Geopolymers are inorganic cementitious binders produced by polymeric reaction between an aluminosilica rich material and an alkali metal hydroxide/silicate liquid, forming a binding gel, which can be used to encapsulate fine and coarse aggregates to produce concrete. While earth-based applications utilize commonly available materials, such as metakaolin, fly ash, or even rice husk, researchers have reproduced lunar regolith to make geopolymer concrete specimens ('Lunamer') by activating the regolith with alkali liquid. Geopolymer binder technology presents superior mechanical and thermal performance, and has been shown to be compatible with an abundantly available lunar resource (lunar regolith). The highly conductive geopolymer has been enhanced further for use in electromagnetic (EMI) shielding and electrostatic discharge (ESD) applications. Conductive filler materials (carbon fibers and/or carbon black) were added to the geopolymer matrix. Impedance measurements were performed to determine the conductivity value of different conductive composite formulations. Results indicated that conductive geopolymer matrices are very effective in blocking electromagnetic waves of frequencies greater than 1 GHz. Therefore, to understand space-based applications, next steps should include characterizing radiation shielding effectiveness of geopolymer and 'Lunamer' concrete.
The purpose of this project is to develop lunar regolith based geopolymer concrete and perform differential shielding studies on various geopolymer formulations to determine if sufficient protection from radiation in space environments can be enabled. For the initial testing of these concrete matrices, a variety of locally-available radiation sources will be used. As part of the proposed work, geopolymer and 'Lunamer' concrete matrices will be constructed and their ability to shield radiation will be evaluated. The geopolymer matrices will be prepared using fly ash as the pre-curser, barite (BaSO4) and hematite (Fe2O3) as the aggregate and metallic chips, representing the state-of-the-art in Earth-based construction practices. The 'Lunamer' concrete matrices will be made using geopolymerized lunar regolith with entrained carbon fibers and carbon black for EMI shielding and metallic chips. These will include radiation energies within this range of biological interest, but will also include those of lower energies. While such low energy sources cannot be used to correlate the biological impact of high energy radiation, they do provide a useful tool to quantify the relative shielding behavior of different materials.More »
The geopolymer and “lunamer” binders will directly benefit NASA funded mission by providing radiative shielding that could be used for projected long-term space-based missions. Cosmic radiation is the critical obstacle preventing extended human space exploration. There is currently no practical application which can fully reproduce the shielding effect produced by the Earth’s strong magnetic field in combination with dense atmosphere. Since extended missions to the Moon and Mars are in the NASA’s Space Technology roadmap, a tremendous amount of research is therefore focused upon inventively finding ways that will reduce radiation exposure both in transit, and at the final destination in space. An innovative solution is to take advantage of the native shielding properties of the planetary material itself, and utilize and/or create subsurface structures with it. Additionally, the potential capability to create building materials in situ, almost entirely from materials that can be readily obtained from the surface of the moon or potentially other planets would also be enabled.More »
|Organizations Performing Work||Role||Type||Location|
|Stennis Space Center (SSC)||Lead Organization||NASA Center||Stennis Space Center, Mississippi|