International Concrete Abstracts Portal

Lunar Concrete is the exciting new symposium volume which explores the production and use of concrete on the moon. Contained within 20 technical papers from well-known authorities on lunar concrete are details on lunar base construction, use of lunar resources, lunar concrete formulation, forming and placing lunar concrete, reinforcing lunar concrete, and environmental effects of lunar concrete, optimizing lunar concrete and much more. It may at first seem outrageous that concrete could be considered as primary material of construction for use on the Moon. However, a small group of scientists and engineers, many of them represented in this collection of papers, have persevered in examining this outrageous premise. Most, perhaps all, of the materials needed to make concrete are naturally present on the lunar surface. Although they have to be extracted and transformed, the energy required to do that, and probably the cost, is much less than that which would be required to bring the same quantity of material from the Earth to use on the Moon. The technology for utilizing these natural materials of the Moon would appear to be straightforward modifications of techniques that have been developed for terrestrial applications. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP125

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.

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.

The quality of concrete construction conventionally relies on the workability and consolidation of the concrete mixture. Practically speaking, the higher the amount of water used, the better the workability of fresh concrete; however, the use of excessive amounts of water will induce some detrimental effects on the quality of concrete. For example, the increase of water content in concrete mix proportions may reduce the bonding strength between cement paste and aggregate interface because of the voids and possibility of bleeding. To deal with this problem, compaction technology is adopted to produce precasted segments. A specific dry concrete mixture containing fly ash is calculated from the minimum-void concept, and the dry mixing method is selected to process the mix. The test results reveal that segments with homogeneous quality and excellent engineering properties can be obtained by a 3-min high-pressure compaction process and 1- to 2-day moist-curing. From experience, the automated process of production is also feasible, and it is proposed that the properties of segment using compaction and similarity technology from this study have great possibilities in lunar base construction.

During the NASA 90-day study, in response to the President's statement on the space exploration initiative, the Jet Propulsion Laboratory conducted a study of potential astronomical observatories that could be situated on the lunar surface in conjunction with the lunar outpost. The scientific objectives were derived from the four NASA discipline management and operations working groups, several special workshops and symposia on lunar astrophysics, and the NASA Office of Space Science and Applications (OSSA). The overriding premise in selecting and defining the lunar observatories was that the moon must provide some unique advantage in performance, cost, or other significant parameter, such that the experiment could be executed better there than anywhere else. The unique properties of lunar siting include 1/6 gravity, a large stable platform, long continuous viewing times, and low nighttime temperatures. The four observatories were: a seven-element optical interferometer with a 1- to 2-km baseline; a seven-element submillimeter interferometer with coherent detectors and a 1-km baseline; a very low-frequency interferometer (ó 30 MHz) with 100 elements and a 200-km baseline on the lunar far side; and a gravitational wave detector with two 50-km arms, perhaps operating in conjunction with an earth-based gravitational detector. Advanced technology needs associated with the four observatories have been identified and include advances in optical delay lines and beam combiners, coherent heterodyne detectors, instrument cryogenic systems, and methods for construction on the moon, such as building foundations, trenching building roads, etc. In particular, the problems of construction and civil engineering commonplace on earth present a new class of problem for the lunar surface. The paper addresses some of these civil engineering needs and suggests precursor experiments that should be done to provide a firm basis for the construction of astronomical observatories on the moon.