The thermal stabilization of expansive soils has emerged as a promising and sustainable alternative to conventional chemical stabilization methods, addressing the long-standing challenges associated with soil swelling and shrinkage. This review critically evaluates the mechanisms, applications, and advancements in thermal stabilization techniques, with a particular focus on both traditional approaches (e.g., kiln heating) and emerging innovations such as microwave heating. This study synthesizes recent research findings to assess how thermal treatment modifies the mineralogical, physical, and mechanical properties of expansive soils, reducing their plasticity and improving their strength characteristics. Comparative analysis highlights the advantages, limitations, and sustainability implications of different thermal methods, considering factors such as energy efficiency, scalability, and environmental impact. While thermal stabilization offers a viable alternative to chemical treatments, key challenges remain regarding cost, field implementation, and long-term performance validation. The integration of thermal treatment with complementary techniques, such as lime stabilization, is explored as a means to enhance soil stability while minimizing environmental impact. By addressing critical research gaps and providing a comprehensive perspective on the future potential of thermal stabilization, this review contributes valuable insights for researchers and engineers seeking innovative and sustainable solutions for managing expansive soils.

The lunar poles potentially contain vast quantities of water ice. The water ice is of interest due to its capability to answer scientific questions regarding the Solar System's water reservoir and its potential as a useable space resource for the creation of a sustainable cislunar economy. The lunar polar water ice exists in extremely harsh conditions under vacuum at temperatures as low as 40 K. Therefore, finding the most effective technique for extracting this water ice is an important aspect of ascertaining the suitability of lunar water as an economically viable space resource. Based on previous work, this study investigates the impact of the different possible arrangements of icy regolith in the lunar polar environment on the suitability of microwave heating as a water extraction technique. Three arrangements of icy regolith analogues were created: permafrost, fine granular, and coarse granular. The samples were created to a mass of 40 g, using the lunar highlands simulant LHS-1, and a target water content of 5 wt %. The samples were processed in a microwave heating unit using 250 W, 2.45 GHz microwave energy for 60 min. The quantity of water extracted was determined by measuring the sample mass change in real-time during microwave heating and the sample mass before and after heating. The permafrost, fine granular, and coarse granular samples had extraction ratios of 92 %, 83 %, and 97 %, respectively. Possible explanations for the observed variations seen in the mass loss profiles of the respective samples are provided, including explanations for the differences between samples of varying ice morphology (permafrost and granular) and the differences between samples with varying ice surface areas (fine and coarse granular). While differences were observed, microwave heating effectively extracted water in all the samples and remains an effective ISRU technique for extracting water from icy lunar regolith. Differences in the water extraction of different icy regolith could be useful in determining the arrangement of ice in buried samples.

Addressing the challenges of wet and soft loess foundations is crucial in geotechnical engineering due to their inherent low strength and high compressibility. High-temperature sintering technology is a leading method for enhancing loess foundations, known for its fast processing and effective reinforcement. This paper focuses on the effects of saturation on the compressibility of sintered loess, using results from saturation and compression tests. It highlights how saturation influences loess differently under various sintering conditions. Particularly, loess sintered at 200 degrees C breaks down after saturation, losing its resistance to deformation. By contrast, loess sintered at other conditions retains some deformative resistance, but its compressibility still increases. The study finds an inverse relation between sintering temperature and the increase in compressibility after saturation. Additionally, it examines changes in compressibility indices, which include the compression coefficient, compression index, and modulus of compressibility. These are analyzed based on different saturation times, establishing a law that links saturation time to the compressibility of sintered loess.

Identifying the best technique for extracting water ice deposits in permanently shadowed regions at the lunar poles will be crucial in determining how successful a long-term or permanent settlement at these locations will be for future scientific and technology missions. This study uses a low-power microwave heating method to extract water from icy lunar simulants. Samples of lunar highland and mare simulants at different water contents (3-15 wt %) were heated using 250 W, 2.45 GHz microwaves. A maximum of 67 +/- 5% [2SD] of the water was extracted during heating runs of 25 min. Water was extracted more efficiently from the highland simulant than from the mare simulant. A significant reason for the different efficiency of water extraction in icy lunar simulants was the differing porosity of the samples made from different simulants. Pore space filled with ice leads to a reduced contact area between grains and an increased area of free ice, which causes poor heating performance. The results indicated that differences in chemical composition between the simulants had a negligible effect on water extraction, as the contact area between grains seems to dominate water extraction. This study found that low-power microwave heating is an effective technique for extracting water from cryogenic Icy simulants. It was also found that using a simple input energy principle (Input Energy = Absorbed Power x Heating Time) to es-timate the additional heating time was sufficient to overcome inefficient heating due to differing absorbed powers. For undersaturated samples, microwave heating was an efficient heating mechanism, but is less efficient for saturated samples where alternative heating methods may be more efficient at melting free ice before employing microwave heating.