Utilization of urea as an accessible superplasticizer on the moon for lunar geopolymer mixtures
Open accessAbstract
When developing materials for lunar construction, it is essential to minimize the weight of components that have to be brought in from Earth. All necessary ingredients for geopolymers could potentially be sourced on the lunar surface, which is why the material might be an efficient construction material for infrastructure on the moon. Finding a chemical admixture that can be easily obtained on the moon, which can increase the workability while utilizing less water, would be highly beneficial for utilizing lunar regolith geopolymers for lunar 3D printing. Urea can break hydrogen bonds, and therefore reduces the viscosities of many aqueous mixtures. Since urea is the second most abundant component in urine (after water), it is readily available anywhere there are humans. We have therefore explored the possibility of utilizing urea as a chemical admixture for lunar geopolymers. Addition of urea has been compared with polycarboxylate and naphthalene based superplasticizers, and with a control mixture without superplasticizer. When curing the sample containing urea at 80 °C, the initial setting time became longer. The samples containing urea or naphthalene-based superplasticizers could bear heavy weights shortly after mixing, while keeping an almost stable shape. Samples without superplasticizer or containing the polycarboxylate-based admixture were too stiff for mold-shaped formation after casting. Samples containing urea and naphthalene-based admixtures could be used to build up a structure without any noticeable deformation. Initial compressive strength of the samples with urea was higher than for the two other specimens containing superplasticizers, and it continued to rise even after 8 freeze-thaw cycles. Microstructural studies revealed that superplasticizers can influence the formation of additional air voids within the samples.
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The compressive strength of geopolymer increases by a factor of 6 or more when exposed to a thermal cycle of −80~114 °C in air and vacuum.
“The compressive strength of geopolymer was found to increase by a factor of 6 or more when exposed to a thermal cycle of −80~114 °C in air and vacuum.”
From A Review on Geopolymer Technology for Lunar Base Construction (2022) · cites this paper as [21]
Section 3.3 (page unavailable) reports an overall strength increase over eight freeze–thaw cycles for three sample types, but only a slight increase for the urea sample; it does not report a sixfold increase. Section 2.2 (page unavailable) specifies cycles between −80 °C and 80 °C, not 114 °C, and the cited passages do not establish results in both air and vacuum. (LLM, conf=0.88)
Experimental — accuracy not yet measuredNo further studies have been conducted in Pilehvar et al.'s work to assess how this Lunar regolith geopolymer behaves in a Lunar setting.
“However, no further studies have been conducted in their work to assess how this Lunar regolith geopolymer behaves in a Lunar setting.”
From A comprehensive review of lunar-based manufacturing and construction (2024) · cites this paper as [275]
The Conclusions say further studies are needed to assess behavior under severe lunar conditions, including vacuum and large temperature fluctuations. But Methods §2.2 and Results §3.3 report freeze–thaw tests and compressive-strength measurements, so the paper did assess one aspect of behavior relevant to a lunar setting. It did not test the geopolymers under full lunar conditions. (LLM, conf=0.84)
Experimental — accuracy not yet measuredAs-printed specimens displayed an initial compressive strength of 13 MPa.
“The as-printed specimens displayed an initial compressive strength of 13 MPa .”
From A comprehensive review of lunar-based manufacturing and construction (2024) · cites this paper as [275]
Section 3.3 reports an initial compressive strength of 13 MPa for the urea-containing (U) sample after precuring at 80 °C. But Section 2.2 says the specimens were cast into molds, not printed; the paper describes the result as relevant to 3D printing rather than a measurement of as-printed specimens. Page numbers are unavailable in our copy. (LLM, conf=0.90)
Experimental — accuracy not yet measuredThe compressive strength of geopolymers increases when repeatedly exposed to low-high-temperature cycles similar to those on the lunar surface.
“Pilehvar et al. (2020, 2021) found that when conducting durability tests, the compressive strength of geopolymers increased when repeatedly exposed to a low–high-temperature cycle similar to that experienced on the lunar surface [21,51].”
From A Review on Geopolymer Technology for Lunar Base Construction (2022) · cites this paper as [21]
Workability and buildability tests showed an alkaline solution-to-regolith ratio of 0.35:1 and a urea dosage of 3% of Lunar regolith mass was optimal.
“Workability and buildability tests showed an alkaline solution-to-regolith ratio of 0.35:1, and a urea dosage corresponding to 3 % of the Lunar regolith mass was optimal.”
From A comprehensive review of lunar-based manufacturing and construction (2024) · cites this paper as [275]
The mixture could be pumped to build objects layer by layer with good flowability and retain its shape under external loads.
“The mixture could be pumped to build objects layer by layer with good flowability and retain its shape under external loads.”
From A comprehensive review of lunar-based manufacturing and construction (2024) · cites this paper as [275]
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References 42 · Cited by 139
Research works printed but not linked: 2
- Ceccanti, F., Dini, E., De Kestelier, X., Colla, V., Pambaguian, L., 2010. In: 3D Printing Technology for a Moon Outpost Exploiting Lunar Soil, 61st International Astronautical Congress, pp. 1e9. Prague, CZ, IAC-10-D3.
- McKay, D.S., Heiken, G., Basu, A., Blanford, G., Simon, S., Reedy, R., French, B.M., Papike, J., 1991. The Lunar Regolith, Lunar Sourcebook. Camebridge University Press, Houston, Texas.
- Authors
- Pilehvar, S., Arnhof, M., Pamies, R., Valentini, L., & Kjøniksen, A.-L.
- Affiliations
- Østfold University of Applied Sciences (NO)
- European Space Agency (FR)
- Universidad Politécnica de Cartagena (ES)
- University of Padua (IT)
- Corresponding author
- Kjøniksen, Anna-Lena
- Venue
- Journal of Cleaner Production
- Publisher
- Elsevier BV
- Published
- 2020-02
- Volume
- 247
- Pages
- 119177
- ISSN
- 0959-6526 (ISSN-L)
- OpenAlex
- W2983207286
- Cited by
- 139
- References
- 42
- Citations by year
- 2026: 18 · 2025: 29 · 2024: 35 · 2023: 19 · 2022: 20 · 2021: 11 · 2020: 7
- FWCI
- 6.37
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- Locations
- Journal of Cleaner Production (publishedVersion, cc-by-nc-nd)
- Padua Research Archive (University of Padova) (submittedVersion, cc-by-nc-nd)
- NORA - Norwegian Open Research Archives (submittedVersion, cc-by-nc-nd)
- INFM-OAR (INFN Catania) (submittedVersion, cc-by-nc-nd)
- Funders
- Fundación Séneca Agencia de Ciencia y Tecnología de la Región de Murcia (19877/GERM/14)
- Topics
- Physical Sciences › Engineering › Building and Construction › Innovations in Concrete and Construction Materials
- Physical Sciences › Engineering › Civil and Structural Engineering › Concrete and Cement Materials Research
- Physical Sciences › Environmental Science › Environmental Engineering › Microbial Applications in Construction Materials
- Keywords
- urea, superplasticizer, lunar regolith, lunar construction, chemical admixtures, naphthalene superplasticizer, polycarboxylate superplasticizer, setting time, compressive strength, freeze-thaw resistance, air voids, microstructure, hydrogen bond breaking, low water content
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