International Concrete Abstracts Portal

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.

The United States Air Force Academy's Engineering 410 class, Spring 1989, tested the feasibility of using concrete as a lunar construction material. This was a continuation of two previous semesters' effort. Concrete specimens were tested by combining different cement types, mixing environments, and additives to determine their effects on strengths and other engineering properties of the specimens. Using 5 different variables, a total of 80 possible combinations existed. The group used a D-optimal design with 18 possible combinations to build a prediction equation to optimize the concrete design mixture. Confirmation tests were conducted on the optimal design and compared with the mathematical algorithm prediction. The results demonstrate the power of this approach in experimentation for concrete applications.

Lunar base concepts utilizing concrete as structural material have been proposed recently. These are based on the consideration that oxygen and raw materials used in manufacturing cement will be extracted from lunar resources and that the soils and rocks will be used as aggregates of concrete. The moon has an abundance of raw material used in manufacturing cement within its rocky soil, thus requiring rocks to be crushed. The paper discusses a unique rock-breaking system using plentiful solar energy available on the moon: that is, sudden heating of a rock surface induces high thermal stress within the rock, which results in the rock breaking. Appropriate heat flow and radiating time are calculated using the physical property of basalt, which has a similar chemical composition to lunar rock. Additionally, required system volume is estimated.

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.

Provides an overview of engineering studies performed in support of the Space Exploration Institute (SEI). Topics addressed include background on the SEI, lunar construction phases, lunar habitats, lunar oxygen, mechanical concepts, and lunar power. Although the topics do not relate equally to concrete construction, they do identify selected issues that must be addressed before a lunar outpost can evolve to the emplacement and operation phases. In these phases of lunar outpost development, maximum use will be made of native materials, such as lunar concrete.