The creation of secure and long-lasting surface outposts is a significant challenge for fu- ture crewed lunar missions. In-Situ Resource Utilization (ISRU) is a crucial strategy that can help lower mission costs and complexity by reducing the need to transport materials from Earth. Here, lunar regolith can be exploited to produce construction materials such as concrete and ceramics, enabling the fabrication of shielding structures, landing pads, and structural components. Geopolymers are a promising class of inorganic binders suit- able for lunar construction via additive manufacturing. In this study, low-water-content formulations were developed using aluminosilicate-rich lunar highlands regolith simulant activated with sodium hydroxide solutions. LHS-1-based mixtures were selected for de- tailed investigation due to their scientific relevance, with the dust fraction (LHS-1D) used as a rheological modifier to improve workability. Rheological properties relevant to printability and buildability were characterized by rotational rheometry under oscillatory conditions. The most promising formulations (LHS-D15-L34 and LHS-D20-L034) exhib- ited yield stress values between 1700 and 2500 Pa and viscosities comparable to reference cement systems, indicating compatibility with extrusion-based printing. Curing behaviour was evaluated under both air and vacuum conditions at elevated temperatures as well as after freeze-thaw cycles. Air-cured samples achieved sufficient hardening, whereas vacuum curing without prior outgassing produced porous structures and incomplete consolidation, highlighting the importance of controlling this process prior to curing. An ultimate com- pressive strength of 20.9 MPa was achieved in hardened samples after four days of curing and three days of freeze-thaw cycles. The hardening process was not negatively affected by freezing. The samples cured in air for 7 days achieved 24.16 MPa of compressive strength and 6.34 MPa of flexural strength. After further granulometric adjustments, printability via Cement Contour Crafting of simple geometries was evaluated. Overall, the results demonstrate that the developed low-water-content geopolymer is a promising candidate for lunar construction. It warrants further investigation into extrusion-based manufacturing and the mechanical and durability properties of hardened components.
La creazione di avamposti di superficie sicuri e duraturi rappresenta una sfida centrale per le future missioni lunari con equipaggio. L’utilizzo delle risorse in situ (ISRU) è una strategia cruciale per ridurre costi e complessità delle missioni, limitando la neces- sità di trasportare materiali dalla Terra e sfruttando la regolite per produrre materiali da costruzione come calcestruzzi e ceramiche per schermature e componenti strutturali. I geopolimeri sono promettenti leganti inorganici adatti alla costruzione lunare medi- ante produzione additiva. In questo studio, sono state sviluppate formulazioni a basso contenuto d’acqua attivando il simulante di regolite delle Highlands lunari (LHS-1) con soluzioni di idrossido di sodio. La frazione polverosa (LHS-1D) è stata impiegata come modificatore reologico per ottimizzare la lavorabilità. Le proprietà rilevanti per la stam- pabilità, caratterizzate mediante reometria rotazionale oscillatoria, hanno mostrato che le miscele LHS-D15-L34 e LHS-D20-L034 presentano valori di yield stress tra 1700 e 2500 Pa e viscosità paragonabili ai sistemi cementizi di riferimento, indicando compatibilità teorica con i processi di estrusione. Il comportamento di indurimento (curing) è stato valutato sia in aria che in condizioni di vuoto a temperature elevate, oltre che a seguito di cicli di gelo-disgelo. I campioni maturati in aria hanno raggiunto un indurimento sufficiente, mentre la maturazione in vuoto senza previo degasamento ha prodotto strut- ture porose e un consolidamento incompleto, evidenziando l’importanza del controllo di questo processo prima della fase di curing. Nei campioni induriti è stata raggiunta una resistenza a compressione ultima di 20,9 MPa dopo quattro giorni di maturazione ad alte temperature e tre giorni di cicli di gelo-disgelo. Il processo di indurimento non è stato influenzato negativamente dalle temperature di congelamento. I campioni induriti per 7 giorni in aria hanno raggiunto resistenza a compressione di 24.16 MPa e 6.34 MPa di resistenza flessionale. Complessivamente, i risultati dimostrano che il geopolimero a basso contenuto d’acqua sviluppato è un candidato promettente per la costruzione lunare. Lo studio suggerisce ulteriori indagini sulla produzione basata su estrusione e sulle proprietà meccaniche e di durabilità dei componenti induriti.
Developing low-binder lunar regolith geopolymers for construction on the Moon using cement contour crafting additive manufacturing
Di Mattia, Lorenzo
2024/2025
Abstract
The creation of secure and long-lasting surface outposts is a significant challenge for fu- ture crewed lunar missions. In-Situ Resource Utilization (ISRU) is a crucial strategy that can help lower mission costs and complexity by reducing the need to transport materials from Earth. Here, lunar regolith can be exploited to produce construction materials such as concrete and ceramics, enabling the fabrication of shielding structures, landing pads, and structural components. Geopolymers are a promising class of inorganic binders suit- able for lunar construction via additive manufacturing. In this study, low-water-content formulations were developed using aluminosilicate-rich lunar highlands regolith simulant activated with sodium hydroxide solutions. LHS-1-based mixtures were selected for de- tailed investigation due to their scientific relevance, with the dust fraction (LHS-1D) used as a rheological modifier to improve workability. Rheological properties relevant to printability and buildability were characterized by rotational rheometry under oscillatory conditions. The most promising formulations (LHS-D15-L34 and LHS-D20-L034) exhib- ited yield stress values between 1700 and 2500 Pa and viscosities comparable to reference cement systems, indicating compatibility with extrusion-based printing. Curing behaviour was evaluated under both air and vacuum conditions at elevated temperatures as well as after freeze-thaw cycles. Air-cured samples achieved sufficient hardening, whereas vacuum curing without prior outgassing produced porous structures and incomplete consolidation, highlighting the importance of controlling this process prior to curing. An ultimate com- pressive strength of 20.9 MPa was achieved in hardened samples after four days of curing and three days of freeze-thaw cycles. The hardening process was not negatively affected by freezing. The samples cured in air for 7 days achieved 24.16 MPa of compressive strength and 6.34 MPa of flexural strength. After further granulometric adjustments, printability via Cement Contour Crafting of simple geometries was evaluated. Overall, the results demonstrate that the developed low-water-content geopolymer is a promising candidate for lunar construction. It warrants further investigation into extrusion-based manufacturing and the mechanical and durability properties of hardened components.| File | Dimensione | Formato | |
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Master Thesis - Di Mattia.pdf
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Executive Summary - Di Mattia.pdf
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https://hdl.handle.net/10589/251267