterns of damage changes were investigated. Subsequently, uniaxial compression tests at different loading rates were conducted on the damaged samples. By calculating the loading rate effect sensitivity, it was found that as the damage increased, the rate effect gradually diminished. In addition, this study also summarized the influence of damage and loading rate on the macroscopic failure characteristics of the samples. The novelty of this study lies in focusing on damaged rock, which more closely resembles the actual rock conditions encountered in most underground mining operations today. This research can provide a reference for stability assessment and safe construction in deep mining rock engineering and offers important insights into the feasibility of non-explosive extraction of damaged rock.

Synergistic Effect of Blended Precursors and Silica Fume on Strength and High Temperature Resistance of Geopolymer.

This paper investigates the high temperature resistance performance and mechanism of potassium-activated blended precursor geopolymer with silica fume. The failure morphology, volume, and mass loss, compressive strength deterioration, hydration production, and pore structure are measured and analyzed. The results show that introducing slag into fly ash-based geopolymer could greatly improve the 28 d compressive strength but reduce the thermal stability. In contrast, the partial substitution of fly ash by metakaolin contributes to excellent high temperature resistance with slightly enhanced 28 d compressive strength. After being exposed at 800 °C, the residual compressive strength of F7M3 remains at 37 MPa, almost 114% of the initial ambient-temperature strength. An appropriately enlarged silica fume content in geopolymer results in increased compressive strength and enhanced thermal stability. However, an excessive silica fume content is detrimental to the generation of alkali-aluminosilicate gels and ceramic-like phases and thus exacerbates the high temperature damage.

Temperature-dependent creep damage mechanism and prediction model of fiber-reinforced phenolic resin composites

Carbon fiber-reinforced phenolic resin (CF/PF) and glass fiber-reinforced phenolic resin (GF/PF) composites are crucial for thermal insulation and load-bearing capabilities in the aerospace industry. Understanding their creep behavior at various temperatures is essential. This study investigates the impact of temperature on the bending creep properties of CF/PF and GF/PF composites, focusing on deformation response, damage mechanisms, and prediction models. Results reveal that the decrease in creep properties at elevated temperatures is mainly attributed to the increased viscoplastic strain. At room temperature, CF/PF composite demonstrates exceptional creep properties. CF/PF composite exhibits heightened sensitivity to elevated temperatures, undergoing creep rupture at 210 °C and 240 °C with failure strains of 0.48 % and 0.49 %, respectively. High-temperature damage mechanisms have been analyzed in depth using a combination of thermal stress finite element simulation and microscopic characterization. Thermal stress is directly related to the difference in thermal expansion between the fibers and the resin. The influence of fiber distribution and geometry results in the interface being subjected to both normal and shear stresses. The accumulation of interfacial damage increases the plastic deformation and degrades creep performance. Additionally, an advanced temperature-dependent Burgers model has been developed and effectively predicted the creep curves under different temperatures and loads. This model demonstrated great potential as a general predictive model.

Research on high-temperature mechanical behaviour of carbon/phenolic composites under ultra-high heating rates

Fibre-reinforced resin matrix composites exhibit excellent resistance to ablation, thermal insulation and mechanical properties at high temperatures, making them widely used in aerospace engineering. Needle-punched reinforced carbon/phenolic composites are the most commonly used structural material for solid rocket engine nozzles. However, during the working process of the engine, the mechanical behaviour under ultra-high heating rates is difficult to characterise due to extreme loads. Therefore, in this study, specimens were carbonised before testing, and an electric heating testing machine was combined with an infrared thermal imager and digital image correlation system to characterise the mechanical behaviour of carbon/phenolic at ultra-high heating rates. The results indicate that at a heating rate of 200 °C/s, the compressive modulus increases linearly with temperature, reaching 63.1 GPa at 1400 °C. The maximum compressive strength is 61.9 MPa at 1400 °C, while the minimum is 27.4 MPa at 600 °C. Referring to the high-temperature damage constitutive model, a pyrolysis damage high-temperature strengthening constitutive model was constructed, accurately describing the in-plane compression mechanical behaviour of carbon/phenolic composites.

Temperature-dependent damage of magnesium alloy with ratchetting–fatigue interaction effects: Experiments and mesomechanical theory

Fatigue failure is a significant concern for magnesium (Mg) alloy components. However, fatigue damage mechanisms of Mg alloys, particularly in the case of ratchetting–fatigue interaction at elevated temperatures, are still not well understood. In this paper, we combine experiments and theoretical analysis to investigate the high-temperature damage mechanisms of the extruded AZ31 Mg alloy, specifically focusing on the effects of ratchetting–fatigue interaction. We reveal a distinct demonstration of damage, namely the formation of microvoids in the alloy due to significant ratchetting deformation, defined as ratchetting damage. Notably, this ratchetting damage is more prevalent at higher temperatures. Considering the mesomechanics-based energy mechanisms associated with grain boundaries (or twin boundaries), a mesomechanical damage model is established to capture the ratchetting damage under elevated temperatures and large ratchetting deformations. This model can reasonably simulate the intricate process of damage evolution and predict the critical condition of microvoid or microcrack formation. This work has the potential to serve as a theoretical tool for the safety design of structures made from Mg alloys under complex mechanical and thermal conditions.

High-Efficiency Thermal-Shock Resistance Enabled by Radiative Cooling and Latent Heat Storage.

Radiative cooling technology is well known for its subambient temperature cooling performance under sunlight radiation. However, the intrinsic maximum cooling power of radiative cooling limits the performance when the objects meet the thermal shock. Here, a dual-function strategy composed of radiative cooling and latent heat storage simultaneously enabling the efficient subambient cooling and high-efficiency thermal-shock resistance performance is proposed. The electrospinning and absorption-pressing methods are used to assemble the dual-function cooler. The high sunlight reflectivity and high mid-infrared emissivity of radiative film allow excellent subambient temperature of 5.1°C. When subjected the thermal shock, the dual-function cooler demonstrates a pinning effect of huge temperature drop of 39°C and stable low-temperature level by isothermal heat absorption compared with the traditional radiative cooler. The molten phase change materials provide the heat-time transfer effect by converting thermal-shock heat to the delayed preservation. This strategy paves a powerful way to protect the objects from thermal accumulation and high-temperature damage, expanding the applications of radiative cooling and latent heat storage technologies.

An NIR-II-enhanced nanozyme to promote wound healing in methicillin-resistant Staphylococcus aureus infections

Deep tissue bacterial infections, especially methicillin-resistant Staphylococcus aureus (MRSA) infections, pose challenges to clinical therapy due to their low debridement efficiency and relapsing. Molybdenum disulfide (MoS2) is used in the antibacterial field as a classic photothermal agent (NIR-I) with good biocompatibility. However, due to its limited NIR-I tissue penetration ability and single treatment mode, MoS2 has poor therapeutic effects on deep tissue infection. Herein, we prepared a defect-type hybrid 2H-MoS2 nanozyme (MoWS2) using hydrothermal method fabricate the MoWS2 composite, which is a new antibacterial strategy involving photothermal and enzyme catalysis, and further enhances the activity of the nanozyme through overheating. The regulation of 2H-MoS2 defects through tungsten ion doping endows MoWS2 with better near-infrared two-region absorption (NIR-II) and enzyme catalytic performance. Antibacterial activity experiments in vitro have shown that MoWS2 can achieve efficient bactericidal activity and biofilm clearance through hyperthermia and reactive oxygen species (ROS). Deep MRSA infection experiments have shown that MoWS2 rapidly removes bacteria from subcutaneous infected tissues through photothermal therapy (PTT) and chemodynamic therapy (CDT), accelerates the dissipation of abscesses, and promotes the healing of infected wounds. Additionally, the versatile treatment mode of MoWS2 was further confirmed through tissue sectioning and immunofluorescence staining analysis. Overall, these results provide a feasible approach for achieving efficient treatment of deep tissue infections through tungsten ion doping to regulate defective 2H-MoS2. Statement of significanceThe photothermal effect of MoS2 nanosheets in the NIR-I (650-900 nm) window in anti-MRSA therapy is considered to be highly reliable and efficient in PTA. However, most of the developed PPT therapies or antimicrobial systems based on PTT therapies developed with 1T-MoS2 have in vivo sterilization temperatures of more than 55°C, which have the risk of damaging the normal tissues of the skin. In this study, we prepared W@MoS2 with a good photothermal effect (36.9%) in the NIR-II window and good peroxidase-like activity. The combined effect of PTT and CDT has a stronger bactericidal effect while avoiding high-temperature damage, which makes the W@MoS2 material more advantageous in terms of antimicrobial effect.

Prediction of ductile cracking in the titanium alloy forging process

Abstract The control of surface cracking in the forming of titanium alloy forgings is a significant problem in the forging industry. For titanium alloys, the formation of surface cracks is related to temperature, strain rate, and stress state. This study selected the widely used medium to high strength titanium alloy Ti-6Al-4V in the field of forging as the research material, and designed six different shapes of specimens for high-temperature tensile and compression tests. The mechanisms underlying crack formation were analyzed at the microscopic level, and the critical fracture displacement of these tests was extracted. Moreover, their critical fracture strains were obtained through simulations, and a High-temperature damage model was established based on the DF2016 model. The research results showed that cracks through void at grain boundaries propagate and aggregate to form, leading to a fracture mechanism characterized by ductile fracture through micro-pore aggregation. Simulation results demonstrate that the established model accurately predicts the crack of forgings.

Increased panicle nitrogen application improves rice yield by alleviating high-temperature damage during panicle initiation to anther development.

The grain yield is closely associated with spikelet fertility in rice (Oryza sativa L.) under high temperatures, and nitrogen (N) plays a crucial role in yield formation. To investigate the effect of panicle N application on yield formation under high temperatures at the panicle initiation stage, two rice varieties [Liangyoupeijiu (LYPJ, heat susceptible) and Shanyou63 (SY63, heat tolerant)] were grown and exposed to high daytime temperature (HT) and control temperature (Control) during the panicle initiation stage. Low (LPN) and high (HPN) panicle N applications were conducted. HT markedly decreased the yields by 87% at LPN and 48% at HPN in LYPJ and 31% at LPN and 36% at HPN in SY63. The decrease in grain yield under HT was primarily attributed to the decline in spikelet fertility, HPN increased spikelet fertility. HT resulted in the abnormal development of anthers, which included disordered, enlarged, and broken anther wall layers, degraded and irregularly shaped microspores, delayed tapetum degradation, less vacuolated microspores per locule, abnormal and aborted pollen grains; however, HPN improved the development of anthers under HT, particularly in LYPJ. A high rate of evapotranspiration resulted in an approximately 1°C decrease in panicle temperatures at HPN compared with that at LPN in both varieties under HT. Overall, these results demonstrate that the increased panicle N application favors normal anther development in LYPJ by decreasing the panicle temperature, which results in high pollen viability and spikelet fertility, and consequently less yield loss under HT.

Applying Microbial-Induced Calcium Carbonate Precipitation Technology to Improve the Bond Strength of Lightweight Aggregate Concrete after High-Temperature Damage

High temperatures and external force can easily lead to a decline in the bond strength of reinforced concrete components. Microbial-induced calcium carbonate precipitation (MICP) technology has considerable potential for repairing concrete. Given this, this study utilized MICP technology to improve the bond strength of heat- and pull-damaged lightweight aggregate concrete (LWAC). The specimens of a control group (Group A) and two experimental groups (Group B and Group C) were prepared. The experimental group was prepared using lightweight aggregates (LWAs) that had been immersed in a nutrient solution and a bacterial solution. The control group was prepared using LWAs that were not immersed in a nutrient solution or bacterial solution. These specimens healed themselves in different ways after exposure to high temperatures (300 °C and 500 °C) and pull-out damage. Groups A and B adopted the same self-healing method; that is, their specimens were placed in a computer-controlled incubator at 40 °C. Group C used different self-healing methods. The specimens in this group were soaked in a mixed solution of urea and calcium acetate at 40 °C for two days and then taken out and placed in an incubator at 40 °C for two days. A cycle took four days until the expected self-healing age was reached. After being exposed to 300 °C and self-healed for 90 days, the residual bond strengths of the secondary pull-out tests in Groups A, B, and C were 20.63, 22.13, and 25.69 MPa, respectively. Moreover, compared with Group A, the relative bond strength ratios of the secondary pull-out tests in Groups B and C increased by 5.8% and 20.3%, respectively. This demonstrates that MICP technology could effectively improve the bond strength of LWAC after high-temperature and pull-out damage.

Rafting and redissolution of γʹ phase in Ni–Al alloy under external stress

The volume fraction and rafting degree of the γʹ-Ni3Al phase under stress and high temperature are the key characteristics of mechanical properties in Ni-based superalloys, the rafting and redissolution of γʹ phase caused by the creep at high temperature damage the morphology and properties of Ni-based superalloys. The phase-field simulation is performed to study the rafting accompany with the redissolution of γʹ phase under high temperature and loading stress in Ni–Al alloy, the driving force and kinetics evolution of the γʹ rafting were revealed. During the rafting under continuous heating, the elastic energy in the vertical γ channel is different to that of the horizontal γ channel, this difference in elastic energy drives the elements diffusion directionally to form the γʹ rafts morphology. With the increased tensile stress, the decrease of specific surface of the γʹ phase slows down the redissolution, a higher volume fraction is reserved for the rafted γʹ phase. With temperature increases, the interface of γ/γʹ phase becomes more diffusional and wider under stress. The results give an insight on the rafting mechanism of γʹ phase and the kinetics evolution in Ni-based superalloys under excess temperature.

Study of an integrated vortex tube used in hydrogen pre-cooling system

In hydrogen refueling stations, a hydrogen pre-cooling system is essential to protect the onboard hydrogen storage cylinder from high-temperature damage during refueling. To address the high power consumption of existing systems, this study proposes an integrated vortex tube hydrogen pre-cooling system. This system combines the vortex tube with a two-stage compression refrigeration cycle to create a new refrigeration device. The vortex tube component is numerically simulated using the standard k-ε turbulence model. Comparative analysis of power consumption and coefficient of performance (COP) is conducted between the new system, single-stage, and two-stage hydrogen pre-cooling systems. The results indicate that the vortex tube, as the pressure ratio increases from 1.5 to 20, reduces power consumption by 26.37%–41.52% compared to the single-stage system. Additionally, it improves the COP by 30.9%–53.8% compared to the single-stage system. Furthermore, compared to the two-stage system, the vortex tube achieves power savings of 4.08%–10.44% and COP improvements of 4.3%–11.7%.

Performance recovery of high-temperature damaged ultra-high-performance concrete under different curing environments

The self-healing capability and susceptibility to salt solution erosion in ultra-high-performance concrete (UHPC) significantly influence the mechanical properties and long-term durability of concrete structures within coastal or underground environments. Acknowledging the intricacies of real-world environments, this study focuses on UHPC that has endured high-temperature damage at 800 °C. The research aims to analyze the property variations within 28 days following exposure to diverse dry and wet conditions, as well as salt solution environments. The findings demonstrate a substantial recovery in both mechanical and transport properties of the high-temperature-damaged UHPC, attributed to its inherent self-healing capability. Among the dry and wet conditions, the optimal performance recovery of UHPC specimens is observed when they are subjected to submerged and immersed environmental conditions. Furthermore, when immersed in a salt solution environment, the beneficial impacts attributed to the self-healing property tend to outweigh the detrimental effects of salt solution erosion. All scenarios exhibit a trend of enhanced properties, with the presence of chloride salts being particularly conducive to the recovery process. However, exposure to a sulfate-rich environment induces deterioration in transport properties and pore structure, resulting in a partial incongruity with the mechanical property results. Microscopic analysis techniques reveal that the primary contributors to enhanced properties encompass a range of hydration products formed due to the interaction between water, salt solutions, and the compromised UHPC. Nevertheless, owing to the intricate nature of the environment, disparities arise in both the type and quantity of hydration products, contributing to variations in the extent of property alterations.

Microscopic characteristics and thermodynamic property changes in limestone under high-temperature treatment

This article combines X-ray diffraction (XRD) analysis of limestone after high-temperature treatment with microscopic structural characteristics. It aims to elucidate the changes in diffraction peak characteristics from a microscopic perspective and investigate the thermodynamic property variations of the material. The research findings indicate that 500 °C is the threshold temperature at which limestone's crystalline orientation and spatial arrangement change, resulting in a decrease in peak height in the diffraction pattern. Additionally, temperatures ranging from 500 to 600 °C accelerate particle thermal motion, leading to the detachment of rock layers, the inward extension of fissures, and the formation of a sedimentary rock-like 'layered' stacking structure. The thermal conductivity, specific heat capacity, and heat storage coefficient of limestone gradually decrease after thermal treatment, with a reduction rate of approximately 3 % per 100 °C. The microstructural characteristics and thermodynamic property changes of high-temperature limestone reveal the impact of high-temperature damage on limestone structure and thermodynamic properties, facilitating the advancement of limestone material applications and damage control under high-temperature conditions.