Monday, October 20, 2008

Waterless Concrete, Just add S to Regolith

Dr. Houssam A. Toutanji of the University of Alabama at Huntsville, Department of Civil and Environmental Engineering is a true innovator in the ancient arts of public works. Applying his skills to the dry, dusty and radiation-baked lunar surface, he now certain shelter and cost savings can be harvested in situ on the Moon, mixing waterless concrete.

A report three years ago from UAH on Toutanji's work, said, "He has spent his research career studying the characteristics of concrete, including the last four years researching the possibility of making concrete on the moon. During those four years, he has had a share of scientists telling him that he was wasting his time — America would never go back to the moon. A wide grin spreads across his face. "Those are the same scientists who are calling me, emailing me and asking me about my research today," he said.

Another three year later, Toutanji has apparently made some breakthroughs, publishing an article, according to Science Daily, "that will demonstrate a concept of creating concrete structures on the lunar surface without the use of water."

Traditional concrete comprises a binder — cement and water — mixed with aggregates. While some parts of the Moon may have water, that resource may be more valuable for astronaut’s consumption rather than building structures.

His research shows that those astronauts can turn to a new type of waterless concrete that uses lunar soil as the aggregate and sulfur as a binding agent. Years of work must be paying off. In the recent past, Toutanji expressed concerns about sublimation, the slow deterioration of materials mostly from rapid thermal expansion and contraction and radiation-induced space weathering.

Toutanji was co-author in 2007 of an article along with Dr. Richard N. Grugel, a geological engineer at NASA’s Marshall Space Flight Center. According to the abstract, Toutanji & Grugel wrote:

Melting sulfur and mixing it with an aggregate to form “concrete” is commercially well established and constitutes a material that is particularly well-suited for use in corrosive environments. Discovery of the mineral troilite (FeS) on the moon poses the question of extracting the sulfur for use as a lunar construction material. This would be an attractive alternative to conventional concrete as it does not require water. However, the viability of sulfur concrete in a lunar environment, which is characterized by lack of an atmosphere and extreme temperatures, is not well understood. Here it is assumed that the lunar ore can be mined, refined, and the raw sulfur melded with appropriate lunar regolith to form, for example, bricks. This study evaluates pure sulfur and two sets of small sulfur concrete samples that have been prepared using JSC-1 lunar stimulant and SiO2 powder as aggregate additions. Each set was subjected to extended periods in a vacuum environment to evaluate sublimation issues. Results from these experiments are presented and discussed within the context of the lunar environment.

No comments: