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Journal of Materials Science

, Volume 31, Issue 17, pp 4573–4580 | Cite as

Thermodynamical approach to the brittle fracture of dry plasters

  • P. Coquard
  • R. Boistelle
Article

Abstract

The evolution of the fracture toughness, Klc, and fracture energy, Glc, of set plasters was determined on notched beams as a function of sample porosity, P, and characteristic size, W. Toughness was found to decrease with decreasing crack width. For set plasters of 57.7% porosity, the lowest toughness measured was Klc=0.13 MPa m1/2 for a crack width of 0.2 mm. For this crack width, fracture toughness and fracture energy linearly changed with porosity: Klc=0.5 1–1.3 P) MPa m1/2 and Glc= 13.47 (1–1.12 P) Jm−2. Dense plasters were more difficult to break than porous ones. The fracture energies were affected by the velocity of the fracture propagation, which induces damaging and multicracking of the material, so that the roughly calculated chemical surface energy of set plaster was too high. After correction it was estimated to be 0.4 J m −2. Finally, because toughness increased with increasing sample size, it was concluded that fracture toughness and energy were not intrinsic parameters of the material. On the other hand, for our sample porosities and sizes, the reduced rupture force, FruptW−0.65 is a constant and seems to be a characteristic parameter of the mechanical resistance of set plaster beams.

Keywords

Porosity Brittle Fracture Toughness Chemical Surface Brittle Fracture 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Chapman & Hall 1996

Authors and Affiliations

  • P. Coquard
    • 1
  • R. Boistelle
    • 1
  1. 1.Centre de Recherche sur les Mécanismes de la Croissance CristallineCNRSMarseille cedex 09France

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