Dynamic mechanical properties of lunar regolith based geopolymer: Coupled effects of composition and temperature

This study developed a high-fidelity lunar regolith simulant (GCD-2) that closely replicated the physicochemical properties of lunar samples retrieved by the Chang'e-6 mission. A lunar regolith based geopolymer (LRG) was subsequently synthesized using "one-part" method, in which a dry mixture of GCD-2 (as precursor) and solid sodium silicate (as activator) was combined with water. The dynamic mechanical properties of the LRG were then evaluated using the Split Hopkinson Pressure Bar (SHPB) apparatus. Systematic investigation was conducted to elucidate the influence of precursor Ca/Si and Al/Si ratios in lunar regolith simulant, as well as lunar thermal cycling, on the dynamic compressive strength and energy absorption capacity of the LRG. Two thermal curing regimes were designed to identify the optimal thermal curing window under lunar surface conditions. Microstructural evolution and porosity characteristics were examined using thermogravimetric analysis (TGA), X-ray diffraction (XRD), nitrogen adsorption–desorption (NAD), and scanning electron microscopy (SEM). The results demonstrated that increasing Ca/Si ratio to 0.35 markedly enhanced the degree of geopolymerization, promoting the formation of abundant C-(A)-S-H gel and resulting in a denser matrix with significantly improved dynamic elastic modulus and peak compressive strength. Adjusting Al/Si ratio to 0.50 facilitated the crosslinking of [AlO 4 ] units within the (C)-N-A-S-H gel network, further improving the dynamic mechanical performance. However, excessive Al/Si ratios hindered geopolymerization kinetics and increased porosity, thereby causing the reduction in the compressive strength of LRG. A synergistic effect between Ca and Al was observed, intensifying geopolymerization and yielding a highly compact microstructure with a peak dynamic compressive strength of 70.77 MPa and superior energy absorption capacity. Furthermore, the optimal time window for mixing and casting LRG on the lunar surface was determined to be within 100 h prior to the high-temperature phase of the lunar daytime. These findings provide both theoretical insights and practical guidance for the development of impact-resistant construction materials to support sustainable extraterrestrial habitat engineering. • Heating-phase curing enhanced strength via accelerated geopolymerization. • Moderate Ca/Si improved strength, modulus, and strain-rate sensitivity. • Al/Si showed nonlinear effects and excess Al reduced strength. • Ca–Al synergy maximized strength, modulus, and energy absorption.