Nonterrestrial Cements

T. D. Lin, of Construction Technology Laboratories (CTL), the research arm of the Portland Cement Association, proposed to our workshop group the manufacture of cement from lunar oxides and in his paper proposes concrete as a building material fora space station and a lunar base. The major constituents of common types of cement occur in lunar highland anorthosites and lunar mare basalts. The high compressive strength and the mass of lunar-derived concrete would make it an effective shield against radiation and micrometeorite impacts and thus a candidate material for orbital and lunar structures. Concrete is fireproof, lends itself to modular construction, and can be reinforced with Moon-derived metals and fiberglass to improve its tensional and flexural strength. Lunar cement would also be useful as mortar to assemblebuilding blocks of other materials, whether imported or nonterrestrial. Common concrete mixtures are about 10 percent water by weight, but drier formulations can be developed and the water can be recovered as the concrete dries. In any case, typical concretes, which consist of 2/3 to 3/4 aggregate materials bonded by cement, retain only 5 percent water when thoroughly dried, which corresponds to only a few tenths of a percent of Earth-derived mass in the form of hydrogen (Cullingford, Keller, and Higgins 1982). Suitable lut1ar aggregates could readily be obtained by crushing and grading rocks from the lunar surface.

I have proposed a method for concentrating lime (CaO) in lunar materials to Portland cement formula levels, using phosphates that might be lunar derived. A similar process was proposed by Ellis M. Gartner, of CTL, using terrestrial phosphate. Construction Technology Labs received 40 grams of lunar soil from the Johnson Space Center in 1986; from it CTL fabricated a lunar mortar sample, which was tested and proved usable. NASA is interested and the project has attracted favorable attention from the press. The apparent widespread interest in cement as a lunar product and public recognition of it may generate substantial support for its development.

The consensus of the group working on beneficiation and extraction of nonterrestrial materials was that there is a near-term need for bench-level data on lunar and meteoritic materials processing, such as (1) beneficiation of industrially valuable minerals in lunar soils and disaggregated lunar rocks and meteorites; (2) oxygen and metal extraction processes, like carbothermal reduction of silicates, hydrogen reduction of ilmenite, magma electrolysis, vacuum pyrolysis, and anhydrous chloride reduction, using actual nonterrestrial samples; and (3) formulation of cementitious compounds from lunar oxides and aggregates. The above research should be conducted under conditions approximating, as closely as practicable, the expected operating environment. This work is necessary to make a credible case for nonterrestrial materials utilization to the materials science community.

Recommendations

  1. Support for a thorough bench-level hardware investigation and demonstration of the beneficiation, primarily by electrostatic and magnetic means, of lunar soils and crushed rocks for minerals like ilmenite, anorthite, and pyroxenes, and valuable minor phases like metal, chromite, and phosphate.
  2. Support for bench-level research and development of the carbothermal process, including additional testing to determine optimum pressure and temperature conditions for feedstocks of various compositions, such as simulated mare basalt and concentrates of ilmenite or pyroxene.
  3. Support for a thorough investigation of the thermodynamics and kinetics of hydrogen reduction of lunar ilmenite, together with a bench- level laboratory research project to investigate the workability of hardware designs like those of Richard J. Williams and Christian W. Knudsen and Michael A. Gibson.
  4. Support for additional studies of magma electrolysis, including laboratory work on the basic process, development of innovative electrodes and containers, and investigation of the effects of feedstock of different compositions. This effort should also include engineering evaluations and plant design concepts.
  5. Support for a thorough investigation of the thermodynamics and kinetics of solar furnace vacuum pyrolysis of nonterrestrial materials. The effort shouldinclude a bench-level research project to characterize, quantity, separate, and capture oxygen and other volatiles liberated by high- temperature vacuum pyrolysis of lunar and meteoritic materials, as well as thorough characterization and chemical analysis of resulting condensates and residues.
  6. A literature search and evaluation of the anhydrous chloride process for plutonium reclamation reported by David F. Bowersox and its applicability to production of metals and ceramics from nonterrestrial materials.
  7. Support for bench-level research on aqueous leaching of nonterrestrial silicates with inorganic acids like hydrofluoric acjd, as well as beneficiation by bioprocesses derived from the action of microorganisms on nonterrestrial minerals.
  8. A study of the application of the carbonyl process to the purification and extraction of lunar and asteroidal ferrous metals.
  9. Support for the development of cement formulations from lunar materials and cement and concrete fabrication processes adapted to lunar and orbital manufacture and applications.

References

Agosto, W. N., and E. A. King. 1983. In Situ Solar Furnace Production of Oxygen, Metals and Ceramics From Lunar Materials. In Lunar & Planetary Sci. XIV, Special Session Abstracts: Return to the Moon (March 16) and Future Lunar Program (March 17), pp. 1-2. Houston: Lunar & Planetary Inst.

Agosto, William N. 1981. Beneficiation and Powder Metallurgical Processing of .Lunar Soil Metal. In Space Manufacturing 4, Proc. 5th Princeton/AIAA Conf., ed. Jerry Grey and Lawrence A. Hamdan, 365-370. New York: AIAA.

Criswell, David R. 1980. Extraterrestrial Materials Processing and Construction. Final Report on Mod. No. 24 of NASA contract NSR 09-051-001.. Houston: Lunar & Planetary Inst.

Cullingford, H. S.; M. D. Keller, and R. W. Higgins. 1982. Compressive Strength and Outgassing Characteristics of Concrete for Large Vacuum- System Construction. J. Vac. Sci. Technol.20:1043-1047.

King, Elbert A. 1982. Refractory Residues, Condensates and Chondrules From Solar Furnace Experiments. Proc. 13th Lunar & Planetary Sci. Cont, Part 1. J. Geophys. Res. 87 (suppl.): A429- A434.

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