Upscaling quasi-brittle strength of cement paste and mortar: A multi-scale engineering mechanics model

It is well known from experiments that the uniaxial compressive strength of cementitious materials depends linearly on the degree of hydration, once a critical hydration degree has been surpassed. It is less known about the microstructural material characteristics which drive this dependence, nor about the nature of the hydration degree-strength relationship before the aforementioned critical hydration degree is reached. In order to elucidate the latter issues, the authors here present a micromechanical explanation for the hydration degree-strength relationships of cement pastes and mortars covering a large range of compositions: Therefore, the authors envision, at a scale of fifteen to twenty microns, a hydrate foam (comprising spherical water and air phases, as well as needle-shaped hydrate phases oriented isotropically in all space directions), which, at a higher scale of several hundred microns, acts as a contiguous matrix in which cement grains are embedded as spherical clinker inclusions. Mortar is represented as a contiguous cement paste matrix with spherical sand grain inclusions. Failure of the most unfavorably stressed hydrate phase is associated with overall (quasi-brittle) failure of cement paste or mortar. After careful experimental validation, the study's modeling approach strongly suggests that it is the mixture- and hydration degree-dependent load transfer of overall, material sample-related, uniaxial compressive stress states down to deviatoric stress peaks within the hydrate phases triggering local failure, which determines the first nonlinear, and then linear dependence of quasi-brittle strength of cementitious materials on the degree of hydration.

• Record URL:
  https://doi.org/10.1016/j.cemconres.2011.01.010
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/00088846
• Supplemental Notes:
  • Abstract reprinted with permission from Elsevier.
• Authors:
  • Pichler, Bernhard
  • Hellmich, Christian
• Publication Date: 2011-5

Language

• English

Media Info

• Media Type: Print
• Features: Figures; References; Tables;
• Pagination: pp 467-476
• Serial:
  • Cement and Concrete Research
  • Volume: 41
  • Issue Number: 5
  • Publisher: Elsevier
  • ISSN: 0008-8846
  • Serial URL: http://www.sciencedirect.com/science/journal/00088846

Subject/Index Terms

• TRT Terms: Brittleness; Cement mortars; Cement paste; Hydration; Microstructure; Strength of materials
• Uncontrolled Terms: Compressive stress; Engineering models; Materials characterization; Matrix analysis; Mechanical models; Micromechanical models
• Subject Areas: Highways; Materials;

Filing Info

• Accession Number: 01338240
• Record Type: Publication
• Files: TRIS
• Created Date: Apr 29 2011 7:36AM