REPLY TO DISCUSSION BY PETER J. TUMIDAJSKI OF THE PAPER "COLLOIDAL GRAPHITE AS AN ADMIXTURE IN CEMENT AND AS A COATING ON CEMENT FOR ELECTROMAGNETIC INTERFERENCE SHIELDING"

In this article, the original authors respond to a discussion of their study that investigated the use of graphite colloid as an admixture in cement and as a coating on cement for providing electromagnetic interference (EMI) shielding. In the study, the authors concluded that the graphite colloid as an admixture was ineffective for lowering the electrical resistivity of cement compared to carbon fibers and filaments. In the commentary, Tumidajski addressed three points made by the study's authors: graphite's use for shielding, presumably due to the skin effect; that a high shielding effectiveness does not imply a high electrical conductivity; and the very high values for the reported resistivities. The commentary author noted that with such low conductivities for the cement paste and cement-graphite paste, it is surprising that there is any appreciable electromagnetic attenuation. Cao and Chung reply that a material that exhibits low electrical conductivity does not necessarily exhibit poor shielding effectiveness, even in the case that reflection is the dominant mechanism of shielding. In the case of a cement-matrix composite containing graphic particles, the electromagnetic radiation interacts with each graphite particle while the interaction with the cement matrix is little. Thus, the skin depth for a graphite particle is relevant to the understanding of the effectiveness of the graphite particles in enhancing the shielding of the cement-matrix composite. Cao and Chung conclude that the values noted in the tables in Tumidajski's commentary are unreasonably low.

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    Elsevier

    The Boulevard, Langford Lane
    Kidlington, Oxford  United Kingdom  OX5 1GB
  • Authors:
    • Cao, Jiannong
    • Chung, DDL
  • Publication Date: 2005-3

Language

  • English

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  • Accession Number: 00989016
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 29 2005 12:00AM