Basalt fiber reinforcement mechanism for geopolymer exposed to lunar temperature environment

The construction of a lunar base is deemed a significant move for mankind's exploration into deep space. Geopolymer solidification is considered as an effective technique for regolith to achieve promising mechanical properties, while extreme temperature on the lunar surface could negatively affect the mechanical properties of geopolymer samples. In this study, a new lunar regolith simulant and basalt fiber were used to develop geopolymer samples with various fiber dosages of 0 %, 0.3 %, 0.7 %. These samples were cured at temperature approaching actual lunar surface temperatures at recommended locations (-196 degrees C-118 degrees C) for 3d, 7d, 14d, and 28d. A range of tests were conducted on geopolymer samples to study the effects of fiber dosage and curing condition, including P-wave, compressive strength, flexural strength, AE, SEM-EDS, FTIR, and XRD. The addition of 0.3 % fiber into the samples results in an increase of tensile cracking, while the addition of 0.7 % fiber induces an increase in shear cracking within the samples. These findings, corroborated by SEM observations, substantiate the mechanism of fiber clustering and bridging. High-temperature curing is beneficial for the geopolymerization, it also results in zeolite products and higher growth rate of N-A-S-H gel while low-temperature causes some degradation. High rates of temperature change can cause thermal stress cracks, which also degrade the geopolymer. With an increase in curing time, the geopolymer samples exhibit a higher quantity of N-A-S-H gel and higher cross-linked C-N-A-S-H gel.