Synthesis and characterization of geopolymer from lunar regolith simulant based on natural volcanic scoria

In this study, a new GVS (Ground Volcanic Scoria) lunar regolith simulant was produced. The similarity between GVS and lunar soil was proved by comparison with Apollo lunar soil samples and other commercial lunar soil simulants. Then, GVS lunar regolith simulant was investigated as the source material for preparing geopolymer to produce building material for lunar colony construction. To study the possibility of preparing geopolymer from GVS lunar regolith simulant and the optimum activator formulation as well as the optimum curing conditions, alkaline activated GVS slurries with different mixing ratios based on an orthogonal test scheme were prepared. The geopolymer products based on GVS were characterized by flexural strength test, compressive strength test, X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope coupled with Energy Dispersive Spectroscopy (SEM-EDS), ²⁹Si magic angle spinning-nuclear magnetic resonance (²⁹Si MAS-NMR), and ²⁷Al MAS-NMR. The experimental results indicate that changes in the mass ratio of sodium hydroxide and GVS and curing temperature have the most significant influence on the flexural strength and compressive strength, respectively. The GVS-based geopolymer can obtain the highest 28-day compressive strength and 28-day flexural strength up to 75.6 MPa and 6.3 MPa. Microstructural results imply that the changes of Si occurring in a variety of environments that explaining preliminarily about the reaction mechanism of GVS-based geopolymer. This study approves the feasibility of making a geopolymer derived from the GVS lunar regolith simulant and the potential utilization of geopolymer based on lunar regolith for construction of the lunar colony in future space exploration.