Based on the available data on abundance and composition of lunar materials, lunar basalts were selected as a prospective base source for cement production. Methods of increasing calcium content of natural raw materials were developed. The experimental study was conducted in two directions: sintering mixes of natural materials with CaO and activating mineral glasses obtained by beneficiation of the natural rocks. In both cases, the terrestrial materials were selected to simulate the lunar rocks. The sintered cement exhibited properties analogous to those of known portland cements. The vitreous material simulating the composition of beneficiated lunar rocks developed cementitious properties when it was activated by the chemical agent and cured under the conditions of high humidity and elevated temperatures.

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.

In the lunar environment, the use of solar thermal energy has obvious advantages over any combustion or electrical furnace for driving high-temperature processes. However, extremely high temperatures, in the range of 1700 to 2000 C, will be necessary to produce cement from lunar minerals and will, in turn, require very high levels of solar flux concentration. Such levels can only be achieved in practice with some form of ideal or near-ideal nonimaging concentrator that can approach the maximum concentration permitted by physical conservation laws. In particular, very substantial gains in efficiency can be generated through the incorporation of a properly designed ideal or near-ideal nonimaging secondary concentrator in a two-stage configuration with a long focal ratio primary concentrator. A preliminary design configuration for such a high-flux nonimaging solar concentrating furnace for lunar applications is presented. It employs a tracking heliostat and a fixed, off-axis, two-stage concentrator with a long focal length utilizing a nonimaging trumpet or CPC-type secondary deployed in the focal zone of the primary. An analysis of the benefits associated with this configuration employed as a solar furnace in the lunar environment shows that the thermal conversion efficiency can be about 3 to 5 times that of the corresponding conventional design at 2000 C. Furthermore, this configuration allows the primary collecting aperture to remain unshaded by the furnace or any associated support structure.

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.

In July 1989, those who advocate U.S. space programs received a significant boost from President Bush's declaration that the U.S. should return to the moon (this time to stay) and then go on to Mars. Achieving these objectives will thrust engineers of ma