In situ resource utilization of lunar regolith provides a cost-effective way to construct the lunar base. The melting and solidifying of lunar soil, especially under the vacuum environment on the Moon, are the fundamentals to achieve this. In this paper, lunar regolith simulant was melted and solidified at different temperatures under a vacuum, and the solidified samples' morphology, structure, and mechanical properties were studied. The results indicated that the density, compressive strength, and Vickers hardness of the solidified samples increased with increasing melting temperature. Notably, the sample solidified at 1400 degrees C showed excellent nanohardness and thermal conductivity originating from the denser atomic structure. It was also observed that the melt migrated upward along the container wall under the vacuum and formed a coating layer on the substrate caused by the Marangoni effect. The above results proved the feasibility of employing the solidified lunar regolith as a primary building material for lunar base construction.

The utilization of lunar in-situ resources is an important way to realize the construction and operation of Moon scientific research base. The effect of alumina-alkali activator on the mechanical properties of solidified lunar soil simulant was studied by using basaltic lunar soil simulant as raw material, adding alumina and alkali activator for solidification treatment. Characterisation of hydration products in the simulated lunar soil using X-ray diffraction (XRD), scanning electron microscopy with energy spectroscopy (SEM-EDS), fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG-DTG) and X-ray photoelectron spectroscopy (XPS). The solidified mechanism of lunar soil simulant under the synergistic effect of aluminaalkali activator was discussed. The results showed that the compressive strength and splitting tensile strength of the solidified lunar soil simulant show an increasing trend, and the highest compressive strength was 17.29 MPa, which was 57% greater than that of the control group. The energy evolution process inside the specimen can be divided into four stages: damage initiation, damage increase, damage mutation and damage acceleration. The incorporation of alumina can promote the geopolymerization reaction between the alkali activator and the lunar soil's mineral composition to generate plenty of (N,C)-A-S-H gels that can fill the pores in the particles, thereby improving the mechanical strength of the solidified lunar soil simulant. Finally, the microscopic reaction mechanism model of alumina-alkali activator synergistic solidified lunar soil simulant was established.

The development and utilization of lunar resources are entering a critical stage. Immediate focus is needed on key technologies for in-situ resource utilization (ISRU) and lunar base construction. This paper comparatively analyzes the basic characteristics of lunar regolith samples returned from Chang'e-5 (CE- 5), Apollo, and Luna missions, focusing on their physical, mechanical, mineral, chemical, and morphological parameters. Given the limited availability of lunar regolith, more than 50 lunar regolith simulants are summarized. The differences between lunar regolith and simulants concerning these parameters are discussed. To facilitate the construction of lunar bases, this article summarizes the advancements in research on construction materials derived from lunar regolith simulants. Based on statistical results, lunar regolith simulant-based composites are classified into 5 types by their strengthening and toughening mechanisms, and a comprehensive analysis of molding methods, preparation conditions, and mechanical properties is conducted. Furthermore, the potential lunar base construction forms are reviewed, and the adaptability of lunar regolith simulant-based composites and lunar base construction methods are proposed. The key demands of lunar bases constructed with lunar regolith-based composites are discussed, including energy demand, in-situ buildability, service performance, and structural availability. This progress contributes to providing essential material and methodological support for future lunar construction. (c) 2024 Published by Elsevier B.V. on behalf of China University of Mining & Technology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Establishing a base on the Moon is one of the new goals of human lunar exploration in recent years. Sintered lunar regolith is one of the most potential building materials for lunar bases. The physical, mechanical and thermal properties of sintered lunar regolith are vital performance indices for the structural design of a lunar base and analysis of many critical mechanical and thermal issues. In this study, the HUST-1 lunar regolith simulant (HLRS) was sintered at 1030, 1040, 1050, 1060, 1070, and 1080 C. The effect of sintering temperature on the compressive strength was investigated, and the exact value of the optimum vacuum sintering temperature was determined between 1040 and 1060 C. Then, the microstructure and material composition of vacuum sintered HLRS at different temperatures were characterized. It was found that the sintering temperature has no significant effect on the mineral composition in the temperature range of 1030-1080 C. Besides, the heat capacity, thermal conductivity, and coefficient of thermal expansion (CTE) of vacuum sintered HLRS at different temperatures were investigated. Specific heat capacity of sintered samples increases with the increase of test temperature within the temperature range from -75 to 145 C. Besides, the thermal conductivity of the sintered sample is proportional to density. Finally, the two temperatures of 1040 and 1050 degrees C were selected for a more detailed study of mechanical properties. The results showed that compressive strength of sintered sample is much higher than tensile strength. This study reveals the effects of sintering temperature on the physical, mechanical and thermal properties of vacuum sintered HLRS, and these material parameters will provide support for the construction of future lunar bases. (c) 2024 Published by Elsevier B.V. on behalf of China University of Mining & Technology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).