Carbon Nanotube Reinforced Lunar-Based Geopolymer: Curing Conditions

Current space exploration focuses on returning to the Moon to expand space exploration capacity by improving technology. The long-term presence of humans and robots on the Moon requires the development of durable habitats for space missions. In recent decades, in situ resource utilization (ISRU) for construction materials has been recognized as a viable option. However, the addition of nanomaterials, which exhibit a high strength-to-weight ratio, has not been incorporated with the ISRU framework in space missions. This paper investigates the impact of carbon nanotubes (CNTs) on lunar simulant-based geopolymers’ compressive strength and water retention. The evaluation of water retention indicates another potential in water recapturing capability. In this study, CNTs can enhance the mechanical properties of lunar simulant-based geopolymer. Two lunar simulants were used, representing the Highland and Mare regions of the Moon. Experimental variables included CNT concentration, four curing regimes (ambient curing, two oven-curing methods, and microwave radiation), and dispersion time in aqueous solutions. Results showed that CNTs can positively influence both strength gain and water retention during curing regimes, but the extent of influence appears to be dependent on simulant type and curing regime. The Highland simulant consistently outperformed the Mare simulant in oven-curing regimes from a strength perspective, regardless of CNT presence. The strength benefits of CNTs were more pronounced at ambient curing temperatures. Even under poor curing conditions—where water availability may be limited at temperatures of 80 °C—CNTs aid in retaining water within the geopolymer matrix, leading to improved strength compared to counterparts. Under the same conditions, a higher concentration of CNTs further confirmed their role in water retention during geopolymerization, with consistently greater water retention observed in samples containing CNTs. Additionally, microwave radiation was explored as an alternative to conventional oven drying, showing potential for reducing curing duration. Finally, the findings suggest that combining CNTs and microwave radiation could enhance water recovery and reuse, contributing to the development of high-strength infrastructure materials on the Moon with reduced energy and cost requirements.