Fiber-reinforced lunar geopolymers synthesized using lunar regolith simulants

Abstract

In-situ resource utilization is extremely important to not only support additive construction on the Moon but also to minimize the weight of transportation. The work outlined in this study presents a possible solution to supporting lunar additive construction by the formulation of fiber-reinforced geopolymers using lunar regolith simulants. Two types of regolith simulants were utilized to synthesize the fiber-reinforced geopolymers developed in this study (i.e., Lunar Mare Simulant (LMS-1) and Lunar Highlands Simulant (LHS-1)). The material properties and variables investigated were the simulant type, flowability, the effect of curing temperature on compressive strength, fiber type, and flexural strength. The results were supplemented with chemical and microstructural analysis. It was observed that the LHS-1 geopolymer exhibited higher compressive strength compared to that of the LMS-1 geopolymer. High-temperature curing at 93 °C and 5 % RH for 72 h was found to show a significant strength development on the LHS-1 geopolymer. However, the LMS-1 geopolymer did not show any significant strength development irrespective of curing conditions. The combination of equal proportions of LMS-1 and LHS-1 produced a geopolymer with a flow value of 94 mm, compressive strength of 29.75 MPa, and flexural strength of 2.32 MPa when cured at high temperatures. Adding basalt fibers and human hair fibers improved the flexural strength by up to 32 % and 15 %, but reduced the compressive strength. This is validated by SEM analysis which confirms that the fibers act as nucleation sites to significantly improve the flexural strength and microstructure of the lunar geopolymer.