Micromechanical and Microstructural Analysis of Lunar Concrete

This research investigates the microstructure and micromechanical properties of geopolymer concrete made from lunar regolith simulant, a promising in situ resource utilization (ISRU) technology for lunar construction. Limited availability and high cost of lunar simulants hinder the study of macroscale properties of lunar concrete, so the material is studied at microscale to obtain basic information about its properties and expected performance. We produced lunar concrete by activating Off-Planet Research’s H2N lunar highland simulant with a sodium silicate solution at standard temperature, pressure, and gravity. Through a central composite design, we altered the solution/simulant ratio, silica modulus, and curing temperature. We measured compressive strength using miniature cylinders and used nanoindentation and scanning electron microscopy to characterize the micromechanical properties and microstructure. The results suggest that the bulk properties of the material are indirectly related to solution/simulant ratio and curing temperature, and directly related to silica modulus. The micromechanical properties of the reaction products closely resemble those in terrestrial geopolymers, and the bulk of the unreacted simulant has mechanical properties resembling those of terrestrial aggregates.