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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.

Showing 1-5 of 21 Abstracts search results

Document: 

SP125-14

Date: 

May 1, 1991

Author(s):

Marvin E. Criswell and Willy Z. Sadeh

Publication:

Symposium Papers

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.

DOI:

10.14359/3782

Document: 

SP125-16

Date: 

May 1, 1991

Author(s):

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

Publication:

Symposium Papers

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.

DOI:

10.14359/3796

Document: 

SP125-19

Date: 

May 1, 1991

Author(s):

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

Publication:

Symposium Papers

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

DOI:

10.14359/3802

Document: 

SP125-20

Date: 

May 1, 1991

Author(s):

H. A. Franklin

Publication:

Symposium Papers

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

DOI:

10.14359/3806

Document: 

SP125-18

Date: 

May 1, 1991

Author(s):

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

Publication:

Symposium Papers

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.

DOI:

10.14359/2459

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