spore: profile
id: geopolymer-lunar-concrete
spore_version: 0.2
family: geopolymer
name: Geopolymer lunar concrete (alkali-activated regolith)
role: Binder that sets lunar regolith simulant with an alkaline solution instead of Portland cement
category: regolith
type: lunar-concrete
status: draft
author: assistant
summary: Geopolymer lunar concrete is a binder that sets lunar regolith simulant with an alkaline solution of sodium silicate and sodium hydroxide, in place of Portland cement. NASA's 2022 Earth Day deck concludes that geopolymer concrete is a feasible material for lunar surface infrastructure, and it tabulates the amorphous content, Si/Al ratio and particle size of five regolith simulants. The sources read for this profile print no compressive strength value, and the 2022 conference abstract reports a noticeable decline in strength when curing is done at reduced pressure.
best_for: Concept studies of lunar construction that use regolith as found, with an activator the 2022 abstract says could largely be produced in situ (laboratory stage only)
weakest_at: No strength value is printed in any source read; strength falls when curing pressure is reduced, and no flight or vacuum test values were found
identity:
  formula: 'Alkali-activated aluminosilicate binder (geopolymer): lunar regolith simulant activated by sodium silicate and sodium hydroxide; no single formula'
  source: nasa-deck-2022
  where: Slide 8 (aluminosilicate glassy sources and alkaline solution); Slide 9 (geopolymer definition cites Duxson et al. 2007)
tags:
  environments: []
  stresses: []
  applications:
    - structures
    - habitats-and-suits
properties:
  - benchmark: amorphous_content
    label: Amorphous content, JSC-1A lunar mare simulant
    value: 49.9
    unit: '%'
    scope: material
    conditions:
      simulant: JSC-1A, lunar mare regolith simulant
      form: as tabulated in the deck
    method: XRD phase table on the slide; the slide does not state how the amorphous fraction was quantified
    status: ground
    source: nasa-deck-2022
    where: Slide 18, Amorphous column, JSC-1A row
  - benchmark: amorphous_content
    label: Amorphous content, JSC-2A lunar mare simulant
    value: 51
    unit: '%'
    scope: material
    conditions:
      simulant: JSC-2A, lunar mare regolith simulant
      form: as tabulated in the deck
    method: XRD phase table on the slide; the slide does not state how the amorphous fraction was quantified
    status: ground
    source: nasa-deck-2022
    where: Slide 18, Amorphous column, JSC-2A row
  - benchmark: amorphous_content
    label: Amorphous content, OPRL2N lunar mare simulant
    value: 45.4
    unit: '%'
    scope: material
    conditions:
      simulant: OPRL2N, lunar mare regolith simulant
      form: as tabulated in the deck
    method: XRD phase table on the slide; the slide does not state how the amorphous fraction was quantified
    status: ground
    source: nasa-deck-2022
    where: Slide 18, Amorphous column, OPRL2N row
  - benchmark: amorphous_content
    label: Amorphous content, OPRH2N lunar highlands simulant
    value: 26.5
    unit: '%'
    scope: material
    conditions:
      simulant: OPRH2N, lunar highlands regolith simulant
      form: as tabulated in the deck
    method: XRD phase table on the slide; the slide does not state how the amorphous fraction was quantified
    status: ground
    source: nasa-deck-2022
    where: Slide 18, Amorphous column, OPRH2N row
  - benchmark: amorphous_content
    label: Amorphous content, EAC-1A lunar simulant
    value: 26.2
    unit: '%'
    scope: material
    conditions:
      simulant: EAC-1A, lunar regolith simulant
      form: as tabulated in the deck
    method: XRD phase table on the slide; the slide does not state how the amorphous fraction was quantified
    status: ground
    source: nasa-deck-2022
    where: Slide 18, Amorphous column, EAC-1A row
  - benchmark: si_al_ratio
    label: Si/Al ratio, JSC-1A simulant
    value: 2.5
    unit: '-'
    scope: material
    conditions:
      simulant: JSC-1A
      basis: oxide composition as tabulated
    method: Printed Si/Al column of the oxide table; the table gives SiO2 and Al2O3 without units, so only the ratio is recorded
    status: ground
    source: nasa-deck-2022
    where: Slide 19, Si/Al column, JSC-1A row
  - benchmark: si_al_ratio
    label: Si/Al ratio, OPRL2N lunar mare simulant
    value: 2.44
    unit: '-'
    scope: material
    conditions:
      simulant: OPRL2N
      basis: oxide composition as tabulated
    method: Printed Si/Al column of the oxide table; the table gives SiO2 and Al2O3 without units, so only the ratio is recorded
    status: ground
    source: nasa-deck-2022
    where: Slide 19, Si/Al column, OPRL2N row
  - benchmark: si_al_ratio
    label: Si/Al ratio, OPRH2N lunar highlands simulant
    value: 1.63
    unit: '-'
    scope: material
    conditions:
      simulant: OPRH2N
      basis: oxide composition as tabulated
    method: Printed Si/Al column of the oxide table; the table gives SiO2 and Al2O3 without units, so only the ratio is recorded
    status: ground
    source: nasa-deck-2022
    where: Slide 19, Si/Al column, OPRH2N row
  - benchmark: particle_size_d50
    label: Median particle size (D50), OPRL2N lunar mare simulant
    value: 58
    unit: µm
    scope: material
    conditions:
      simulant: OPRL2N
      measurement: laser particle size distribution, as named in the deck
    method: Printed D50 column of the particle size table on the slide
    status: ground
    source: nasa-deck-2022
    where: Slide 19, D50 (µm) column, OPRL2N row
  - benchmark: particle_size_d50
    label: Median particle size (D50), OPRH2N lunar highlands simulant
    value: 46.2
    unit: µm
    scope: material
    conditions:
      simulant: OPRH2N
      measurement: laser particle size distribution, as named in the deck
    method: Printed D50 column of the particle size table on the slide
    status: ground
    source: nasa-deck-2022
    where: Slide 19, D50 (µm) column, OPRH2N row
  - benchmark: activator_ph
    label: pH of the reference alkaline activator
    value: 14.31
    unit: '-'
    scope: material
    conditions:
      activator: sodium silicate and 10 M sodium hydroxide mixture
      silicate_ratio_SiO2_Na2O: 2
      solution_to_simulant: 0.35
    method: Printed on the mix footnote of the slide with the compressive strength chart; the slide gives no measurement method
    status: ground
    note: The pH is a property of the activator solution, not of the hardened concrete.
    source: nasa-deck-2022
    where: Slide 21, mix footnote
  - benchmark: sio2_na2o_ratio
    label: SiO2/Na2O ratio of the sodium silicate in the reference mix
    value: 2
    unit: '-'
    scope: material
    conditions:
      activator: sodium silicate with 10 M sodium hydroxide
    method: Printed on the mix footnote of the slide with the compressive strength chart
    status: ground
    source: nasa-deck-2022
    where: Slide 21, mix footnote
  - benchmark: solution_to_solid_ratio
    label: Solution to simulant ratio in the reference mix
    value: 0.35
    unit: '-'
    scope: material
    conditions:
      simulant: lunar regolith simulant (type not specified on the slide)
    method: Printed on the mix footnote of the slide with the compressive strength chart
    status: ground
    note: The slide does not say whether the ratio is by mass or by volume, so no unit is assumed.
    source: nasa-deck-2022
    where: Slide 21, mix footnote
  - benchmark: curing_temperature
    label: Reference mix cure temperature (process condition, not a material property)
    value: 80
    unit: °C
    scope: material
    conditions:
      cure_time: three days, as printed on the slide
      mix: reference geopolymer mix on the slide
    method: Printed cure condition on the mix footnote of the slide with the compressive strength chart
    status: ground
    source: nasa-deck-2022
    where: Slide 21, mix footnote (Cured at 80°C for three days)
corrosion:
  - environment: Vacuum exposure after curing (lunar surface condition)
    headline: Vacuum exposure limited further reaction and strength gain, compared with controls kept in the laboratory (qualitative)
    effect: Samples cured for different lengths of time were placed in a vacuum chamber, and their weight change and compressive strength were tracked against laboratory-stored controls. The 2022 abstract says exposure to the vacuum limits further reaction and strength gain. No numerical degradation values are printed in the abstract.
    rating: unknown
    conditions:
      exposure: vacuum chamber, pressure as stated in the abstract
      materials: geopolymer lunar concrete from the two regolith simulants OPRL2N and OPRH2N
    source: ntrs-2022-13413
    where: Abstract
risks:
  hazards: []
  failure_risks:
    - mode: Lower strength after curing at reduced pressure
      trigger: Curing at reduced pressure in a vacuum chamber
      consequence: The 2022 abstract reports a noticeable decline in strength with a reduction in pressure, and says vacuum exposure limits further reaction and strength gain.
      severity: moderate
      source: ntrs-2022-13413
      where: Abstract
  side_effects: []
  handling:
    - text: The 2022 abstract says printed lunar infrastructure would need a temporary environmental enclosure during construction and curing, and that data are needed to set benchmark enclosure conditions.
      source: ntrs-2022-13413
      where: Abstract
  mitigations: []
uses:
  - application: structures
    device: Lunar habitats, roads and landing pads (concept)
    example: The 2022 conference abstract proposes geopolymer concrete for lunar habitats, roads and landing pads, made from regolith as found mixed with sodium silicate and sodium hydroxide.
    source: ntrs-2022-13413
    where: Abstract
  - application: structures
    device: Lunar surface infrastructure (concept)
    example: The Earth Day 2022 deck concludes that geopolymer concrete is a feasible material for constructing infrastructure on the lunar surface.
    source: nasa-deck-2022
    where: Slide 22, Conclusions
supply: []
media: []
documents:
  - title: 'Geopolymer Concrete: A greener alternative on Earth and a feasible material for the Moon (Earth Day 2022 presentation, NTRS 20220005876)'
    type: report
    url: https://ntrs.nasa.gov/api/citations/20220005876/downloads/Earth%20Day%202022%20Geopolymer%20Concrete.pdf
    year: 2022
  - title: Geopolymer Lunar Concrete under Reduced-Pressure Curing and Vacuum Exposure (NTRS 20220013413, IAC 2022 conference paper)
    type: paper
    url: https://ntrs.nasa.gov/citations/20220013413
    year: 2022
gaps:
  - No compressive strength, flexural strength or density value is printed in any source read in this run. The strength chart on slide 21 plots two simulant mixes against age, but it prints no data values, so none are recorded.
  - Hazard data for the sodium hydroxide and sodium silicate activators were not found. The PubChem pages returned a browser verification check, so risks.hazards is empty.
  - No producer, abundance or critical-mineral data are recorded. The Earth Day deck credits PQ Corporation for providing the sodium silicate, but gives no production shares or country data, so supply is empty.
  - The 'tested on the ISS' claim in the profile brief was not found in the two NASA documents read. The deck acknowledges a microgravity cement solidification project, but names no ISS test result.
  - The 2022 conference paper was read from its NTRS citation page through a summarising fetch. Its PDF link returned an error, so its quoted phrases were not checked word for word against the paper.
  - The simulant SiO2 and Al2O3 values on slide 19 have no units printed in the table, so they are not recorded. Only the printed Si/Al ratios are kept.
  - The pH, SiO2/Na2O ratio, solution-to-simulant ratio and 80 C cure come from one mix footnote on slide 21. The slide gives no measurement method beyond the mix description.
  - Environment figures on slide 14 (gravity, temperature range, and an atmospheric pressure printed with an exponent) describe the lunar surface, not the material, and are left out.
  - Benchmarks amorphous_content, si_al_ratio, particle_size_d50, activator_ph, sio2_na2o_ratio, solution_to_solid_ratio and curing_temperature are not in spores/property-canon.yaml and are used as snake_case names.
  - Only three sources are cited, below the eight required for the full-grade bar. There is no ageing, durability, radiation or flight data and no corrosion test beyond the vacuum statement.
  - Wikipedia (Geopolymer) was read for the definition and history of the term but yielded no lunar or grade-specific numbers, so it is not cited as a value source.
sources:
  nasa-deck-2022:
    title: 'Geopolymer Concrete: A greener alternative on Earth and a feasible material for the Moon (Earth Day 2022 presentation)'
    id: NTRS 20220005876; authors Collins, Radlinska, Edmunson, Fiske, Strutzenberg
    url: https://ntrs.nasa.gov/api/citations/20220005876/downloads/Earth%20Day%202022%20Geopolymer%20Concrete.pdf
    year: 2022
    kind: report
    license: Not stated on the slides
  ntrs-2022-13413:
    title: Geopolymer Lunar Concrete under Reduced-Pressure Curing and Vacuum Exposure
    id: NTRS 20220013413; IAC 2022 conference paper (Collins, Edmunson, Fiske, Bilen, Radlinska)
    url: https://ntrs.nasa.gov/citations/20220013413
    year: 2022
    kind: paper
    license: Not stated on the citation page
  wikipedia-geopolymer:
    title: Geopolymer (Wikipedia article)
    id: en.wikipedia.org, Geopolymer
    url: https://en.wikipedia.org/wiki/Geopolymer
    year: 2026
    kind: web
    license: CC BY-SA (Wikipedia text)
story:
  recipe:
    line: Geopolymer lunar concrete is made by mixing a glassy aluminosilicate powder, here lunar regolith simulant, with an alkaline solution. The reference mix on slide 21 uses a sodium silicate and 10 M sodium hydroxide solution, and it is cured at 80°C for three days.
    parts:
      - name: Lunar regolith simulant
        role: Aluminosilicate source. Its amorphous (glassy) content runs from 26.2% to 49.9% across the five simulants on slide 18, and the glassy part is what reacts with the activator.
      - name: Sodium silicate
        role: Part of the alkaline solution. The reference mix sets its SiO2/Na2O ratio, recorded in the properties from slide 21. PQ Corporation supplied the sodium silicate, according to the deck's acknowledgements.
      - name: Sodium hydroxide
        role: Part of the alkaline solution, at a concentration of 10 M in the reference mix (slide 21).
  risk_groups:
    - title: For people
      level: 0
      verdict: Hazard data not found in this run
      lead: No hazard classification for the activators was read in this run, so this profile does not state one.
      points:
        - label: Activators
          line: The sodium hydroxide and sodium silicate in the mix were not checked against a safety data sheet or a chemical database entry here. Treat the alkaline solution as a chemical that needs its own safety data sheet before handling.
        - label: Dust
          line: The sources read here do not discuss dust from regolith simulant, so no dust guidance is given.
    - title: Handling in construction concepts
      lead: These points come from the 2022 conference abstract, which describes a concept, not a built structure.
      points:
        - label: Curing enclosure
          line: Printed lunar infrastructure would need a temporary environmental enclosure during construction and curing. The abstract says the benchmark enclosure conditions still need data.
        - label: Reduced pressure
          line: The abstract reports a noticeable decline in strength when curing is done at reduced pressure.
  why: Geopolymer lunar concrete is proposed as a binder for lunar construction that does not rely on Portland cement. NASA's deck says the calcium content of lunar regolith is minimal for making ordinary Portland cement, and it proposes regolith in its as-is condition as the main mass of the mix. The work so far has used regolith simulants, not returned lunar samples, and the deck notes that no simulant is a perfect match for real lunar regolith.
  uses:
    - where: Lunar habitats, roads and landing pads (concept)
      line: The 2022 conference abstract proposes geopolymer concrete for these uses, with regolith used as found and mixed with sodium silicate and sodium hydroxide.
    - where: Lunar surface infrastructure
      line: The Earth Day 2022 deck concludes that geopolymer concrete is a feasible material for constructing infrastructure on the lunar surface.
  can_do:
    - label: Uses lunar regolith as found
      line: The deck states the goal is to use as much in-situ lunar resources as possible, with regolith in its as-is condition making up most of the mass.
    - label: Amorphous feedstock
      benchmark: amorphous_content
      line: The deck's table gives amorphous content from 26.2% (EAC-1A) to 49.9% (JSC-1A) across the five simulants (slide 18). It notes that the mare simulants have a higher amorphous content than most Apollo samples.
    - label: Alkaline activation
      benchmark: activator_ph
      line: The reference activator mixture has a pH of 14.31 (slide 21).
    - label: Curing
      benchmark: curing_temperature
      line: The reference mix is cured at 80°C for three days (slide 21). The 2022 abstract reports a noticeable decline in strength when curing pressure is reduced.
  compare: The deck lists geopolymer concrete among ways to reduce concrete's CO2 emissions, and it says geopolymers will not replace Portland cement across the board. Against Portland cement, the sources read here give no strength or durability numbers to compare, so the comparison rests on mix chemistry and on the reference mix conditions only. The table compares the feedstock and activator values this profile records.
  compare_rows:
    - label: Amorphous content of the feedstock (26.2% to 49.9%)
      benchmark: amorphous_content
    - label: Activator pH (reference mix)
      benchmark: activator_ph
    - label: Median particle size, OPRL2N (D50)
      benchmark: particle_size_d50
  handling:
    - Printed lunar infrastructure would need a temporary environmental enclosure during construction and curing, according to the 2022 abstract.
    - Use lunar regolith simulants for laboratory work. The deck says no simulant is a perfect match for real lunar regolith.
    - Curing at reduced pressure lowers strength, so curing conditions should be held constant when comparing mixes.
  good_for:
    - Concept studies that use regolith as found and an activator that the 2022 abstract says could largely be produced in situ.
    - Laboratory comparisons of regolith simulants, since the deck measures five simulants side by side.
  watch_out:
    - No strength value is printed in any source read, and strength falls when curing is done at reduced pressure.
    - Simulant only. The deck says no lunar regolith simulant is a perfect match for real lunar regolith.
    - Mix and activator values come from one footnote in the deck, with no measurement method beyond the mix description.
  verdict: A feasible concept according to NASA's own deck, supported so far by simulant chemistry and mix conditions only. No strength number was recorded, so the verdict does not rest on strength.