Decoding Freeze-Thaw Impacts: Multi-Scale Crack Propagation and Failure Precursors in Sandstone

Rocks are constantly under pressure especially in regions where temperatures swing between freezing and thawing. Water seeps into tiny cracks, freezes, expands, and then thaws, weakening the rock from the inside. Over time, this continuous cycle causes cracks to grow and materials to break apart, and even leads to complete structural failure. While it is a natural phenomenon, it is also a significant problem for people trying to protect infrastructure and historic landmarks. Ancient monuments especially those made of sandstone, are particularly vulnerable. This kind of sandstone, found in many Chinese cultural sites, faces steady degradation because of the freeze-thaw effect. Balancing the preservation of these historical structures with the demands of modern infrastructure requires a deep understanding of how this process works and although a lot of research has already been done on how freeze-thaw cycles affect rocks and looked carefully on  effect of moisture, the number of cycles, and temperature ranges, however, the rate at which the temperature changes has not been investigated before. Nature does not work at a single temperature change rate—some regions see temperatures shift gradually, while others experience rapid changes within hours. These variations can make a big difference in how rocks respond, but they have not been studied in enough detail. On top of this, the traditional tools used to assess rock damage, like infrared scanning, can be expensive or unreliable in real-world situations. This left a gap that needed to be filled. To this account, new research published in Journal of Fatigue & Fracture of Engineering Materials & Structures and led by Professor Chengyu Liu from Fuzhou University and PhD student Daozhe Zheng from Royal Melbourne Institute of Technology in Australia, alongside Professor Annan Zhou from Royal Melbourne Institute of Technology in Australia, Dr. Xiangxiang Zhang and Engineer Chenghai Chen from Fuzhou University, and PhD student Shengfeng Huang from Stevens Institute of Technology in the USA. The research team investigated how different temperature change rates during freeze-thaw cycles affect sandstone, particularly its mechanical strength and the way cracks form and grow. Using advanced tools, they tracked how cracks developed over time, providing an in-depth look at how sandstone behaves under these unique conditions.

The researchers started with cylindrical sandstone samples, polishing the surfaces to remove any imperfections to ensure consistency in the results. The samples were then placed in a custom-designed temperature chamber where the conditions could be carefully controlled. Temperatures ranged from -30°C to 30°C, and the rate of change varied from a slow 0.1°C per minute to a rapid 3°C per minute. Before every freeze-thaw cycle, the samples were soaked in distilled water to mimic natural saturation conditions. This setup let the team replicate real-world environments while closely observing the effects on the rocks. The authors found that the faster the temperature changed, the quicker the sandstone weakened. Its strength and elasticity dropped sharply, and it became more likely to deform under stress. At slower temperature change rates, the rock mainly developed tensile cracks—caused by pulling forces. But at faster rates, the rock experienced a mix of tensile and shear cracks, the latter caused by sliding forces. These findings showed that rapid temperature swings created more stress inside the rock, making it more prone to complex and interconnected fractures. Additionally, the team used acoustic emission (AE) and microseismic (MS) monitoring to understand how cracks formed. AE technology captured high-frequency signals from tiny cracks as they formed, giving the team a step-by-step view of crack development. They observed three distinct stages: initial compaction, stable crack growth, and rapid propagation. Faster temperature changes caused these transitions to happen earlier, meaning cracks grew and spread more quickly. MS monitoring, which focuses on larger cracks, confirmed that rapid temperature changes also accelerated the formation of significant fractures, the kind that often led to complete structural failure.

Furthermore, the authors were able to classify cracks based on their type and size and with the use of advanced analysis techniques, indeed,  the authors distinguished between tensile cracks and shear cracks, and they tracked how their proportions shifted depending on the rate of temperature change. Slower temperature shifts led to more tensile cracks, while faster changes caused a rise in shear cracks. This level of detail is incredibly helpful for engineers, as it allows them to design specific solutions to address different types of rock damage. The implications of this research are significant. Freeze-thaw cycles do not just impact rocks in natural landscapes—they also affect historical landmarks, many of which are made of sandstone. Over the years, the repeated freezing and thawing of water inside these stones creates stress, leading to cracks that can eventually cause irreparable damage. This study offers new tools for conservationists to identify early signs of deterioration and take action to protect these priceless cultural treasures. By understanding the early warning signs and thresholds where cracks become unstable, conservationists can act before the damage becomes too severe.

In conclusion, the work of Professor Chengyu Liu and colleagues successfully bridges the gap between small-scale cracks and large-scale structural failures. By combining data from AE and MS monitoring, the researchers painted a full picture of how cracks progress from tiny fractures to major breakages. These findings are critical for the mining, construction, heritage protection and tunneling industries where rock stability is important. Moreover, the ability to monitor cracks in real-time and predict failures can make a huge difference in managing risks and preventing disasters.