The Nanogranular Behavior of C-S-H at Elevated Temperatures (up to 700 °C)

Cement-based materials are non-combustible, but the complex chemo-physical mechanisms that drive the thermal degradation of the mechanical properties (stiffness, strength) at elevated temperatures are still an enigma that have deceived many decoding attempts. This paper presents, for the first time, results from a new experimental technique that allows rational assessment of the evolution of the nano-mechanical behavior of cement paste at elevated temperatures. Specifically, the thermal degradation of the 2 distinct calcium-silicate hydrate (C-S-H) phases, Low Density (LD) C-S-H and High Density (HD) C-S-H, is assessed based on a statistical analysis of massive nanoindentation tests. From a combination of nanoindentation, thermogravimetry, and micromechanical modeling, a new mechanism is identified--the thermally induced change of the packing density of the 2 C-S-H phases, as the dominant mechanism that drives the thermal degradation of cementitious materials. It is argued that this loosening of the packing density results from shrinkage of C-S-H nanoparticles that occurs at high temperatures, most likely due to loss of chemically bound water.

  • Availability:
  • Supplemental Notes:
    • Abstract reprinted with permission from Elsevier
  • Authors:
    • DeJong, Matthew J
    • Ulm, Franz-Josef
  • Publication Date: 2007-1

Language

  • English

Media Info

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Filing Info

  • Accession Number: 01042257
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Feb 26 2007 2:32AM