International Concrete Abstracts Portal

The methodology for forming and placing lunar concretes will incorporate our present technology as well as add the innovations that will be developed in the years to come. Initial habitation will combine the use of inflatable forms, precast modules, and self-contained modules that are landed on the lunar surface. The forming and placing systems used for cast-in-place lunar concrete may include temporary stay-forms, preplaced aggregate concrete (which utilizes injection grouting), air-o-form system, and precast concrete. Lightweight fiberglass formties have great potential for lunar construction. A case history and discussion for preplaced aggregate concrete usage is provided for the Peoria Lock Resurfacing Project. The placement size was 1 ft (0.3048 m) wide x 40 ft (12.2 m) long x 10 ft (3.1 m) deep. The maximum size aggregate was 3 in. (7.6 cm) for increased economy. Typically, the angle of repose for the grout was 1:10. Test results for 7-day and 28-day compressive strengths for 2 in. (5 cm) mortar cubes, preplaced aggregate concrete cylinders, and conventional concrete are given. Other items discussed in the article are concretes for a lunar landing support facility, modified shotcreting and curing methods, and a variety of modified inflatable form structures.

Concrete-like materials can be envisioned for applications in the construction of a lunar base in the next century. Although the technology for the manufacture and use of such materials on the moon is not yet available, many people have begun to investigate the possibilities for applications of cements and concretes adapted to the lunar environment. It will be essential that enabling technologies and processes for lunar concrete be developed and proven to have a high degree of reliability. Equipment and operational procedures must then be thoroughly tested under realistic conditions before commitment to lunar base construction. The authors believe that a need exists for a major center of knowledge and education with a simulation facility, where the technologies for lunar and Mars operations can be verified for effectiveness and suitability, to preclude costly surprises and breakdowns in extraterrestrial operations. The authors are planning a Center for Extraterrestrial Engineering and Construction (CETEC), which will serve such a purpose. The CETEC group encompasses many people from across the nation representing national laboratories, universities, constructors, aerospace firms, research and development companies, government, and small business. CETEC will give developers of lunar concrete access to necessary expertise and test facilities to achieve the goals of the space exploration initiative. At CETEC, simulated materials of the moon and Mars will be available in vacuumin appropriate hot and cold dusty environments, so that concepts and prototype equipment for cement and concrete production and use can be verified on a large enough scale to satisfy skeptics and advance all uses of in situ lunar materials for the benefit of humankind.

Effects of a vacuum environment on properties of hardened mortar made with cement-based materials are discussed. In this study, mortar specimens were exposed to a vacuum environment after various water curing periods. Several characteristics of the specimens, such as weight, strain, porosity, and strength, were measured before and after the vacuum exposure. A significant water loss and shrinkage strain were observed in tested specimens after specific vacuum exposure. Therefore, some measures are required to prevent shrinkage-induced cracks. In some cases, strengths for some vacuum-exposed mortar specimens were higher than water-cured companion specimens. Based on these experimental results, possible applications of concrete on the moon are recommended in this study.

This paper suggests establishing the applicability and manufacturing technique of GFRP, particularly dimethylisophtalate glass-filament rod. The use of GFRP reinforcement in lieu of conventional steel rods and wires has great potential for precast structural concrete elements. GFRP may be cheaper, lighter, and formed from materials found in abundance on earth and on the moon, namely silica (SiO2). GFRP can be manufactured with the same, if not higher, tensile properties of steel. If synergically composed with a plastic carrier, a new science in construction and structural analysis could be born. No doubt remains that lunar soil is cementitious. Rocks for aggregate and silica are also abundant on the moon. Heavy fabricated steel rods are counterproductive for transport to the moon. Glass fibers fabricated on the moon have great potential. Permanent settlement/habitats on the moon are within the realm of possibility and may be considered immediate projects. Therefore, the idea of using local materials is appropriate within the concept of a third phase of permanent underground reinforced concrete construction facilities, the first being the Apollo landings and the second a temporary above-ground lunar establishment yet to come. This analysis could lend itself not only to permanent reinforced concrete structures on the moon, but to any other planet where silica is abundant and cement could become a local product, through refining and reducing appropriate local ores. Manufacture of glass-fiber filaments is incomparably cheaper than steel. Additional research, at a later date, will encompass the application of pre- and post-tensioned GFRP reinforcements, using the same structural form elements. This paper proves the positive applicability of GFRP as reinforcement for precast concrete elements.

An important aspect of lunar concrete production will be the production of lime (CaO) from lunar rocks. Chemical and thermodynamic data show that lime could most easily be distracted from abundant lunar anorthite (CaAl2Si2O8) the major mineral in the anorthositic lunar highlands. If fluorine gas, produced on site by electrolysis of molten NaF, is used as the extracting agent, oxygen, silicon, and aluminum can be recovered at the same time. Of these, oxygen is likely to be the most valuable product. Lime is recovered from fluorite, CaF2, by reaction with soda, Na2O; the resulting NaF is recycled into fluorine production immediately before use. No fluorine gas is transported or stored in this process; it is used up as soon as it is made.