Development of composition-property relationships for lunar regolith simulant geopolymers

• Meredith Rodney, Chemical Engineering, University of Delaware

• William Hartt, Norman J. Wagner, University of Delaware

In the past decade, there has been a resurgence in interest in space and extraterrestrial habitation. This is present in the United States with NASA’s Project Artemis, with a drive for a sustained human presence on the moon. To achieve this, habitats, landing pads, storage facilities and more will need to be constructed near the lunar surface. Traditional construction methods, however, are ineffective due to payload limitations, lunar regolith composition, and the harsh lunar atmosphere. In order to feasibly create structures on the moon, an alternative construction method with in-situ resource utilization (ISRU) will be required. Geopolymers offer an opportunity for this application. Geopolymers are inorganic amorphous aluminosilicate polymers created from an aluminosilicate source and a sodium silicate activating solution. These materials have been shown to possess similar material properties to modern cements. Mills et al. has shown that lunar and Martian regolith simulants can support geopolymer formation due to their high amounts of silicon and aluminum oxides, and Egnaczyk et al. has shown the compositional dependence on the material properties of lunar mare regolith simulants is complex. It is thus critical to expand and extend compositional relationships to other lunar regolith simulant geopolymer materials.

This work explores the impact of geopolymer composition and aluminosilicate particle size on LHS-1 Lunar Highlands Simulant geopolymers. The 7-day compressive strength of these materials was investigated for geopolymers created with varying aluminosilicate source weight percents (55, 60, 65, 70, and 75wt%) as well as varying sodium silicate activating solution concentrations (60wt% water with molar ratios of Si/(Si+Na) = 0.3, 0.4, 0.5, and 0.6). Each compositional series was explored for unaltered LHS-1 as well as LHS-1 sieved below 75µm. Developing composition-property relationships for geopolymers across varying aluminosilicate compositions is crucial for the intelligent design of geopolymer materials for lunar construction.