Mechanical and microstructural performance of LHS-1E-based geopolymer concrete subjected to thermal curing conditions

The utilisation of lunar regolith simulants (LRS) for the production of geopolymer concrete offers a promising approach for future lunar construction, as the essential raw materials, silica-alumina, alkali activators, and water, can potentially be derived from lunar in-situ resources. This study examines the synthesis and performance of geopolymer concrete produced from LHS-1E, a highland lunar regolith simulant, with a focus on curing regimes, activator chemistry, and fibre reinforcement. A conceptual solar-assisted curing scenario associated with near-continuous illumination at elevated south-polar ridges is considered as motivation for investigating elevated-temperature curing under controlled laboratory conditions. The curing trials showed that 93 °C for 8 days provided satisfactory strength development. The influence of NaOH molarity, partial-to-full replacement with sodium silicate, and the addition of 1% basalt fibre (by volume) was systematically assessed across ten mixtures using compressive, flexural, and tensile testing (three specimens per test), supported by elastic property evaluation and microstructural analysis. Results show that increasing NaOH molarity led to a gradual increase in strength, with a peak compressive strength of 15.3 MPa, whereas sodium silicate activation produced significantly higher compressive strength, achieving 44.0 MPa in the Na 2 SiO 3 -only formulation. Basalt fibre incorporation enhanced tensile and flexural performance through crack-bridging but reduced compressive strength due to fibre-matrix discontinuities. The findings demonstrate the potential of sodium-silicate-rich activations for enhanced mechanical performance of lunar geopolymer concretes and provide insights into curing strategies, activator selection, and fibre reinforcement for extraterrestrial applications.