Optimized manufacturing process of homogeneous microwave-sintered blocks of KLS-1 lunar regolith simulant

The use of materials from the Moon's surface based on In-Situ Resource Utilization (ISRU) is gaining considerable attention as a means of constructing infrastructure to sustain a human presence there. In particular, the sintering of lunar regolith appears a promising way to fabricate infrastructure on the lunar surface. This study presents a method to manufacture homogeneous blocks using a lunar regolith simulant. The tested simulant, KLS-1, was sintered under diverse conditions in a multi-mode microwave sintering furnace. Successful sintering requires the sample to be heated throughout, without generating a temperature gradient. This was achieved by testing various heating rates and sample sizes. X-ray computed tomography was used to assess the pore structure of sintered samples. While the optimized sintering conditions resulted in the formation of internal cracks by outgassing, preheating the KLS-1 in a vacuum oven at 250 °C effectively prevented the formation of internal cracks. The homogeneity of the blocks was confirmed by coring and measurements of true density, bulk density, porosity, and unconfined compressive strength. The robust reproducibility and similarity in physical and mechanical properties validate the viability of microwave sintering in manufacturing large and uniform blocks suitable for application as construction materials on the Moon.