International Concrete Abstracts Portal

ABOUT THE INTERNATIONAL CONCRETE ABSTRACTS PORTAL

  • The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

International Concrete Abstracts Portal

Showing 1-10 of 21 Abstracts search results

Document: 

SP125-20

Date: 

May 1, 1991

Author(s):

H. A. Franklin

Publication:

Special Publication

Volume:

125

Abstract:

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

10.14359/3806


Document: 

SP125-19

Date: 

May 1, 1991

Author(s):

David Webb, Chris Shove, and T. D. Lin.

Publication:

Special Publication

Volume:

125

Abstract:

Presents the concept of Moonbase #1--its objectives, financial structure, facilities, functions, and scientific/engineering merits. In accordance with a Florida state goal of encouraging commercial enterprise, a consortium of corporations is in the proce

10.14359/3802


Document: 

SP125-18

Date: 

May 1, 1991

Author(s):

C. L. Hwang, R. Y. Lin, S. L. Shieh, and L. C. Lee

Publication:

Special Publication

Volume:

125

Abstract:

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.

10.14359/2459


Document: 

SP125-17

Date: 

May 1, 1991

Author(s):

A. Mishulovich, Tung D. Lin, S. W. Tresouthick, and P. B. West

Publication:

Special Publication

Volume:

125

Abstract:

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.

10.14359/2450


Document: 

SP125-16

Date: 

May 1, 1991

Author(s):

Joseph J. O'Gallagher and T. D. Lin

Publication:

Special Publication

Volume:

125

Abstract:

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.

10.14359/3796


Document: 

SP125-15

Date: 

May 1, 1991

Author(s):

Donald M. Burt

Publication:

Special Publication

Volume:

125

Abstract:

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.

10.14359/2435


Document: 

SP125-14

Date: 

May 1, 1991

Author(s):

Marvin E. Criswell and Willy Z. Sadeh

Publication:

Special Publication

Volume:

125

Abstract:

Early in the next century, humans will return to the surface of the moon for stays of increasingly longer duration. Many civil engineering challenges must be addressed so that these twenty-first century pioneers will have the shelter and life-support systems needed to survive and thrive in a largely benign but, in some ways, hostile environment. Depending on the stage of the lunar presence, different structures and processes will be feasible. Reliance on lunar resources, including manufactured forms such as lunar concrete, will become more important as the base size and maturity grows. It is the task of the universities in these endeavors to provide the basic knowledge to help meet these challenges and to produce enthusiastic and well-prepared graduates who can best continue to develop the solutions needed to support the expansion of humans into space. Educational programs in space civil engineering now undergoing development at Colorado State University under a NASA space grant college program are described. An undergraduate option that supplements the existing civil engineering program through a cluster of classes that can be taken within the existing elective structure is being developed. Concepts for an MS graduate program are also outlined.

10.14359/3782


Document: 

SP125-13

Date: 

May 1, 1991

Author(s):

Richard M. Drake

Publication:

Special Publication

Volume:

125

Abstract:

It has been proposed that a large pressurized shirt sleeve environment assembly facility would be useful during all phases of lunar outpost development. This article discusses the use of such a facility during later phases of outpost development when use of native materials is maximized. The principle benefits from the use of a large pressurized facility are that workers needn't wear cumbersome, restrictive space suits and concrete needn't be cured in the vacuum environment of the moon. A specific assembly facility concept is presented and its conversion to a lunar precast concrete plant is discussed.

10.14359/3774


Document: 

SP125-12

Date: 

May 1, 1991

Author(s):

S. W. Johnson, G. J. Taylor, J. P. Wetzel, and J. O. Burns

Publication:

Special Publication

Volume:

125

Abstract:

The moon offers a stable platform with excellent visual conditions for astronomical observations. Some troublesome aspects of the lunar environment must be overcome to realize the full potential of the moon as an observatory site. Mitigation of negative effects of vacuum, thermal radiation, dust, and micrometeorite impact is feasible with careful engineering and operational planning. Shields against impact, dust, and solar radiation must be developed. Means of restoring degraded surfaces are probably essential for optical and thermal control surfaces deployed on long-lifetime lunar facilities. Precursor missions should be planned to validate and enhance the understanding of the lunar environment (e.g., dust behavior with and without human presence) and to determine environmental effects on surfaces and components. Precursor missions should generate data useful in establishing keepout zones around observatory facilities where rocket launches and landings, mining, and vehicular traffic could be detrimental to observatory operation. If lunar concrete becomes available, it could be a material of choice for observatory foundation construction. For concrete to be a viable choice, its production and use must be compatible with the observatories' needs for clean, precision optics, and for an environment free of dust, shock, vibration, and outgassing. It must also be economically competitive with alternative construction techniques.

10.14359/3763


Document: 

SP125-11

Date: 

May 1, 1991

Author(s):

Philip Chow and T. Y. Lin

Publication:

Special Publication

Volume:

125

Abstract:

Conventional structural engineering philosophy and experience can be inappropriate when it comes to designing structures for the moon. This paper illustrates the authors' adaptation of design philosophy for concrete, which involves changing the whole value system for this material. Far from being readily available, common, and plentiful, concrete will be an exotic and precious material on the moon. The use of concrete is proposed for such efficient structures as thin shell rather than the more common planar structures more suitable for earth. The structure containing one atmospheric pressure inside must be pressurized to resist such pressure, and a new value system must be derived.

10.14359/3753


123

Results Per Page